Splice variants of 461 transcription factor loci were analyzed using a new database of splice variants in the mouse transcriptome, MouSDB3, providing quantitative evidence that alternative splicing preferentially adds or deletes domains important to the DNA-binding function of the TFs.

Background Alternative splicing is a widespread mechanism involved in regulation of gene expression, which enables production of many structurally and functionally different forms of proteins from a single gene, adding to the complexity of the genomes [ 1 - 3 ]. Different mRNA transcripts of a gene can be expressed in different tissues or developmental stages or physiological conditions [ 4 , 5 ]. An expanding body of expressed sequence data from the human and mouse genomes indicates that alternative splicing is an important mechanism in creating protein diversity, and adds to functional complexity encoded in eukaryotic genomes. Earlier studies indicate that at least 50% of the genes in the human genome are alternatively spliced [ 6 ]. Examples include the vast majority of immune system and nervous system genes [ 7 ]. Comprehensive analysis of alternative splicing is essential to understand fully the proteomes of organisms [ 8 ]. Several reports have indicated that variant splice forms result in proteins with different functions. These can range from minimal changes in function to absolutely opposite functions. For example, the cAMP-response element modulator has three different isoforms with entirely different DNA-binding domains, which are all transcription activators. On the other hand, isoforms of the human transcription factor AML1 function both as positive and as negative regulators of transcription [ 9 ]. However, for the majority of genes, the functional significance of alternative splicing is still not known [ 8 ]. Transcription is a critical process that specifies the mRNAs and the proteins expressed within a cell. Expression of a given gene is dependent on the interactions of different transcription factors and their cofactors with the regulatory regions of that gene. These transcription factors are in turn regulated by processes that include interaction with other proteins and signaling cascades [ 9 ]. Alternative splicing is a mechanism that regulates transcription factor (TF) activity by generating a variety of protein isoforms from a single gene. As noted by Lopez, alternative splicing can affect TF structure in two primary ways [ 9 ]: alterations can be in the DNA-binding domains affecting their affinity or specificity; or alterations can modulate interactions of transcription factors with their cofactors. Such changes have been observed experimentally to alter specificity or binding strength or to switch between activator and repressor isoforms of the same TF [ 10 ]. TF isoforms can have stage-specific and tissue-specific expression patterns throughout the development of an organism [ 9 ]. Little is known about the tissue specificity of alternative splicing [ 11 ]. In this paper, we use an integrated approach to analyze DNA and protein sequence data jointly to determine the potential effect of alternative splicing on protein structure and function. We perform a detailed analysis of tissue-specific distribution of alternatively spliced mouse TFs to gain biologically meaningful insights into regulation of gene expression by alternative splicing.
Background
Alternative splicing is a widespread mechanism involved in regulation of gene expression, which enables production of many structurally and functionally different forms of proteins from a single gene, adding to the complexity of the genomes [ 1 - 3 ]. Different mRNA transcripts of a gene can be expressed in different tissues or developmental stages or physiological conditions [ 4 , 5 ].An expanding body of expressed sequence data from the human and mouse genomes indicates that alternative splicing is an important mechanism in creating protein diversity, and adds to functional complexity encoded in eukaryotic genomes. Earlier studies indicate that at least 50% of the genes in the human genome are alternatively spliced [ 6 ]. Examples include the vast majority of immune system and nervous system genes [ 7 ].Comprehensive analysis of alternative splicing is essential to understand fully the proteomes of organisms [ 8 ]. Several reports have indicated that variant splice forms result in proteins with different functions. These can range from minimal changes in function to absolutely opposite functions. For example, the cAMP-response element modulator has three different isoforms with entirely different DNA-binding domains, which are all transcription activators. On the other hand, isoforms of the human transcription factor AML1 function both as positive and as negative regulators of transcription [ 9 ]. However, for the majority of genes, the functional significance of alternative splicing is still not known [ 8 ].Transcription is a critical process that specifies the mRNAs and the proteins expressed within a cell. Expression of a given gene is dependent on the interactions of different transcription factors and their cofactors with the regulatory regions of that gene. These transcription factors are in turn regulated by processes that include interaction with other proteins and signaling cascades [ 9 ].Alternative splicing is a mechanism that regulates transcription factor (TF) activity by generating a variety of protein isoforms from a single gene. As noted by Lopez, alternative splicing can affect TF structure in two primary ways [ 9 ]: alterations can be in the DNA-binding domains affecting their affinity or specificity; or alterations can modulate interactions of transcription factors with their cofactors. Such changes have been observed experimentally to alter specificity or binding strength or to switch between activator and repressor isoforms of the same TF [ 10 ]. TF isoforms can have stage-specific and tissue-specific expression patterns throughout the development of an organism [ 9 ]. Little is known about the tissue specificity of alternative splicing [ 11 ].In this paper, we use an integrated approach to analyze DNA and protein sequence data jointly to determine the potential effect of alternative splicing on protein structure and function. We perform a detailed analysis of tissue-specific distribution of alternatively spliced mouse TFs to gain biologically meaningful insights into regulation of gene expression by alternative splicing.Results Definitions For our joint DNA-protein analysis described here, we developed MouSDB3 [ 12 ], which identifies, classifies, computes, stores and answers queries about splice variants within the mouse genome. As described in Materials and methods, MouSDB3 uses the mouse genome and expressed sequences in GenBank [ 13 ] and dbEST [ 14 ] to compute splice variants of mouse transcripts organized by genomic loci. This section provides definitions of terms used in MouSDB3 and in the joint DNA-protein analysis method described here. A 'transcript' is a sequence transcribed from the genomic DNA sequence. MouSDB3 is restricted to transcripts with at least one splice junction. A 'locus' is a genomic region that includes a set of overlapping transcripts mapped to the genome such that a transcript appears in only one locus and all transcripts whose genome coordinates overlap by at least one nucleotide are included in the locus. Within a locus, a 'cassette exon' is completely included in some transcripts and completely excluded in others. A 'length variant exon' has alternative 5' or 3' splice sites, or both, in different transcripts. An exon can be both length variant and cassette. A 'variant exon' is either cassette or length variant or both. We consider an exon whose number of nucleotides is a multiple of three and which starts at the first base of a codon to be an 'in-frame exon'. Such exons do not introduce an amino-acid substitution or a stop codon when skipped, unless they are terminal exons within the coding sequence. A 'genomic exon' is an uninterrupted series of nucleotides, each of which is mapped to a transcript. By this definition the genomic exon for a length variant exon reflects the outermost splice sites. A 'cluster' is the set of transcripts that map to a locus. A 'variant cluster' contains one or more variant exons. An 'invariant cluster' has no variant exons. MouSDB3 cluster analysis Our cluster analysis revealed that out of the 461 TF clusters, 62% are variant, compared to 29% of all genes in MouSDB3 (Table  1 ). The majority (62%) of the variation in TFs is due to cassette exons, which is comparable to cassette-exon distribution in the entire transcriptome (68% of the variant exons in all loci are cassette). As the majority of alternative splicing is due to cassette exons, we focus on these exons for our analyses. Cassette exon analysis We screened the 287 variant TF clusters for the presence of cassette exons within coding sequences. We categorized MouSDB3 transcripts into three categories with respect to each cassette exon within a cluster. Category 1 transcripts contain the exon and are referred to as 'long transcripts'. Category 2 transcripts skip the exon and are referred to as 'short transcripts'. Category 3 transcripts do not overlap with the cassette exon due to 5' or 3' truncations. In our structural analysis, we computationally delete in-frame cassette exons from Category 1 transcripts to produce an 'altered transcript'. Figure  1  displays a MouSDB3 cluster and illustrates these categories. The 287 variant TF loci contain 324 cassette exons of which 23% (76 exons) are in-frame. Only 11% of cassette exons are expected to be multiples of three and in codon position 1 randomly. The twofold difference between expected and observed numbers indicates a bias towards in-frame cassette exons. The exons which are a multiple of three and in codon position 2 and 3 comprise 10% and 7%, respectively. When deleted, these exons introduce an amino-acid substitution to the sequence. As exons which are a multiple of three starting at codon position 1 are enriched and do not introduce an amino-acid substitution when deleted, our study focuses on these exons only. As shown in Figure  2 , of the 76 in-frame cassette exons, 66 have domain architectures predicted by SMART. The remaining 10 exons are either from transcripts with too short sequences or these transcripts do not have any of the domains annotated in SMART. Of the 66 in-frame cassette exons, 80% (53) induce a domain-structure alteration to the protein when skipped. Of these 53 structure-altering exons, 68% are within coding regions for the domains that are important for TF activity, such as DNA-binding or activation domains. The remaining 32% (17) of exons are proximal to the computed domain boundaries; that is, the domain is coded by the upstream or the downstream neighboring exon of the cassette exon. When the cassette exon is removed, the sequence no longer meets the computational criteria for the domain (Figure  2 ). Assessing domain architecture alterations SMART [ 15 , 16 ] and Pfam [ 17 , 18 ] entries for the altered domains revealed that 75% of the domains affected by alternative splicing with known functions are DNA-binding domains. The names of all altered domains and links to their annotated biological functions are provided on our web page [ 19 ]. There we provide the 53 in-frame cassette exons (shown in Figure  2 ), which alter the domain architecture of their transcripts when skipped. Links to MouSDB3 clusters containing these transcripts and links to their GenBank entries are provided. In addition, we provide the names of the domains altered by these 53 exons as active links to their SMART and Pfam annotations. All sequences for long transcripts, altered transcripts and in-frame cassette exons are provided as links to fasta files on the same web page. Our domain-alteration results correlate with recent findings of Resch  et al . [ 20 ], who show that alternative splicing preferentially removes certain domains more frequently. Tissue-distribution analysis Part two of our analysis assessed the tissue distribution of alternatively spliced transcription factors. We chose 18 tissues from the existing libraries in MouSDB3 on the basis of the fact that they contain both variant and invariant transcripts annotated as TFs. There are a total of 1,413 library names in MouSDB3 imported from expressed sequence records in GenBank and dbEST. Of these, 328 are ambiguous in that they list several different tissues or cell types for a single library, such as 'mixture of brain and testis' or no tissues at all, such as 'embryo or carcinoma'. For the work described here we did not include tissue information from such ambiguous libraries. There are a total of 95 libraries in MouSDB3 for which there are TF transcripts. In addition, to account for library ambiguities within these 95 libraries, we pooled different parts of a tissue into one library. For example, the term 'brain' corresponds to all parts of the brain found in MouSDB3, including cerebellum, thalamus, hippocampus and 16 other libraries. When analyzing the tissue distribution of all genes, only the libraries that contain TF transcripts have been used. Transcript counts within variant loci for 18 pooled libraries indicated that in 14 of the 18 analyzed tissues, the proportion of TFs that are variant is higher than the proportion of all genes that are variant (Figure  3a ). This finding, together with the observation that 62% of TF loci are variant, indicates the widespread impact of alternative splicing on regulation of gene expression via TFs. For each of the 18 tissues in Figure  3a , we compared the proportion of TFs that vary to the proportion of all genes that vary. As shown in Figure  3b , eight tissues exhibited more than twofold difference in variant TFs versus variant genes in total. (Note that values in Figure  3b  are base 2 logarithms of the ratios. Tissues with twofold differences have log 2  values above 1 on the graph). In salivary gland, skeletal muscle, urinary bladder and testis, the fold-differences are 8.7, 5.6, 3.8 and 3.0-fold respectively. Spinal cord, liver, adipose tissue and eye also exhibit more than twofold differences. These values are independent of the sampling depth of the transcripts from these tissues, as illustrated in Figures  4a  and  4b . Sampling depth is the number of transcripts sequenced per tissue (either a single library or a pooled library as in the case of 'brain'). Figure  4a  displays absolute numbers of variant TF transcripts and Figure  4b  displays absolute numbers of the entire variant transcripts of the transcriptome. In Figures  4a,b , tissues are presented along the  x -axis as in Figure  3b  for the reader's convenience. The correlation coefficient of the absolute numbers of TFs and the fold-differences between variant TFs and all genes is -0.13, indicating that they do not correlate. Likewise, the correlation coefficient of the absolute numbers of all genes and the fold-differences between variant TFs and all genes is -0.46. Additionally, the scatter-plots in Figures  4c,d  show that there is no correlation between the fold-differences and sampling depth. The datasets used in calculating the correlation coefficients can be found on our web page [ 19 ].
