Control of cell fate in the tail region of C. elegans by the gene egl-5.

The tail region of C. elegans contains a number of blast cell and neuron types that either are found only in the tail, or are different from more anterior homologues. In egl-5 mutants, the fates of many of these tail cells are abnormal or transformed to those of anterior homologues. The affected cells are related only by position and not by ancestry. egl-5 is also required for normal development of the somatic gonad and sex muscles in males. The function of egl-5 in all these tissues is cell autonomous. By genetic mapping, egl-5 lies very close to mab-5, a gene with an analogous role in the immediately anterior body region. egl-5 and mab-5 may constitute a 'mini-cluster' of regional determination genes, similar to those described in other animal phyla.