Worm Breeder's Gazette 10(3): 59
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
lin-3 is a gene necessary for the Vulval Precursor Cells (VPCs; a.k. a. P(3-8).p) to form the vulva in response to a graded inductive signal from the anchor cell. In hermaphrodites carrying Vulvaless ( Vul) alleles of lin-3, induction of the VPCs is lowered or absent such that the vulva can not form and the animal is unable to lay eggs. We are interested in lin-3 because epistasis tests between Vulvaless and Multivulva mutations affecting vulval development indicate that lin-3 acts early in the pathway of vulval development. In addition, other alleles of lin-3 have lethal and sterile phenotypes, indicating that lin-3 has functions other than vulval induction. A F1 screen for new lin-3 alleles was carried out to determine its null phenotype. lin-3(e1417); 90) males were mated to EMS-mutagenized unc-24(e138) 38) dpy-20(e1282) hermaphrodites and the F1 cross progeny were screened for egg-laying defective worms. Since e1417/Df is viable, null alleles could be recovered in this screen. Three early larval lethal alleles (sy51, sy52, sy53) of lin-3 were found among 10,000 F1 progeny. A similar F1 screen by Chip Ferguson ( Genetics 110:17-72 1985) of 20,000 e1417/? F1 generated the lethal allele n1059 and the sterile/larval lethal allele n1058. Because larval lethal alleles are recovered more commonly than Vulvaless alleles in these screens, we believe that larval lethality is the null phenotype. Denise Clark et al. at Simon Fraser, in their analysis of lethals on LG IV, identified two late larval mutations, s751 and s1263, allelic to lin-3. In agreement with the hypothesis that the null phenotype of lin-3 is early larval lethal, they showed that the phenotype of s751/Df and s1263/Df is also early larval lethal ( Genetics 119: 345-353 1988). We are pursuing two approaches to clone lin-3. Our first approach is to generate transposon-induced alleles of lin-3. So far, one putative Tc-induced allele, sy91, was detected by mating lin-3(e1417); 90) males to RW7096 [mut-6 lin-3(+) 192::Tc1) ] hermaphrodites and picking nonUnc egg- laying defective F1. In contrast to the alleles found in the EMS F1 screens, this allele confers a Vul phenotype. sy91 is currently being backcrossed to see if a new Tc band can be correlated with the Vul phenotype. Our second approach is to map lin-3 with respect to cloned DNA in an attempt to define a region of DNA that must contain lin-3. We have been mapping lin-3 to sP5, an RFLP on the right end of the contig L122, to determine whether L122 extends far enough to cover lin- 3. 22 Vul nonDpy recombinants were picked from lin-3(e1417) 362) /BO heterozygotes. All the recombinants possessed the N2 version of sP5. Therefore sP5 is probably to the left of, or close and to the right of, lin-3. We are currently examining recombinants in the mec-3 to lin-3 interval to determine the map order.