Results
Definitions For our joint DNA-protein analysis described here, we developed MouSDB3 [ 12 ], which identifies, classifies, computes, stores and answers queries about splice variants within the mouse genome. As described in Materials and methods, MouSDB3 uses the mouse genome and expressed sequences in GenBank [ 13 ] and dbEST [ 14 ] to compute splice variants of mouse transcripts organized by genomic loci. This section provides definitions of terms used in MouSDB3 and in the joint DNA-protein analysis method described here. A 'transcript' is a sequence transcribed from the genomic DNA sequence. MouSDB3 is restricted to transcripts with at least one splice junction. A 'locus' is a genomic region that includes a set of overlapping transcripts mapped to the genome such that a transcript appears in only one locus and all transcripts whose genome coordinates overlap by at least one nucleotide are included in the locus. Within a locus, a 'cassette exon' is completely included in some transcripts and completely excluded in others. A 'length variant exon' has alternative 5' or 3' splice sites, or both, in different transcripts. An exon can be both length variant and cassette. A 'variant exon' is either cassette or length variant or both. We consider an exon whose number of nucleotides is a multiple of three and which starts at the first base of a codon to be an 'in-frame exon'. Such exons do not introduce an amino-acid substitution or a stop codon when skipped, unless they are terminal exons within the coding sequence. A 'genomic exon' is an uninterrupted series of nucleotides, each of which is mapped to a transcript. By this definition the genomic exon for a length variant exon reflects the outermost splice sites. A 'cluster' is the set of transcripts that map to a locus. A 'variant cluster' contains one or more variant exons. An 'invariant cluster' has no variant exons.
Definitions
For our joint DNA-protein analysis described here, we developed MouSDB3 [ 12 ], which identifies, classifies, computes, stores and answers queries about splice variants within the mouse genome. As described in Materials and methods, MouSDB3 uses the mouse genome and expressed sequences in GenBank [ 13 ] and dbEST [ 14 ] to compute splice variants of mouse transcripts organized by genomic loci. This section provides definitions of terms used in MouSDB3 and in the joint DNA-protein analysis method described here. A 'transcript' is a sequence transcribed from the genomic DNA sequence. MouSDB3 is restricted to transcripts with at least one splice junction. A 'locus' is a genomic region that includes a set of overlapping transcripts mapped to the genome such that a transcript appears in only one locus and all transcripts whose genome coordinates overlap by at least one nucleotide are included in the locus. Within a locus, a 'cassette exon' is completely included in some transcripts and completely excluded in others. A 'length variant exon' has alternative 5' or 3' splice sites, or both, in different transcripts. An exon can be both length variant and cassette. A 'variant exon' is either cassette or length variant or both. We consider an exon whose number of nucleotides is a multiple of three and which starts at the first base of a codon to be an 'in-frame exon'. Such exons do not introduce an amino-acid substitution or a stop codon when skipped, unless they are terminal exons within the coding sequence. A 'genomic exon' is an uninterrupted series of nucleotides, each of which is mapped to a transcript. By this definition the genomic exon for a length variant exon reflects the outermost splice sites. A 'cluster' is the set of transcripts that map to a locus. A 'variant cluster' contains one or more variant exons. An 'invariant cluster' has no variant exons.MouSDB3 cluster analysis Our cluster analysis revealed that out of the 461 TF clusters, 62% are variant, compared to 29% of all genes in MouSDB3 (Table  1 ). The majority (62%) of the variation in TFs is due to cassette exons, which is comparable to cassette-exon distribution in the entire transcriptome (68% of the variant exons in all loci are cassette). As the majority of alternative splicing is due to cassette exons, we focus on these exons for our analyses.
MouSDB3 cluster analysis
Our cluster analysis revealed that out of the 461 TF clusters, 62% are variant, compared to 29% of all genes in MouSDB3 (Table  1 ). The majority (62%) of the variation in TFs is due to cassette exons, which is comparable to cassette-exon distribution in the entire transcriptome (68% of the variant exons in all loci are cassette). As the majority of alternative splicing is due to cassette exons, we focus on these exons for our analyses.Cassette exon analysis We screened the 287 variant TF clusters for the presence of cassette exons within coding sequences. We categorized MouSDB3 transcripts into three categories with respect to each cassette exon within a cluster. Category 1 transcripts contain the exon and are referred to as 'long transcripts'. Category 2 transcripts skip the exon and are referred to as 'short transcripts'. Category 3 transcripts do not overlap with the cassette exon due to 5' or 3' truncations. In our structural analysis, we computationally delete in-frame cassette exons from Category 1 transcripts to produce an 'altered transcript'. Figure  1  displays a MouSDB3 cluster and illustrates these categories. The 287 variant TF loci contain 324 cassette exons of which 23% (76 exons) are in-frame. Only 11% of cassette exons are expected to be multiples of three and in codon position 1 randomly. The twofold difference between expected and observed numbers indicates a bias towards in-frame cassette exons. The exons which are a multiple of three and in codon position 2 and 3 comprise 10% and 7%, respectively. When deleted, these exons introduce an amino-acid substitution to the sequence. As exons which are a multiple of three starting at codon position 1 are enriched and do not introduce an amino-acid substitution when deleted, our study focuses on these exons only. As shown in Figure  2 , of the 76 in-frame cassette exons, 66 have domain architectures predicted by SMART. The remaining 10 exons are either from transcripts with too short sequences or these transcripts do not have any of the domains annotated in SMART. Of the 66 in-frame cassette exons, 80% (53) induce a domain-structure alteration to the protein when skipped. Of these 53 structure-altering exons, 68% are within coding regions for the domains that are important for TF activity, such as DNA-binding or activation domains. The remaining 32% (17) of exons are proximal to the computed domain boundaries; that is, the domain is coded by the upstream or the downstream neighboring exon of the cassette exon. When the cassette exon is removed, the sequence no longer meets the computational criteria for the domain (Figure  2 ).
