The Pristionchus pacificus mab-5 gene is involved in the regulation of ventral epidermal cell fates.

One system that can be used to study the evolution of gene function is the nematode vulva. In Caenorhabditis elegans, the vulva is formed from three of the six multipotent precursors P(3-8).p. Comparison of vulval development between C. elegans and Pristionchus pacificus has revealed that, during evolution, there have been changes in the specification of cell fate for certain vulval cells. For example, the cell P8.p is a vulval precursor cell (VPC) in C. elegans, but is incompetent to adopt vulval fate in P. pacificus We have fate specification and have isolated P. pacificus mutants with a second vulva-like structure in the posterior region resulting from the ectopic differentiation of P8.p Genetic and molecular analysis indicated that point mutations in the Hox-cluster gene mab-5 of P. pacificus cause this multivulval phenotype. Further cell ablation studies revealed that the differentiation of P8.p is independent of gonadal signaling. In C. elegans, mab-5 also acts in P8.p specification, but mab-5 mutant animals do not develop differs between species, indicating that alterations in the intrinsic properties of P8.p and corresponding changes in the functional specificity of mab-5 have occurred during evolution.