SUPPRESSORS OF THE UNC-73 GENE OF CAENORHABDITIS-ELEGANS

The unc-73 gene of Caenorhabditis elegans is necessary for proper axon guidance. Animals mutant in this gene are severely uncoordinated and also exhibit defects in cell migration and cell lineages. We have isol ated coordinated revertants of unc-73(e936). These fall into three cla sses: intragenic revertants, extragenic dominant suppressors (sup-39), and a single apparently intragenic mutation that is a dominant suppre ssor with a linked recessive lethal phenotype. sup-39 mutations cause early embryonic lethality, but escapers have a wild-type movement phen otype as larvae and adults. Gonads of sub-39 mutant animals show a nov el defect: normal gonads have a single row of oocytes, but sup-39 gona ds often have true rows of oocytes. This result suggests that the muta nt gonad is defective in choosing on its surface only a single site fr om which nuclei will emerge to form oocytes. These results are interpr eted in terms of an effect of unc-73 on determination of cell polarity .