Cassette exon analysis
We screened the 287 variant TF clusters for the presence of cassette exons within coding sequences. We categorized MouSDB3 transcripts into three categories with respect to each cassette exon within a cluster. Category 1 transcripts contain the exon and are referred to as 'long transcripts'. Category 2 transcripts skip the exon and are referred to as 'short transcripts'. Category 3 transcripts do not overlap with the cassette exon due to 5' or 3' truncations. In our structural analysis, we computationally delete in-frame cassette exons from Category 1 transcripts to produce an 'altered transcript'. Figure  1  displays a MouSDB3 cluster and illustrates these categories.The 287 variant TF loci contain 324 cassette exons of which 23% (76 exons) are in-frame. Only 11% of cassette exons are expected to be multiples of three and in codon position 1 randomly. The twofold difference between expected and observed numbers indicates a bias towards in-frame cassette exons. The exons which are a multiple of three and in codon position 2 and 3 comprise 10% and 7%, respectively. When deleted, these exons introduce an amino-acid substitution to the sequence. As exons which are a multiple of three starting at codon position 1 are enriched and do not introduce an amino-acid substitution when deleted, our study focuses on these exons only.As shown in Figure  2 , of the 76 in-frame cassette exons, 66 have domain architectures predicted by SMART. The remaining 10 exons are either from transcripts with too short sequences or these transcripts do not have any of the domains annotated in SMART. Of the 66 in-frame cassette exons, 80% (53) induce a domain-structure alteration to the protein when skipped. Of these 53 structure-altering exons, 68% are within coding regions for the domains that are important for TF activity, such as DNA-binding or activation domains. The remaining 32% (17) of exons are proximal to the computed domain boundaries; that is, the domain is coded by the upstream or the downstream neighboring exon of the cassette exon. When the cassette exon is removed, the sequence no longer meets the computational criteria for the domain (Figure  2 ).Assessing domain architecture alterations SMART [ 15 , 16 ] and Pfam [ 17 , 18 ] entries for the altered domains revealed that 75% of the domains affected by alternative splicing with known functions are DNA-binding domains. The names of all altered domains and links to their annotated biological functions are provided on our web page [ 19 ]. There we provide the 53 in-frame cassette exons (shown in Figure  2 ), which alter the domain architecture of their transcripts when skipped. Links to MouSDB3 clusters containing these transcripts and links to their GenBank entries are provided. In addition, we provide the names of the domains altered by these 53 exons as active links to their SMART and Pfam annotations. All sequences for long transcripts, altered transcripts and in-frame cassette exons are provided as links to fasta files on the same web page. Our domain-alteration results correlate with recent findings of Resch  et al . [ 20 ], who show that alternative splicing preferentially removes certain domains more frequently.
Assessing domain architecture alterations
SMART [ 15 , 16 ] and Pfam [ 17 , 18 ] entries for the altered domains revealed that 75% of the domains affected by alternative splicing with known functions are DNA-binding domains. The names of all altered domains and links to their annotated biological functions are provided on our web page [ 19 ]. There we provide the 53 in-frame cassette exons (shown in Figure  2 ), which alter the domain architecture of their transcripts when skipped. Links to MouSDB3 clusters containing these transcripts and links to their GenBank entries are provided. In addition, we provide the names of the domains altered by these 53 exons as active links to their SMART and Pfam annotations. All sequences for long transcripts, altered transcripts and in-frame cassette exons are provided as links to fasta files on the same web page. Our domain-alteration results correlate with recent findings of Resch  et al . [ 20 ], who show that alternative splicing preferentially removes certain domains more frequently.et alTissue-distribution analysis Part two of our analysis assessed the tissue distribution of alternatively spliced transcription factors. We chose 18 tissues from the existing libraries in MouSDB3 on the basis of the fact that they contain both variant and invariant transcripts annotated as TFs. There are a total of 1,413 library names in MouSDB3 imported from expressed sequence records in GenBank and dbEST. Of these, 328 are ambiguous in that they list several different tissues or cell types for a single library, such as 'mixture of brain and testis' or no tissues at all, such as 'embryo or carcinoma'. For the work described here we did not include tissue information from such ambiguous libraries. There are a total of 95 libraries in MouSDB3 for which there are TF transcripts. In addition, to account for library ambiguities within these 95 libraries, we pooled different parts of a tissue into one library. For example, the term 'brain' corresponds to all parts of the brain found in MouSDB3, including cerebellum, thalamus, hippocampus and 16 other libraries. When analyzing the tissue distribution of all genes, only the libraries that contain TF transcripts have been used. Transcript counts within variant loci for 18 pooled libraries indicated that in 14 of the 18 analyzed tissues, the proportion of TFs that are variant is higher than the proportion of all genes that are variant (Figure  3a ). This finding, together with the observation that 62% of TF loci are variant, indicates the widespread impact of alternative splicing on regulation of gene expression via TFs. For each of the 18 tissues in Figure  3a , we compared the proportion of TFs that vary to the proportion of all genes that vary. As shown in Figure  3b , eight tissues exhibited more than twofold difference in variant TFs versus variant genes in total. (Note that values in Figure  3b  are base 2 logarithms of the ratios. Tissues with twofold differences have log 2  values above 1 on the graph). In salivary gland, skeletal muscle, urinary bladder and testis, the fold-differences are 8.7, 5.6, 3.8 and 3.0-fold respectively. Spinal cord, liver, adipose tissue and eye also exhibit more than twofold differences. These values are independent of the sampling depth of the transcripts from these tissues, as illustrated in Figures  4a  and  4b . Sampling depth is the number of transcripts sequenced per tissue (either a single library or a pooled library as in the case of 'brain'). Figure  4a  displays absolute numbers of variant TF transcripts and Figure  4b  displays absolute numbers of the entire variant transcripts of the transcriptome. In Figures  4a,b , tissues are presented along the  x -axis as in Figure  3b  for the reader's convenience. The correlation coefficient of the absolute numbers of TFs and the fold-differences between variant TFs and all genes is -0.13, indicating that they do not correlate. Likewise, the correlation coefficient of the absolute numbers of all genes and the fold-differences between variant TFs and all genes is -0.46. Additionally, the scatter-plots in Figures  4c,d  show that there is no correlation between the fold-differences and sampling depth. The datasets used in calculating the correlation coefficients can be found on our web page [ 19 ].
Tissue-distribution analysis
Part two of our analysis assessed the tissue distribution of alternatively spliced transcription factors. We chose 18 tissues from the existing libraries in MouSDB3 on the basis of the fact that they contain both variant and invariant transcripts annotated as TFs. There are a total of 1,413 library names in MouSDB3 imported from expressed sequence records in GenBank and dbEST. Of these, 328 are ambiguous in that they list several different tissues or cell types for a single library, such as 'mixture of brain and testis' or no tissues at all, such as 'embryo or carcinoma'. For the work described here we did not include tissue information from such ambiguous libraries. There are a total of 95 libraries in MouSDB3 for which there are TF transcripts. In addition, to account for library ambiguities within these 95 libraries, we pooled different parts of a tissue into one library. For example, the term 'brain' corresponds to all parts of the brain found in MouSDB3, including cerebellum, thalamus, hippocampus and 16 other libraries. When analyzing the tissue distribution of all genes, only the libraries that contain TF transcripts have been used.Transcript counts within variant loci for 18 pooled libraries indicated that in 14 of the 18 analyzed tissues, the proportion of TFs that are variant is higher than the proportion of all genes that are variant (Figure  3a ). This finding, together with the observation that 62% of TF loci are variant, indicates the widespread impact of alternative splicing on regulation of gene expression via TFs.For each of the 18 tissues in Figure  3a , we compared the proportion of TFs that vary to the proportion of all genes that vary. As shown in Figure  3b , eight tissues exhibited more than twofold difference in variant TFs versus variant genes in total. (Note that values in Figure  3b  are base 2 logarithms of the ratios. Tissues with twofold differences have log 2  values above 1 on the graph). In salivary gland, skeletal muscle, urinary bladder and testis, the fold-differences are 8.7, 5.6, 3.8 and 3.0-fold respectively. Spinal cord, liver, adipose tissue and eye also exhibit more than twofold differences. These values are independent of the sampling depth of the transcripts from these tissues, as illustrated in Figures  4a  and  4b . Sampling depth is the number of transcripts sequenced per tissue (either a single library or a pooled library as in the case of 'brain'). Figure  4a  displays absolute numbers of variant TF transcripts and Figure  4b  displays absolute numbers of the entire variant transcripts of the transcriptome. In Figures  4a,b , tissues are presented along the  x -axis as in Figure  3b  for the reader's convenience. The correlation coefficient of the absolute numbers of TFs and the fold-differences between variant TFs and all genes is -0.13, indicating that they do not correlate. Likewise, the correlation coefficient of the absolute numbers of all genes and the fold-differences between variant TFs and all genes is -0.46. Additionally, the scatter-plots in Figures  4c,d  show that there is no correlation between the fold-differences and sampling depth. The datasets used in calculating the correlation coefficients can be found on our web page [ 19 ].xIsoform heterogeneity We analyzed the presence of different isoforms of transcription factors within and across these 18 tissues. For this analysis we consider transcripts with coding sequence information only. We ignore variation due to 5' and 3' truncation of transcripts. We consider only cassette exons within coding sequences when assessing the differences between isoforms. Within a cluster we compute homogeneity and heterogeneity within a single tissue by checking for the transcripts from the same library and comparing the cassette exons within their coding sequences. If all transcripts from the same tissue contain the same cassette exons with same splice sites they are termed 'homogeneous within'. If the cassette exon distribution within the coding sequences of these transcripts differ, they are termed 'heterogeneous within'. We compute 'homogeneity across' and 'heterogeneity across' tissues in the same way by taking into account transcripts within the same clusters but from different libraries. As shown in Figure  5 , when heterogeneity to homogeneity ratios are compared within and across tissues, there is significantly more heterogeneity of isoforms across tissues than within a single tissue ( p -value = 0.04). This is true for both transcription factors and the rest of the genes in the mouse transcriptome. When single tissues are taken into account, TFs are more homogenous within each tissue analyzed. As shown in Figure  6 , heterogeneity to homogeneity ratios in all tissues are lower than 1, indicating that these tissues are more homogeneous in terms of TF isoforms. In fact, except for brain and thymus, all values for TFs are zero, hence the absence of blue bars from Figure  6 . When all genes are considered, heterogeneity to homogeneity ratios are also below 1, indicating homogeneity of isoforms of all genes within these tissues. However, there is still a significant difference in heterogeneity to homogeneity ratios between TF isoforms and isoforms of all genes: TFs are significantly more homogeneous within single tissues when compared to all genes ( p -value = 0.02). (The data used in calculating the homogeneity and heterogeneity values can be found on our web page [ 19 ].) Figures  5  and  6  show that the majority of TF isoforms and the isoforms of all alternatively spliced genes differ across tissues: within a given single tissue there generally is only one isoform. These data indicate the presence of tissue-specific alternative splicing throughout the mouse transcriptome. In addition, our findings indicate expression of different TF isoforms in different tissues. This implies contribution of alternative splicing to regulation of gene expression in a tissue-specific manner by controlling activation or repression of different sets of genes in different tissues via variant TF isoforms. These data have significant implications in further understanding the regulation of tissue-specific gene expression and control of transcription.
