2000 East Coast Worm Meeting abstract 69
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Yale University
Neurotransmitters can mediate neural communication by activating heterotrimeric G proteins that signal through poorly understood pathways. GOA-1, a G protein expressed in the C. elegans nervous system, is 80% identical to human Goa, the major G protein of the brain. Neural signaling defects in goa-1 mutants result in hyperactivity of several behaviors, including feeding, locomotion, and egg laying.
To identify components of the GOA-1 signaling pathway, we screened 39,000 mutagenized haploid genomes for mutations that confer a phenotype similar to that of goa-1 loss-of-function mutants. Like goa-1, these hyperactive egg-laying mutants lay their eggs soon after fertilization, presumably due to the hyperstimulation of the egg-laying machinery. This results in worms that accumulate very few eggs within their uterus and eggs that are laid at an early stage of development. In the past, it has been difficult to identify mutants with this phenotype (thin and empty of eggs) because they resemble both young adults and the partially sterile animals that appear at a high frequency following mutagenesis. To overcome this difficulty we developed an efficient selection for the early-stage eggs laid by hyperactive egg-laying mutants that is followed by a visual rescreening for animals resembling goa-1 mutants. This procedure allows for the identification of mutants with neurotransmitter signaling defects due to the altered function of proteins both upstream and downstream of GOA-1.
This screen has isolated mutants with the desired hyperactive egg-laying phenotype. We are currently characterizing 17 isolates that lay greater than 70% of their eggs at the 8-cell stage or earlier. The strength of this phenotype distinguishes these mutants from previously described "Egl-C" mutants which, in a limited survey, typically lay a much lower percentage of early-stage eggs. Only loss-of-function mutations in goa-1 and eat-16, components of G-protein signaling pathways that control egg-laying behavior, have comparably strong phenotypes. Interestingly, all of the mutations analyzed from this screen show some degree of semi-dominance, as do goa-1 (n363) and eat-16(ad702). We plan to clone and characterize the genes identified in this screen to understand GOA-1 signaling at a molecular level.