GLP-1 is a Notch-type receptor that mediates various inductive signals during development. In the adult, it mediates a proliferative signal from the somatic distal tip cells to the germ line. In the absence of GLP-1 signaling, germ cells exit mitosis, enter meiosis, and differentiate. Mutations in
ego-3,
ego-4, and
ego-5 were isolated as recessive enhancers of
glp-1 in the germ line (Qiao et al., 1995). In a
glp-1(+) background,
ego-3,
ego-4, and
ego-5 mutants are sterile, with various defects in germline development. We have mapped them relative to visible genetic markers, but to refine their position in preparation for molecular studies, we have turned to SNP (single nucleotide polymorphism) mapping. ego mutations were induced in an N2 background, therefore we are mapping polymorphic sequences in the so-called "Hawaiian" strain, HA-8 (CB4856). When possible, we use "snip" SNPs that can be detected by restriction digest. Once each ego gene is mapped to a manageable region, we use RNAi to phenocopy predicted genes in the to see whether we can detect either the ego developmental phenotype or enhancement of
glp-1. Conventional mapping places
ego-3 to the left of
unc-61 (on Y50E8) and very close to
daf-21 (on C47E8) on chromosome V. In previous studies, we had attempted without success to identify
ego-3 by transformation rescue using cosmids from this region (L. Qiao and E. Maine, unpublished). As an alternative, we identified SNPs in the area, on C54G10, R08A2, Y50E8, and C48G7. Since genome-wide SNP screens have identified few SNPs here, ours may be useful for other researchers and will be included in a figure on the poster. We isolated a set of recombinants to the left and right of
ego-3, and assayed the appropriate SNPs. This mapping allowed us to further delineate the
ego-3 region. We are now using RNAi to phenocopy genes in the region to see whether we can detect either the
ego-3 developmental phenotype or enhancement of
glp-1.