Isoform heterogeneity
We analyzed the presence of different isoforms of transcription factors within and across these 18 tissues. For this analysis we consider transcripts with coding sequence information only. We ignore variation due to 5' and 3' truncation of transcripts. We consider only cassette exons within coding sequences when assessing the differences between isoforms. Within a cluster we compute homogeneity and heterogeneity within a single tissue by checking for the transcripts from the same library and comparing the cassette exons within their coding sequences. If all transcripts from the same tissue contain the same cassette exons with same splice sites they are termed 'homogeneous within'. If the cassette exon distribution within the coding sequences of these transcripts differ, they are termed 'heterogeneous within'. We compute 'homogeneity across' and 'heterogeneity across' tissues in the same way by taking into account transcripts within the same clusters but from different libraries. As shown in Figure  5 , when heterogeneity to homogeneity ratios are compared within and across tissues, there is significantly more heterogeneity of isoforms across tissues than within a single tissue ( p -value = 0.04). This is true for both transcription factors and the rest of the genes in the mouse transcriptome.pWhen single tissues are taken into account, TFs are more homogenous within each tissue analyzed. As shown in Figure  6 , heterogeneity to homogeneity ratios in all tissues are lower than 1, indicating that these tissues are more homogeneous in terms of TF isoforms. In fact, except for brain and thymus, all values for TFs are zero, hence the absence of blue bars from Figure  6 . When all genes are considered, heterogeneity to homogeneity ratios are also below 1, indicating homogeneity of isoforms of all genes within these tissues. However, there is still a significant difference in heterogeneity to homogeneity ratios between TF isoforms and isoforms of all genes: TFs are significantly more homogeneous within single tissues when compared to all genes ( p -value = 0.02). (The data used in calculating the homogeneity and heterogeneity values can be found on our web page [ 19 ].)pFigures  5  and  6  show that the majority of TF isoforms and the isoforms of all alternatively spliced genes differ across tissues: within a given single tissue there generally is only one isoform. These data indicate the presence of tissue-specific alternative splicing throughout the mouse transcriptome. In addition, our findings indicate expression of different TF isoforms in different tissues. This implies contribution of alternative splicing to regulation of gene expression in a tissue-specific manner by controlling activation or repression of different sets of genes in different tissues via variant TF isoforms. These data have significant implications in further understanding the regulation of tissue-specific gene expression and control of transcription.Discussion Through integrated analyses of DNA and protein sequences for TF genes, we show that alternative splicing of TFs are more prevalent in the entire mouse transcriptome and in specific tissues when compared to alternatively spliced forms of all the genes. In 78% of the tissues analyzed, higher proportions of TFs exhibit alternative splicing compared to all the genes in the mouse transcriptome. This result, along with the finding that 62% of TF loci are variant, indicates the widespread impact of alternative splicing on regulation of TF function. We also show that alternative splicing changes TF structure by adding or deleting domains. This study reveals that 80% of alternatively spliced TFs have different domain architectures due to introduction of an in-frame cassette exon by alternative splicing. Of the altered domains, 75% have a role in DNA binding. These findings provide quantitative evidence for the role of alternative splicing in controlling the presence of domains in the proteins. They also suggest that alternative splicing might regulate TF activity by changing the architecture of the DNA-binding domains of these proteins. Our analyses revealed that within a single tissue there generally is only one TF isoform, and that across tissues, isoforms differ. This finding indicates tissue specificity of alternatively spliced TFs and suggests that TFs might regulate gene expression in a tissue-specific manner by having different isoforms in different tissues. These findings further indicate the role of alternative splicing in regulation of tissue-specific gene expression. Activation and repression of different sets of genes within different tissues can be regulated through variant TF isoforms created by alternative splicing. These findings will significantly aid further understanding of control of transcription and tissue-specific gene expression. In addition, our study shows that all variant loci in the mouse transcriptome display isoform homogeneity within single tissues and heterogeneity across tissues. This finding demonstrates the presence of tissue-specific alternative splicing across the mouse transcriptome and greatly expands the knowledge on the tissue specificity of alternatively spliced genes.
Discussion
Through integrated analyses of DNA and protein sequences for TF genes, we show that alternative splicing of TFs are more prevalent in the entire mouse transcriptome and in specific tissues when compared to alternatively spliced forms of all the genes. In 78% of the tissues analyzed, higher proportions of TFs exhibit alternative splicing compared to all the genes in the mouse transcriptome. This result, along with the finding that 62% of TF loci are variant, indicates the widespread impact of alternative splicing on regulation of TF function.We also show that alternative splicing changes TF structure by adding or deleting domains. This study reveals that 80% of alternatively spliced TFs have different domain architectures due to introduction of an in-frame cassette exon by alternative splicing. Of the altered domains, 75% have a role in DNA binding. These findings provide quantitative evidence for the role of alternative splicing in controlling the presence of domains in the proteins. They also suggest that alternative splicing might regulate TF activity by changing the architecture of the DNA-binding domains of these proteins.Our analyses revealed that within a single tissue there generally is only one TF isoform, and that across tissues, isoforms differ. This finding indicates tissue specificity of alternatively spliced TFs and suggests that TFs might regulate gene expression in a tissue-specific manner by having different isoforms in different tissues. These findings further indicate the role of alternative splicing in regulation of tissue-specific gene expression. Activation and repression of different sets of genes within different tissues can be regulated through variant TF isoforms created by alternative splicing. These findings will significantly aid further understanding of control of transcription and tissue-specific gene expression. In addition, our study shows that all variant loci in the mouse transcriptome display isoform homogeneity within single tissues and heterogeneity across tissues. This finding demonstrates the presence of tissue-specific alternative splicing across the mouse transcriptome and greatly expands the knowledge on the tissue specificity of alternatively spliced genes.Conclusions Overall, our study provides quantitative evidence for the effect of alternative splicing on protein structure and sheds light on how alternative splicing might regulate transcription factor function in a tissue-specific manner. This, in turn, reveals the contribution of alternative splicing to regulation of gene expression via tissue-specific TF isoforms. The work described here implies that future high-throughput screens of gene expression analyses should be sensitive to multiple alternatively spliced forms of TFs. Because gene-expression arrays are intended to measure transcription, the next generation of arrays should contain probes specific to all known isoforms of genes represented on the arrays. Given that alternatively spliced exons are highly conserved across species [ 21 , 22 ], it would be of further interest to extend this study to other organisms. Strong sequence homology between mouse, human and rat exons suggests that a comparative analysis of human, mouse and rat TF variations will be a natural extension of the studies described here.
Conclusions
Overall, our study provides quantitative evidence for the effect of alternative splicing on protein structure and sheds light on how alternative splicing might regulate transcription factor function in a tissue-specific manner. This, in turn, reveals the contribution of alternative splicing to regulation of gene expression via tissue-specific TF isoforms. The work described here implies that future high-throughput screens of gene expression analyses should be sensitive to multiple alternatively spliced forms of TFs. Because gene-expression arrays are intended to measure transcription, the next generation of arrays should contain probes specific to all known isoforms of genes represented on the arrays. Given that alternatively spliced exons are highly conserved across species [ 21 , 22 ], it would be of further interest to extend this study to other organisms. Strong sequence homology between mouse, human and rat exons suggests that a comparative analysis of human, mouse and rat TF variations will be a natural extension of the studies described here.Materials and methods Development of the alternative splicing database MouSDB3 For this analysis, we constructed a database of alternatively spliced mouse transcripts called MouSDB3 [ 12 ], using the methods described in [ 23 ]. Briefly, full-length transcript nucleotide sequences were obtained by an Entrez query on 5 August 2003 from GenBank [ 24 ] with molecule selected as mRNA and limits used to exclude expressed sequence tags (ESTs), sequence-tagged sites (STSs), genome sequence survey (GSS), third-party annotation (TPA), working draft and patents. EST sequences were downloaded on 31 July 2003 from dbEST [ 25 ] by extracting only  Mus musculus  entries. All expressed sequences were mapped to a region of the University of California Santa Cruz (UCSC) February 2003 version mm3 of the mouse genome assembly using BLAT [ 26 ]. BLAT tools gfServer and gfClient were installed from jksrc444 dated 15 July 2002 [ 27 ]. This was followed by a careful alignment by SIM4 [ 28 ] version 3/3/2002 to establish splice sites of exons. A post-processing analysis computed genomic exons and determined types of variation for each exon, transcript and locus. Cassette exon analysis We identified in-frame cassette exons and extracted from MouSDB3 nucleotide and amino-acid sequences for transcripts containing these exons. The selected amino-acid sequences were then analyzed with SMART [ 29 , 30 ] to compute protein-domain architecture for each transcript within a cluster. Tissue distribution of alternatively spliced TFs From MouSDB3, we then extracted library information for the transcripts within clusters and their annotations. We used these data to compute the tissue distribution of variant transcripts as reported in Results. All scripts and README files used to carry out this data-gathering process are available upon request from the Laboratory of Computational Genomics of The Rockefeller University.
