Deciphering the role of V200A and N291S mutations leading to LPL deficiency.
BACKGROUND AND AIMS
Type I hyperlipoproteinemia is an autosomal recessive disorder of lipoprotein metabolism caused by mutations in the LPL gene, with an estimated prevalence in the general population of 1 in a million. In this work, we studied the molecular mechanism of two known mutations in the LPL gene in ex vivo and in vitro experiments and also the effect of two splice site mutations in ex vivo experiments.


METHODS
Two patients with hypertriglyceridemia were selected from the Lipid Clinic in Vienna. The first patient was compound heterozygote for c.680T > C (exon 5; p.V200A) and c.1139+1G > A (intron 7 splice site). The second patient was compound heterozygote for c.953A > G (exon 6; p.N291S) and c.1019-3C > A (intron 6 splice site). The LPL gene was sequenced and post-heparin plasma samples (ex vivo) were used to test LPL activity. In vitro experiments were performed in HEK 293T/17 cells transiently transfected with wild type or mutant LPL plasmids. Cell lysate and media were used to evaluate LPL production, secretion, activity and dimerization by Western blot analysis and LPL enzymatic assay, respectively.


RESULTS
Our data show that in both patients, LPL activity is absent. V200A is a mutation that alters LPL secretion and activity whereas the N291S mutation affects LPL activity, but both mutations do not affect dimerization. The effect of these mutations in patients is more severe since they have splice site mutations on the other allele.


CONCLUSIONS
We characterized these LPL mutations at the molecular level showing that are pathogenic.
['Botta|Margherita|M|', 'Maurer|Elisabeth|E|', 'Ruscica|Massimiliano|M|', 'Romeo|Stefano|S|', 'Stulnig|Thomas M|TM|', 'Pingitore|Piero|P|']
D000328:Adult D057809:HEK293 Cells D006579:Heterozygote D006801:Humans D008072:Hyperlipoproteinemia Type I D015228:Hypertriglyceridemia D008071:Lipoprotein Lipase D008297:Male D016297:Mutagenesis, Site-Directed D020125:Mutation, Missense D010375:Pedigree D010641:Phenotype D055503:Protein Multimerization D017422:Sequence Analysis, DNA
Familial hypertrygliceridemia Lipase deficiency Lipoprotein lipase Missense and frameshift mutations cs941507 rs268 rs528243561 rs767260655