An insulin-like signaling pathway mediated by DAF-2, an insulin receptor homolog, regulates dauer arrest and longevity in C.elegans.
age-1 encodes a phosphatidylinositol 3-kinase homolog, which has been implicated as a direct target of
daf-2 signaling. Mutations in
age-1 are maternal effect and cause animals to constitutively arrest as dauer larvae. However, maternally rescued
age-1 mutants that lack zygotic
age-1 activity exhibit a two-fold increase in adult lifespan.
daf-2/age-1 signaling negatively regulates
daf-16, a Forkhead-related transcription factor.
daf-16 mutants are dauer defective and completely suppress the dauer constitutive and long-lived phenotypes of
age-1 and
daf-2 null mutants. To identify other components of the
daf-2/insulin-like signaling pathway, specifically downstream components activated by
age-1 PI-3 kinase signaling, we screened for recessive suppressors of
age-1(
mg109) dauer arrest.
mg109 has the same phenotype as a nonsense allele; however, the point mutation it carries results in a complete, albeit mutated, protein. We screened 23,000 genomes and isolated 14 recessive suppressors of
age-1(
mg109). Of these 14
age-1(
mg109) suppressors, 8 have been roughly mapped. Four of these mutations lie on LGV, while the remaining four mutations map to LGIII. Interestingly, one of the mutations on LGV suppresses both the dauer constitutive and the long-lived phenotypes of
age-1(
mg109). The remaining three mutations rescue only the dauer arrest phenotype of
age-1(
mg109). All four of the LGIII-linked mutations are allelic and fail to suppress the long-lived phenotype of
age-1. Of these mutations, one has been further characterized and exhibits no obvious phenotype on its own. Experiments underway include complementation studies, finer mapping, and epistasis analysis.