Materials and methods
Development of the alternative splicing database MouSDB3 For this analysis, we constructed a database of alternatively spliced mouse transcripts called MouSDB3 [ 12 ], using the methods described in [ 23 ]. Briefly, full-length transcript nucleotide sequences were obtained by an Entrez query on 5 August 2003 from GenBank [ 24 ] with molecule selected as mRNA and limits used to exclude expressed sequence tags (ESTs), sequence-tagged sites (STSs), genome sequence survey (GSS), third-party annotation (TPA), working draft and patents. EST sequences were downloaded on 31 July 2003 from dbEST [ 25 ] by extracting only  Mus musculus  entries. All expressed sequences were mapped to a region of the University of California Santa Cruz (UCSC) February 2003 version mm3 of the mouse genome assembly using BLAT [ 26 ]. BLAT tools gfServer and gfClient were installed from jksrc444 dated 15 July 2002 [ 27 ]. This was followed by a careful alignment by SIM4 [ 28 ] version 3/3/2002 to establish splice sites of exons. A post-processing analysis computed genomic exons and determined types of variation for each exon, transcript and locus.
Development of the alternative splicing database MouSDB3
For this analysis, we constructed a database of alternatively spliced mouse transcripts called MouSDB3 [ 12 ], using the methods described in [ 23 ]. Briefly, full-length transcript nucleotide sequences were obtained by an Entrez query on 5 August 2003 from GenBank [ 24 ] with molecule selected as mRNA and limits used to exclude expressed sequence tags (ESTs), sequence-tagged sites (STSs), genome sequence survey (GSS), third-party annotation (TPA), working draft and patents. EST sequences were downloaded on 31 July 2003 from dbEST [ 25 ] by extracting only  Mus musculus  entries. All expressed sequences were mapped to a region of the University of California Santa Cruz (UCSC) February 2003 version mm3 of the mouse genome assembly using BLAT [ 26 ]. BLAT tools gfServer and gfClient were installed from jksrc444 dated 15 July 2002 [ 27 ]. This was followed by a careful alignment by SIM4 [ 28 ] version 3/3/2002 to establish splice sites of exons. A post-processing analysis computed genomic exons and determined types of variation for each exon, transcript and locus.Mus musculusCassette exon analysis We identified in-frame cassette exons and extracted from MouSDB3 nucleotide and amino-acid sequences for transcripts containing these exons. The selected amino-acid sequences were then analyzed with SMART [ 29 , 30 ] to compute protein-domain architecture for each transcript within a cluster.
Cassette exon analysis
We identified in-frame cassette exons and extracted from MouSDB3 nucleotide and amino-acid sequences for transcripts containing these exons. The selected amino-acid sequences were then analyzed with SMART [ 29 , 30 ] to compute protein-domain architecture for each transcript within a cluster.Tissue distribution of alternatively spliced TFs From MouSDB3, we then extracted library information for the transcripts within clusters and their annotations. We used these data to compute the tissue distribution of variant transcripts as reported in Results. All scripts and README files used to carry out this data-gathering process are available upon request from the Laboratory of Computational Genomics of The Rockefeller University.
Tissue distribution of alternatively spliced TFs
From MouSDB3, we then extracted library information for the transcripts within clusters and their annotations. We used these data to compute the tissue distribution of variant transcripts as reported in Results. All scripts and README files used to carry out this data-gathering process are available upon request from the Laboratory of Computational Genomics of The Rockefeller University.


Background Pharmaceutical company representatives (PCRs) influence the prescribing habits and professional behaviour of physicians. However, the skills for interacting with PCRs are not taught in the traditional medical school curriculum. We examined whether an innovative, mandatory workshop for third year medical students had immediate effects on knowledge and attitudes regarding interactions with PCRs.
Background
Pharmaceutical company representatives (PCRs) influence the prescribing habits and professional behaviour of physicians. However, the skills for interacting with PCRs are not taught in the traditional medical school curriculum. We examined whether an innovative, mandatory workshop for third year medical students had immediate effects on knowledge and attitudes regarding interactions with PCRs.Methods Surveys issued before and after the workshop intervention solicited opinions (five point Likert scales) from third year students (n = 75) about the degree of bias in PCR information, the influence of PCRs on prescribing habits, the acceptability of specific gifts, and the educational value of PCR information for both practicing physicians and students. Two faculty members and one PCR led the workshop, which highlighted typical physician-PCR interactions, the use of samples and gifts, the validity and legal boundaries of PCR information, and associated ethical issues. Role plays with the PCR demonstrated appropriate and inappropriate strategies for interacting with PCRs.
Methods
Surveys issued before and after the workshop intervention solicited opinions (five point Likert scales) from third year students (n = 75) about the degree of bias in PCR information, the influence of PCRs on prescribing habits, the acceptability of specific gifts, and the educational value of PCR information for both practicing physicians and students. Two faculty members and one PCR led the workshop, which highlighted typical physician-PCR interactions, the use of samples and gifts, the validity and legal boundaries of PCR information, and associated ethical issues. Role plays with the PCR demonstrated appropriate and inappropriate strategies for interacting with PCRs.Results The majority of third year students (56%, 42/75) had experienced more than three personal conversations with a PCR about a drug product since starting medical school. Five percent (4/75) claimed no previous personal experience with PCRs. Most students (57.3%, 43/75) were not aware of available guidelines regarding PCR interactions. Twenty-eight percent of students (21/75) thought that none of the named activities/gifts (lunch access, free stethoscope, textbooks, educational CD-ROMS, sporting events) should be restricted, while 24.0% (8/75) thought that students should be restricted only from sporting events. The perceived educational value of PCR information to both practicing physicians and students increased after the workshop intervention from 17.7% to 43.2% (chi square, p = .0001), and 22.1% to 40.5% (p = .0007), respectively. Student perceptions of the degree of bias of PCR information decreased from 84.1% to 72.9% (p = .065), but the perceived degree of influence on prescribing increased (44.2% to 62.1% (p = .02)).
Results
The majority of third year students (56%, 42/75) had experienced more than three personal conversations with a PCR about a drug product since starting medical school. Five percent (4/75) claimed no previous personal experience with PCRs. Most students (57.3%, 43/75) were not aware of available guidelines regarding PCR interactions. Twenty-eight percent of students (21/75) thought that none of the named activities/gifts (lunch access, free stethoscope, textbooks, educational CD-ROMS, sporting events) should be restricted, while 24.0% (8/75) thought that students should be restricted only from sporting events. The perceived educational value of PCR information to both practicing physicians and students increased after the workshop intervention from 17.7% to 43.2% (chi square, p = .0001), and 22.1% to 40.5% (p = .0007), respectively. Student perceptions of the degree of bias of PCR information decreased from 84.1% to 72.9% (p = .065), but the perceived degree of influence on prescribing increased (44.2% to 62.1% (p = .02)).Conclusions Students have exposure to PCRs early in their medical training. A single workshop intervention may influence student attitudes toward interactions with PCRs. Students were more likely to acknowledge the educational value of PCR interactions and their impact on prescribing after the workshop intervention.
Conclusions
Students have exposure to PCRs early in their medical training. A single workshop intervention may influence student attitudes toward interactions with PCRs. Students were more likely to acknowledge the educational value of PCR interactions and their impact on prescribing after the workshop intervention.

Background Pharmaceutical company representatives (PCRs) influence the prescribing habits and professional behavior of physicians [ 1 ]. Despite the availability of guidelines regarding appropriate interactions with PCRs for practicing physicians [ 2 - 4 ], the skills for interacting with PCRs have not been included as part of the traditional medical school curriculum. Physicians in training may be particularly susceptible to marketing strategies from PCRs. Restricting interactions between physician in training and PCRs is one approach to eliminating adverse effects of contacts with PCRs [ 5 ]. However, physicians in training will likely deal with such marketing influences once in practice. The provision of training or guided experiences in dealing with PCRs seems a more reasonable educational strategy for producing a physician who will be aware of the potential conflict of interest from the profit motive inherent in the pharmaceutical and other health related industries. To our knowledge, there is only one published study of an educational intervention targeting third year medical students on the subject of appropriate interactions with PCRs [ 6 ]. Furthermore, the best means of developing the skills and attitudes for interacting appropriately with PCRs is not well defined. We sought to examine whether a single workshop intervention had immediate effects on the attitudes of third year medical students regarding interactions with PCRs. The goal of the workshop was to increase the student's knowledge and awareness of ethical issues surrounding the PCR encounter, and to improve the students' interactions with representatives by fostering discussion on the profit motive in pharmaceutical marketing, PCR marketing techniques, and appropriate interactions with the PCR, issues necessary for critical thinking about the potential conflict of interest. Unique to our intervention was the participation of a PCR who role played a typical PCR encounter and who offered a perspective on marketing from the perspective of industry. Our findings have implications for institutions considering strategies for controlling PCR interactions and for medical educators seeking to develop curricula for marketing in medicine.
