2000 West Coast Worm Meeting abstract 44
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| 1 | Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195 |
| 2 | Department of Genetics, University of Washington, Seattle, WA 98195 |
We have isolated and characterized mutants that are strongly Daf-c at 27° but that are not Daf-c at 25°, a phenotype we call Hid (high temperature-induced dauer formation). Previously identified mutants with this phenotype include unc-64, unc-31, unc-3, egl-4, daf-3 and the dyf mutants. We screened for new Hid mutants at 27° and isolated 100 mutants, including twenty-three alleles of known Daf-c genes (many weak alleles), sixteen alleles of dyf or other Daf-d genes and five alleles of unc-31 or unc-3. We also isolated alleles of a number of new dauer genes. These include alleles of the genes pdk-1, akt-1, aex-6, kin-8 and hid-1.
Many of the Hid mutants are fully suppressed by mutations in daf-16, suggesting that these genes act in the daf-2/age-1 (insulin-receptor /PI3 kinase) pathway. These include unc-64 and unc-31, which encode neurosecretory proteins that may be involved in insulin secretion, and pdk-1and akt-1 which encode PI3-dependent protein kinases that act downstream of age-1. The aex-6 and hid-1 genes may also act in this pathway. In addition to their Hid phenotype, the aex-6 and hid-1 mutants also have defects in movement and defecation, suggesting that they may function in a common process to regulate multiple behaviors. We cloned hid-1 and found that it encodes a novel protein with many transmembrane domains. The HID-1 protein is strongly conserved in Drosophila and humans, with each organism appearing to carry only one gene of this type.
Reexamining the epistatic interactions of strong Daf-c genes at 27° leads to several new inferences. Mutations in the TGF-b pathway Daf-c genes and daf-2 are completely suppressed by daf-5 and daf-16, respectively, at 25° but only partially suppressed at 27°. This suggests that there are additional branches of the TGF-b and insulin pathways that are not detected at 25°. Furthermore, epistasis results based on pheromone response at 25° show qualitative differences from epistasis results at 27°, indicating that gene interactions inferred from epistasis experiments performed under one set of conditions may not be the same as those under a different set of environmental conditions.