cGMP dependent protein kinases (PKGs) are key signaling molecules, yet their down stream signaling pathway(s) including their substrates remain poorly understood. I am using a genetic approach in worms to understand PKG signaling. Gain of function activity of the
egl-4 gene, which encodes a worm PKG, results in a small body size, reduced intestinal darkness, increased intestinal nile red staining, reduced longevity, and sleep-like behavior during the adult stage. Loss of
egl-4 function results in the opposite of these phenotypes as well as in sensory adaptation defects, Aldicarb resistance, and increased propensity to form dauers. Based on analysis of animals that are doubly mutant for known signaling pathway components and either an
egl-4(gf) mutant or an
egl-4(lf) mutant, the signaling pathways involved in some of these phenotypes have been identified. DAF-7 TGF-? signaling functions down stream of
egl-4 in the control of intestinal darkness, DBL-1 TGF-? signaling functions down stream in the control the body size, insulin signaling is down stream in the control of longevity, and a cGMP-dependent cation channel is involved in the sensory adaptation pathway (Daniels et al ''00; Fujiwara et al 02, Hirose et al 04, lEtoile et al 02, Raizen et al, ‘06). To further our understanding of the PKG signaling pathway(s), I searched for mutants that suppressed the
egl-4(gf) mutant
ad450sd. I am particularly interested in those mutants that suppress most to all of the gf phenotypes since the genes affected in these mutants may act more proximally in
egl-4 signaling pathways. I screened the progeny of ~6000 chemically mutagenized
ad450 F1s for worms that appeared darker, more active, and/or larger than
ad450 worms. The largest class of suppressors consists of loss of function mutations in
egl-4, which occurred at a rate of approximately 1/1000 haploid genomes. A second class consists of 3 mutants that suppress the pale intestine phenotype but not other phenotypes of
egl-4(gf). Other phenotypes of these suppressors suggest that they are likely to encode genes that function in the
daf-7 TGF-? signaling pathway. Indeed, based on mapping, complementation, and sequencing, one of these,
cs82, encodes a mutation in
daf-8. A third class consists of 3 mutants that partially suppress more than one
egl-4(gf) phenotypes, and do not map to the
egl-4 locus. The genes affected in these mutants may function generally in PKG signaling. I am currently characterizing these mutants.