Background
Pharmaceutical company representatives (PCRs) influence the prescribing habits and professional behavior of physicians [ 1 ]. Despite the availability of guidelines regarding appropriate interactions with PCRs for practicing physicians [ 2 - 4 ], the skills for interacting with PCRs have not been included as part of the traditional medical school curriculum.Physicians in training may be particularly susceptible to marketing strategies from PCRs. Restricting interactions between physician in training and PCRs is one approach to eliminating adverse effects of contacts with PCRs [ 5 ]. However, physicians in training will likely deal with such marketing influences once in practice. The provision of training or guided experiences in dealing with PCRs seems a more reasonable educational strategy for producing a physician who will be aware of the potential conflict of interest from the profit motive inherent in the pharmaceutical and other health related industries. To our knowledge, there is only one published study of an educational intervention targeting third year medical students on the subject of appropriate interactions with PCRs [ 6 ]. Furthermore, the best means of developing the skills and attitudes for interacting appropriately with PCRs is not well defined.We sought to examine whether a single workshop intervention had immediate effects on the attitudes of third year medical students regarding interactions with PCRs. The goal of the workshop was to increase the student's knowledge and awareness of ethical issues surrounding the PCR encounter, and to improve the students' interactions with representatives by fostering discussion on the profit motive in pharmaceutical marketing, PCR marketing techniques, and appropriate interactions with the PCR, issues necessary for critical thinking about the potential conflict of interest. Unique to our intervention was the participation of a PCR who role played a typical PCR encounter and who offered a perspective on marketing from the perspective of industry. Our findings have implications for institutions considering strategies for controlling PCR interactions and for medical educators seeking to develop curricula for marketing in medicine.Methods During the ambulatory internal medicine clerkship of the third year medical school curriculum, students were required to attend a ninety minute workshop entitled "Appropriate Encounters with Pharmaceutical Representatives". These workshops took place three times during the calendar year 2001 for three different student groups. To the best of our knowledge, there were no other organized learning experiences in the medical school curriculum about interactions with pharmaceutical representatives, either before or during the study period. We did not seek approval by the institutional review board for ethical research practice at our institution, because at that time the study was conducted, approval of student education projects was considered unnecessary. Two faculty members interested in the subject (JW, CO), and a regional manager of pharmaceutical representatives from a major pharmaceutical company facilitated the ninety minute workshop. The workshop began by soliciting student opinions regarding the characteristics of typical interactions with PCRs. After a list of characteristics was compiled, each characteristic was discussed in more detail and compared with previous personal experiences with PCRs. Salient points of the subsequent discussion included the usefulness of patient assistance programs, the use of samples and gifts in PCR marketing strategies, the validity and legal boundaries of information provided by the PCR, and the ethical and legal aspects of physician-industry relations. The final segment of the workshop involved two student volunteers who role played a typical PCR encounter in the office. After discussion of the first role play, a second role play between one faculty member (CO) and the PCR demonstrated desirable characteristics of the PCR encounter. A pre-intervention survey handed out and collected prior to the beginning of the workshop solicited information about the number of previous personal experiences with PCRs, and whether the student was previously aware of guidelines (medical school, federal government, or professional society) for appropriate interactions with PCRs. Using five point Likert scales, the survey solicited student attitudes about the educational value of PCR information for practicing physicians and for medical students, the degree of bias in PCR information, and the degree of influence of PCRs on prescribing habits. One additional question solicited the acceptability to students of specific gifts (lunch access, free stethoscope, textbooks, educational CD-ROMS, sporting events) from PCRs. A post-intervention survey with the same attitude questions was administered and collected as students left the workshop. The available data comes from three groups – the third, or last student group of academic year 2000–1 and the first two student groups of academic year 2001–2. Students were characterized by gender, age, and number of previous personal contacts with PCRs (None, 1–3, 4–6, >6). For the purposes of understanding the Likert scale responses for student attitudes, we collapsed Likert scores into three categories – scale responses of 1 or 2 to signify disagreement, a scale response of 3 to signify neutral, and a response of 4 or 5 to signify agreement with the attitude question. We compared student attitudes toward the educational value of PCR detailing for medical students with the perceived value for practicing physicians using the Pearson chi square test. The association between previous personal PCR experience and attitudes about the educational value of PCR detailing was explored using analysis of variance. We also compared attitudes before and after the workshop intervention using the Pearson chi square test and a dichotomous variable a response of 4 or 5 (versus 3 or lower) on the Likert scale.
Methods
During the ambulatory internal medicine clerkship of the third year medical school curriculum, students were required to attend a ninety minute workshop entitled "Appropriate Encounters with Pharmaceutical Representatives". These workshops took place three times during the calendar year 2001 for three different student groups. To the best of our knowledge, there were no other organized learning experiences in the medical school curriculum about interactions with pharmaceutical representatives, either before or during the study period. We did not seek approval by the institutional review board for ethical research practice at our institution, because at that time the study was conducted, approval of student education projects was considered unnecessary.Two faculty members interested in the subject (JW, CO), and a regional manager of pharmaceutical representatives from a major pharmaceutical company facilitated the ninety minute workshop. The workshop began by soliciting student opinions regarding the characteristics of typical interactions with PCRs. After a list of characteristics was compiled, each characteristic was discussed in more detail and compared with previous personal experiences with PCRs. Salient points of the subsequent discussion included the usefulness of patient assistance programs, the use of samples and gifts in PCR marketing strategies, the validity and legal boundaries of information provided by the PCR, and the ethical and legal aspects of physician-industry relations. The final segment of the workshop involved two student volunteers who role played a typical PCR encounter in the office. After discussion of the first role play, a second role play between one faculty member (CO) and the PCR demonstrated desirable characteristics of the PCR encounter.A pre-intervention survey handed out and collected prior to the beginning of the workshop solicited information about the number of previous personal experiences with PCRs, and whether the student was previously aware of guidelines (medical school, federal government, or professional society) for appropriate interactions with PCRs. Using five point Likert scales, the survey solicited student attitudes about the educational value of PCR information for practicing physicians and for medical students, the degree of bias in PCR information, and the degree of influence of PCRs on prescribing habits. One additional question solicited the acceptability to students of specific gifts (lunch access, free stethoscope, textbooks, educational CD-ROMS, sporting events) from PCRs. A post-intervention survey with the same attitude questions was administered and collected as students left the workshop. The available data comes from three groups – the third, or last student group of academic year 2000–1 and the first two student groups of academic year 2001–2.Students were characterized by gender, age, and number of previous personal contacts with PCRs (None, 1–3, 4–6, >6). For the purposes of understanding the Likert scale responses for student attitudes, we collapsed Likert scores into three categories – scale responses of 1 or 2 to signify disagreement, a scale response of 3 to signify neutral, and a response of 4 or 5 to signify agreement with the attitude question. We compared student attitudes toward the educational value of PCR detailing for medical students with the perceived value for practicing physicians using the Pearson chi square test.The association between previous personal PCR experience and attitudes about the educational value of PCR detailing was explored using analysis of variance. We also compared attitudes before and after the workshop intervention using the Pearson chi square test and a dichotomous variable a response of 4 or 5 (versus 3 or lower) on the Likert scale.Results Student characteristics A total of 75 students attended one of the three mandatory workshops on "Appropriate Encounters with PCRs". One student did not complete a post-intervention survey. The mean age of students was 26.4 (± 2.4), and males (56.1%, n = 41) outnumbered females. Fifty-six percent of students (42/75) had experienced more than three personal conversations about a pharmaceutical product with a PCR since starting medical school. Five percent (4/75) claimed no previous personal experience with PCRs. There was no association between the number of PCR contacts, and either gender, age or time of the academic year. Student attitudes toward value of PCR interaction The pre-intervention survey showed that PCR detailing was of educational value to 22.1% (18/75) of students with no perceived difference in educational value to medical students versus that to practicing physicians (chi square, p = .40). While students agreed that the degree of bias from PCR information was substantial (86.7%, 65/75), only 44.0% (33/75) of students felt that pharmaceutical representatives were influential with regard to physicians' prescribing habits. No relationship between number of previous personal PCR contacts and educational value to medical students was demonstrated (ANOVA p = .08) Awareness of guidelines and attitudes toward gifts Forty-three percent (32\75) of students reported awareness of available guidelines regarding PCR interactions. Fifty percent (16/32) of those students reported familiarity with medical school guidelines, 21.8% (7/32) with federal government guidelines, and 40.6% (13/32) with professional society guidelines. When asked which drug company sponsored activities/gifts targeting medical students should be restricted, 28.0% of students (21\75) thought that none of the named activities/gifts (lunch access, free stethoscope, textbooks, educational CD-ROMS, sporting events) should be restricted. Twenty-four percent (8/75) of students thought that only sporting events should be restricted. Effect of workshop intervention on student attitudes Figure  1  shows that the perceived educational value to both practicing and student physicians increased after the workshop intervention from 17.7% to 43.2% (chi square, p = .0001), and 22.1% to 40.5% (p = .0007), respectively. Fifty-eight percent of students (43/74) and 37.8% (28/74), respectively, changed their Likert scale response to the questions on educational value by at least one point after the workshop intervention (Table  1 ). Student perceptions of the degree of bias of PCR information decreased from 84.1% to 72.9% (p = .065), but the perceived degree of influence on prescribing increased (44.2% to 62.1% (p = .02)). The response to the question on the degree of bias in PCR detailing changed by at least one Likert scale point for 17 students (17/74, 23.0%) (Table  1 ). The response to the question on the influence of PCR detailing on prescribing practices changed by at least one Likert scale point for 34 students (34/75, 46.0%). Figure 1 Student attitudes toward PCR detailing before and after workshop intervention . Student perception of the educational value of PCR interactions increased after the intervention at the same time that the perception that PCRs influenced prescribing increased. Student perception of the degree of bias decreased slightly after the workshop, but this decrease was not statistically significant. Table 1 Student attitudes toward PCR detailing before and after workshop intervention In your opinion, what is the educational value to  practicing physicians  offered by detailing from pharmaceutical representatives? (1 = No value at all, 5 = Extremely valuable) Before-Not Valuable (<3) Before-Neutral (3) Before-Valuable (>3) After-Not valuable (<3) 8 1 0 9 After-Neutral (3) 10 20 3 33 After-Valuable(>3) 2 18 12 32 20 39 15 In your opinion, what is the educational value to  medical students  offered by detailing from pharmaceutical representatives? (1 = No value at all, 5 = Extremely valuable) Before-Not Valuable (<3) Before-Neutral (3) Before-Valuable (>3) After-Not valuable (<3) 13 0 0 13 After-Neutral (3) 8 19 4 31 After-Valuable(>3) 6 10 14 30 27 29 18 What is you perception of the degree of bias in the information provided by pharmaceutical representatives detailing to practicing physicians? (1 = Not at all biased, 5 = Totally biased) Before-Not Biased (<3) Before-Neutral (3) Before-Biased (>3) After-Not biased (<3) 0 1 1 2 After-Neutral (3) 0 6 12 18 After-Biased(>3) 0 3 51 54 0 10 64 How influential are pharmaceutical representatives with regard to physicians' prescribing habits? (1 = Not at all influential, 5 = Very influential) Before-Not Influential (<3) Before-Neutral (3) Before-Influential (>3) After-Not influential (<3) 2 2 1 5 After-Neutral (3) 7 11 5 23 After- Influential (>3) 2 17 27 36 11 30 33
Results
Student characteristics A total of 75 students attended one of the three mandatory workshops on "Appropriate Encounters with PCRs". One student did not complete a post-intervention survey. The mean age of students was 26.4 (± 2.4), and males (56.1%, n = 41) outnumbered females. Fifty-six percent of students (42/75) had experienced more than three personal conversations about a pharmaceutical product with a PCR since starting medical school. Five percent (4/75) claimed no previous personal experience with PCRs. There was no association between the number of PCR contacts, and either gender, age or time of the academic year.
