HOM-C/Hox genes and four interacting loci determine the morphogenetic properties of single cells in the XXXX male tail.

@entity2199 @entity56607 @entity43307
The copulatory structure of the @entity2199 male tail includes a set of nine bilaterally symmetrical pairs of sense organs known as rays. Each ray comprises three cells, which are generated by a stereotyped cell sublineage expressed by 18 epidermal ray precursor cells. A pattern formation mechanism in the epidermis guides the specification of morphogenetic differences between the rays necessary for correct organelle assembly at specific positions within the epidermis. Expression of these ray differences was altered in mutations we described previously, resulting in displaced and fused rays. Here we show that two genes of the @entity2199 HOM-C/Hox gene complex play a role in the pattern formation mechanism. Increasing or decreasing the gene dosage of @entity43307 , an Antennapedia homolog, and @entity56607 , an Abdominal B homolog, results in displacement and fusion of specific rays. These changes are interpreted as anterior or posterior transformations in ray identities. Mutations in the genes previously described are dominant modifiers of these effects. This suggests that these genes act in the same morphogenetic pathway as @entity43307 and @entity56607 . Several lines of evidence, including cell ablation experiments, argue that the identity of each ray is specified cell-autonomously in the terminal cells of the ray lineages. @entity43307 and @entity56607 , therefore, specify the morphogenetic properties of differentiating cells, without change in cell lineage or apparent cell type. Modifier genes may act upstream of @entity43307 and @entity56607 to regulate their expression. Alternatively, they may act at the same step in the pathway, as cofactors, or they may be target genes. Target genes could include genes specifying cell recognition and adhesion molecules governing ray organelle assembly.
