GENETIC-REGULATION OF MEC-3 GENE-EXPRESSION IMPLICATED IN THE SPECIFICATION OF THE MECHANOSENSORY NEURON CELL-TYPES IN CAENORHABDITIS-ELEGANS

The mec-3 gene, a member of the LIM-homeodomain transcription factors, is required for touch receptor, FLP and PVD neurons to differentiate in the nematode Caenorhabditis elegans. Stably integrated transgenic strains with mec-3-lacZ fusion were generated by irradiating UV light to an unstable transgenic strain with the extrachromosomal DNA. Expression patterns of the mec-3-lacZ fusion were examined in mutant backgrounds (lin-4, lin-14, egl-44, egl-46 and sem-4 genes) which alter touch receptor-specific gene expression. In the lin-4 mutant background, ectopic mec-3-lacZ positive AVM/PVM-like cells were observed in 9% of the animals. By contrast, in the lin-14 mutant background, mec-3-lacZ staining in AVM/PVM cells was lost in 86% of the animals. In the egl-44 and egl-46 mutant backgrounds, expression pattern was the same as wild-type animals. In the sem-4 mutant background, more than half of the animals (54-69%) had ectopic staining cells in the tail in addition to the wild-type staining pattern. The modes of action of these genetically interacting genes in the differentiation of mechanosensory neurons are proposed.