Student characteristics
A total of 75 students attended one of the three mandatory workshops on "Appropriate Encounters with PCRs". One student did not complete a post-intervention survey. The mean age of students was 26.4 (± 2.4), and males (56.1%, n = 41) outnumbered females. Fifty-six percent of students (42/75) had experienced more than three personal conversations about a pharmaceutical product with a PCR since starting medical school. Five percent (4/75) claimed no previous personal experience with PCRs. There was no association between the number of PCR contacts, and either gender, age or time of the academic year.Student attitudes toward value of PCR interaction The pre-intervention survey showed that PCR detailing was of educational value to 22.1% (18/75) of students with no perceived difference in educational value to medical students versus that to practicing physicians (chi square, p = .40). While students agreed that the degree of bias from PCR information was substantial (86.7%, 65/75), only 44.0% (33/75) of students felt that pharmaceutical representatives were influential with regard to physicians' prescribing habits. No relationship between number of previous personal PCR contacts and educational value to medical students was demonstrated (ANOVA p = .08)
Student attitudes toward value of PCR interaction
The pre-intervention survey showed that PCR detailing was of educational value to 22.1% (18/75) of students with no perceived difference in educational value to medical students versus that to practicing physicians (chi square, p = .40). While students agreed that the degree of bias from PCR information was substantial (86.7%, 65/75), only 44.0% (33/75) of students felt that pharmaceutical representatives were influential with regard to physicians' prescribing habits. No relationship between number of previous personal PCR contacts and educational value to medical students was demonstrated (ANOVA p = .08)Awareness of guidelines and attitudes toward gifts Forty-three percent (32\75) of students reported awareness of available guidelines regarding PCR interactions. Fifty percent (16/32) of those students reported familiarity with medical school guidelines, 21.8% (7/32) with federal government guidelines, and 40.6% (13/32) with professional society guidelines. When asked which drug company sponsored activities/gifts targeting medical students should be restricted, 28.0% of students (21\75) thought that none of the named activities/gifts (lunch access, free stethoscope, textbooks, educational CD-ROMS, sporting events) should be restricted. Twenty-four percent (8/75) of students thought that only sporting events should be restricted.
Awareness of guidelines and attitudes toward gifts
Forty-three percent (32\75) of students reported awareness of available guidelines regarding PCR interactions. Fifty percent (16/32) of those students reported familiarity with medical school guidelines, 21.8% (7/32) with federal government guidelines, and 40.6% (13/32) with professional society guidelines. When asked which drug company sponsored activities/gifts targeting medical students should be restricted, 28.0% of students (21\75) thought that none of the named activities/gifts (lunch access, free stethoscope, textbooks, educational CD-ROMS, sporting events) should be restricted. Twenty-four percent (8/75) of students thought that only sporting events should be restricted.Effect of workshop intervention on student attitudes Figure  1  shows that the perceived educational value to both practicing and student physicians increased after the workshop intervention from 17.7% to 43.2% (chi square, p = .0001), and 22.1% to 40.5% (p = .0007), respectively. Fifty-eight percent of students (43/74) and 37.8% (28/74), respectively, changed their Likert scale response to the questions on educational value by at least one point after the workshop intervention (Table  1 ). Student perceptions of the degree of bias of PCR information decreased from 84.1% to 72.9% (p = .065), but the perceived degree of influence on prescribing increased (44.2% to 62.1% (p = .02)). The response to the question on the degree of bias in PCR detailing changed by at least one Likert scale point for 17 students (17/74, 23.0%) (Table  1 ). The response to the question on the influence of PCR detailing on prescribing practices changed by at least one Likert scale point for 34 students (34/75, 46.0%). Figure 1 Student attitudes toward PCR detailing before and after workshop intervention . Student perception of the educational value of PCR interactions increased after the intervention at the same time that the perception that PCRs influenced prescribing increased. Student perception of the degree of bias decreased slightly after the workshop, but this decrease was not statistically significant. Table 1 Student attitudes toward PCR detailing before and after workshop intervention In your opinion, what is the educational value to  practicing physicians  offered by detailing from pharmaceutical representatives? (1 = No value at all, 5 = Extremely valuable) Before-Not Valuable (<3) Before-Neutral (3) Before-Valuable (>3) After-Not valuable (<3) 8 1 0 9 After-Neutral (3) 10 20 3 33 After-Valuable(>3) 2 18 12 32 20 39 15 In your opinion, what is the educational value to  medical students  offered by detailing from pharmaceutical representatives? (1 = No value at all, 5 = Extremely valuable) Before-Not Valuable (<3) Before-Neutral (3) Before-Valuable (>3) After-Not valuable (<3) 13 0 0 13 After-Neutral (3) 8 19 4 31 After-Valuable(>3) 6 10 14 30 27 29 18 What is you perception of the degree of bias in the information provided by pharmaceutical representatives detailing to practicing physicians? (1 = Not at all biased, 5 = Totally biased) Before-Not Biased (<3) Before-Neutral (3) Before-Biased (>3) After-Not biased (<3) 0 1 1 2 After-Neutral (3) 0 6 12 18 After-Biased(>3) 0 3 51 54 0 10 64 How influential are pharmaceutical representatives with regard to physicians' prescribing habits? (1 = Not at all influential, 5 = Very influential) Before-Not Influential (<3) Before-Neutral (3) Before-Influential (>3) After-Not influential (<3) 2 2 1 5 After-Neutral (3) 7 11 5 23 After- Influential (>3) 2 17 27 36 11 30 33
Effect of workshop intervention on student attitudes
Figure  1  shows that the perceived educational value to both practicing and student physicians increased after the workshop intervention from 17.7% to 43.2% (chi square, p = .0001), and 22.1% to 40.5% (p = .0007), respectively. Fifty-eight percent of students (43/74) and 37.8% (28/74), respectively, changed their Likert scale response to the questions on educational value by at least one point after the workshop intervention (Table  1 ). Student perceptions of the degree of bias of PCR information decreased from 84.1% to 72.9% (p = .065), but the perceived degree of influence on prescribing increased (44.2% to 62.1% (p = .02)). The response to the question on the degree of bias in PCR detailing changed by at least one Likert scale point for 17 students (17/74, 23.0%) (Table  1 ). The response to the question on the influence of PCR detailing on prescribing practices changed by at least one Likert scale point for 34 students (34/75, 46.0%).Student attitudes toward PCR detailing before and after workshop interventionAfter-Not influential (<3)Discussion Professional relationships with PCRs begin early in a physician's career. Because physicians typically underestimate the influence of pharmaceutical marketing on prescribing practices, countering this naivete early is warranted. Because students do not yet have prescribing privileges, the effect of PCR detailing on the prescribing decision is less relevant than how PCR contact shapes professional values [ 1 ]. Several studies have examined perceptions of the potential influence of PCRs on resident and practicing physicians [ 7 - 13 ]. However, fewer studies have examined the views of medical students [ 6 , 14 , 15 ]. Our data show that students have early exposure to PCRs, perhaps earlier than previously suspected. Only five percent of third year students at this institution had not yet experienced PCR detailing, and many had experienced greater than six such encounters. Although resident physicians understandably have more PCR contacts, on average at least three PCR encounters per month [ 11 , 16 ], to our knowledge, there are no studies of comparable data for medical students. In this study few students were aware of existing guidelines for PCR interactions. Furthermore, students perceived information from PCRs to have educational value, and a value equivalent to that for practicing physicians. That students felt no more or less susceptible to marketing influence than practicing physicians is a marked contrast to the opinions of many educators that physicians in training need special protection from marketing influences [ 1 , 2 , 17 ]. Several interventions have been proposed for educating physicians-in-training about pharmaceutical marketing practices. Shaughnessy et al described a single brief seminar of marketing concepts followed by regular structured evaluation of PCR sales presentations throughout the following year [ 18 ]. Despite this well organized effort, meaningful educational outcomes were meager for the twelve residents evaluated. Hopper et al showed that a single elective forty minute lecture/discussion on ethical and marketing issues in pharmaceutical promotion was successful in improving attitudes and knowledge among residents and faculty [ 19 ]. They presented six vignettes to illustrate marketing techniques related to gifts, guidelines, and the yield of marketing for pharmaceutical companies. Vinson et al showed that a fifty minute lecture for first and second year medical students could have immediate effects on knowledge as measured by repeat anonymous survey six weeks later [ 15 ]. Palmisano et al described a ninety minute lecture and role-play with simulated PCRs to teach analysis of advertising copy and sales techniques, although no data on educational outcomes were offered [ 20 ]. Most similar to our intervention was this study by Wilkes and Hoffman who used pharmacists who were trained to portray PCRs during a one hour seminar targeting third year medical students [ 6 ]. Designed to promote critical thinking about appropriate physician-PCR interactions, the single workshop was successful in increasing the amount of uncertainty students felt about the accuracy and ethics of standard drug "detailing". Similar to these interventions, our workshop intervention targeting third year medical students was a one time intervention and brief in duration. Our intervention differed in that the workshop (1) took place during the clinical clerkship year, (2) made use of practicing PCRs and physicians, and (3) encouraged a distanced but amicable relationship with the PCR. In contrast to many educators who oppose PCR contact for trainees, we encouraged respect for the individual PCR and the success of the pharmaceutical company's business model. We were concerned enough about the growing influence of pharmaceutical marketing on trainees to stage this workshop, but we were careful to remember our goals of encouraging critical thinking about the topic rather than simply condemning the PCR contact. As an example, we emphasized the legal limits regarding what the PCR could and could not say to the physician. This may explain, in part, why attitudes toward PCR information improved after the intervention, at the same time that perceived degree of influence on prescribing increased. Teaching students the "rules of the game" in PCR encounters may explain why students thought that PCR information had more educational value after the workshop. The limitations of this study should be recognized. First, our survey took