We are interested in studying various steps of vulval fate specification and morphogenesis. Here we report our analyses on four vulval defective mutants.
ku229 was identified in a temperature-sensitive (TS) mutant screen for mutants involved in vulval morphogenesis, although the mutation itself is not TS. About 60% of
ku229 worms are Egl. Under Nomarski optics, many
ku229 worms have abnormal but recognizable "Christmas-tree" structures, and seem to have numerous lineage defects. A weak
lin-39 allele,
n709ts, can enhance the Egl phenotype of
ku229 to 95%. These results suggest that the gene defined by
ku229 may be involved in vulval cell fate specification. When
ku229 is placed over a deficiency, the Egl phenotype is significantly weaker (~20%), suggesting that
ku229 could be a gain-of-function allele. We have mapped
ku229 to a small region on LGIV and have been using several methods to clone the gene. Our laboratory has been screening and analyzing many sterile mutants with protruding vulvae (Pvl) in the past a few years. The studies have also included many evl genes identified previous by G. Seydoux in I. Greenwald's lab (1), three of which are described here. First,
evl-14 seems to have a lineage defect and dose not form a wild-type Christmas-tree structure.
evl-4 is defined by a mutation that displays a Cog (connection to gonad defective) phenotype.
evl-22 mutants have an abnormal vulval lineage so the vulva usually consists of less than 15 nuclei instead of 22 in wild type.
evl-22 mutants also show underproliferation in somatic gonad and germ line suggesting that the gene plays a role in cell division in general. After further mapping, we have rescued all three genes either with a single cosmid/fosmid clone or, in the case of
evl-22, with two overlapping cosmids. We are in the process of determining the specific open reading frames for these genes. (1)Seydoux, G, Savage, C., and Greenwald I. (1993). Developmental Biology 157, 423-436.