place at a single academic medical center affiliated with a private hospital. Student attitudes might be different at a state supported institution or at institutions where there are restrictions on the activities of PCRs. Second, students may have answered the post-intervention survey in a socially desirable manner. Respect for the PCR and the business model was presented as a balanced perspective toward marketing in medicine. Third, how immediate changes in student perceptions will ultimately translate into durable attitude changes and prescribing practices was not a goal of this study. We are not naïve enough to be certain that a one time intervention on any subject matter related to ethical issues will change student attitudes in a way that is durable. However, our goal as educators should be to make the students think critically, and demonstrating self-reported attitude changes is a necessary first step toward more durable change. Some academic institutions have chosen to ban PCRs from the academic learning environment. McCormick et al showed that restricting access to PCRs during residency training was associated with less informational dependence on the PCR and a decreased frequency of PCR contact after training [ 5 ]. Underlying such a restrictive policy is the idea that trainees are not able and/or educable to resist the marketing tactics of PCRs. In contrast, our approach is based on the opinion that learning the skills for interacting appropriately with PCRs should not be delayed until a physician has entered practice, and that banning PCRs may simply extend the period of naivete for physicians in training [ 14 ]. Not only does such an omission in the curriculum miss the opportunity to teach physicians about professional relationships surrounding the business model. It also ignores the cost containment needs of the academic medical center and prospective employers. The challenge for medical educators is how to incorporate this increasingly important knowledge domain into training programs. What aspects of marketing strategy need to be taught and how? The growing emphasis on social justice and professionalism should encourage the appropriate distance from and respect for marketing pressures in medicine and add support for this curricular element in medical education [ 21 ]. Our model suggests the possibility of a partnership between the pharmaceutical industry and educators in better preparing phsyicians in training for marketing in medicine. While pharmaceutical companies are the current target of criticism of commercialism in medicine, other services (durable medical equipment, herbal/nutritional supplements, new medical technologies) are all accompanied by marketing pressures that physicians will have to factor into clinical decision making.
Discussion
Professional relationships with PCRs begin early in a physician's career. Because physicians typically underestimate the influence of pharmaceutical marketing on prescribing practices, countering this naivete early is warranted. Because students do not yet have prescribing privileges, the effect of PCR detailing on the prescribing decision is less relevant than how PCR contact shapes professional values [ 1 ]. Several studies have examined perceptions of the potential influence of PCRs on resident and practicing physicians [ 7 - 13 ]. However, fewer studies have examined the views of medical students [ 6 , 14 , 15 ].Our data show that students have early exposure to PCRs, perhaps earlier than previously suspected. Only five percent of third year students at this institution had not yet experienced PCR detailing, and many had experienced greater than six such encounters. Although resident physicians understandably have more PCR contacts, on average at least three PCR encounters per month [ 11 , 16 ], to our knowledge, there are no studies of comparable data for medical students.In this study few students were aware of existing guidelines for PCR interactions. Furthermore, students perceived information from PCRs to have educational value, and a value equivalent to that for practicing physicians. That students felt no more or less susceptible to marketing influence than practicing physicians is a marked contrast to the opinions of many educators that physicians in training need special protection from marketing influences [ 1 , 2 , 17 ].Several interventions have been proposed for educating physicians-in-training about pharmaceutical marketing practices. Shaughnessy et al described a single brief seminar of marketing concepts followed by regular structured evaluation of PCR sales presentations throughout the following year [ 18 ]. Despite this well organized effort, meaningful educational outcomes were meager for the twelve residents evaluated. Hopper et al showed that a single elective forty minute lecture/discussion on ethical and marketing issues in pharmaceutical promotion was successful in improving attitudes and knowledge among residents and faculty [ 19 ]. They presented six vignettes to illustrate marketing techniques related to gifts, guidelines, and the yield of marketing for pharmaceutical companies. Vinson et al showed that a fifty minute lecture for first and second year medical students could have immediate effects on knowledge as measured by repeat anonymous survey six weeks later [ 15 ]. Palmisano et al described a ninety minute lecture and role-play with simulated PCRs to teach analysis of advertising copy and sales techniques, although no data on educational outcomes were offered [ 20 ]. Most similar to our intervention was this study by Wilkes and Hoffman who used pharmacists who were trained to portray PCRs during a one hour seminar targeting third year medical students [ 6 ]. Designed to promote critical thinking about appropriate physician-PCR interactions, the single workshop was successful in increasing the amount of uncertainty students felt about the accuracy and ethics of standard drug "detailing".Similar to these interventions, our workshop intervention targeting third year medical students was a one time intervention and brief in duration. Our intervention differed in that the workshop (1) took place during the clinical clerkship year, (2) made use of practicing PCRs and physicians, and (3) encouraged a distanced but amicable relationship with the PCR. In contrast to many educators who oppose PCR contact for trainees, we encouraged respect for the individual PCR and the success of the pharmaceutical company's business model. We were concerned enough about the growing influence of pharmaceutical marketing on trainees to stage this workshop, but we were careful to remember our goals of encouraging critical thinking about the topic rather than simply condemning the PCR contact. As an example, we emphasized the legal limits regarding what the PCR could and could not say to the physician. This may explain, in part, why attitudes toward PCR information improved after the intervention, at the same time that perceived degree of influence on prescribing increased. Teaching students the "rules of the game" in PCR encounters may explain why students thought that PCR information had more educational value after the workshop.The limitations of this study should be recognized. First, our survey took place at a single academic medical center affiliated with a private hospital. Student attitudes might be different at a state supported institution or at institutions where there are restrictions on the activities of PCRs. Second, students may have answered the post-intervention survey in a socially desirable manner. Respect for the PCR and the business model was presented as a balanced perspective toward marketing in medicine. Third, how immediate changes in student perceptions will ultimately translate into durable attitude changes and prescribing practices was not a goal of this study. We are not naïve enough to be certain that a one time intervention on any subject matter related to ethical issues will change student attitudes in a way that is durable. However, our goal as educators should be to make the students think critically, and demonstrating self-reported attitude changes is a necessary first step toward more durable change.Some academic institutions have chosen to ban PCRs from the academic learning environment. McCormick et al showed that restricting access to PCRs during residency training was associated with less informational dependence on the PCR and a decreased frequency of PCR contact after training [ 5 ]. Underlying such a restrictive policy is the idea that trainees are not able and/or educable to resist the marketing tactics of PCRs. In contrast, our approach is based on the opinion that learning the skills for interacting appropriately with PCRs should not be delayed until a physician has entered practice, and that banning PCRs may simply extend the period of naivete for physicians in training [ 14 ]. Not only does such an omission in the curriculum miss the opportunity to teach physicians about professional relationships surrounding the business model. It also ignores the cost containment needs of the academic medical center and prospective employers.The challenge for medical educators is how to incorporate this increasingly important knowledge domain into training programs. What aspects of marketing strategy need to be taught and how? The growing emphasis on social justice and professionalism should encourage the appropriate distance from and respect for marketing pressures in medicine and add support for this curricular element in medical education [ 21 ]. Our model suggests the possibility of a partnership between the pharmaceutical industry and educators in better preparing phsyicians in training for marketing in medicine. While pharmaceutical companies are the current target of criticism of commercialism in medicine, other services (durable medical equipment, herbal/nutritional supplements, new medical technologies) are all accompanied by marketing pressures that physicians will have to factor into clinical decision making.Conclusions Medical students have exposure to PCRs early in their medical education, at least in this setting. Students perceived information from PCRs to have moderate educational value, and a value equivalent to that for practicing physicians. A brief workshop intervention can have a measurable immediate effect on student attitudes.
Conclusions
Medical students have exposure to PCRs early in their medical education, at least in this setting. Students perceived information from PCRs to have moderate educational value, and a value equivalent to that for practicing physicians. A brief workshop intervention can have a measurable immediate effect on student attitudes.List of abbreviations PCR – pharmaceutical company representative
List of abbreviations
PCR – pharmaceutical company representativeCompeting interests The author(s) declare that they have no competing interests.
Competing interests
The author(s) declare that they have no competing interests.Authors' contributions JW conceived of the study, participated in its design and coordination, and drafted the manuscript. CO participated in design and coordination of the study, conducted the intervention, participated in data interpretation, and manuscript revision. Both authors read and approved the final manuscript.
Authors' contributions
JW conceived of the study, participated in its design and coordination, and drafted the manuscript.CO participated in design and coordination of the study, conducted the intervention, participated in data interpretation, and manuscript revision.Both authors read and approved the final manuscript.Pre-publication history The pre-publication history for this paper can be accessed here:
Pre-publication history
The pre-publication history for this paper can be accessed here: