wnt homologs in Caenorhabditis elegans Supriya Shivakumar, Gregg Jongeward, Cynthia Kenyon and Harold Varmus. University of California, San Francisco, CA 94143 The wnt gene family encodes cysteine-rich secreted proteins which have been shown to act as important regulators of early development in the frog, fly and mouse. wnt genes have a crucial role in intercellular signaling in the mouse CNS development and in pattern formation in the fly. We chose to study the normal role of Ce-wnt-Z in signaling in C. elegans development. Two members of the wnt gene family have been identified in C elegans, Cc-wnt 1 and
Ce-wnt-22. The
Ce-wnt-1 gene encodes a 372 amino acid protein and shares 22 of the 24 cysteines found among other members of the wnt family. A 1.4 kb transcript (including an SL1 transpliced leader sequence) is detected at high levels in embryos and at lower levels at all other stages. The 1.4 kb
Ce-wnt-2 cDNA is also expressed in a similar temporal pattern to
Ce-wnt-1. The
Cc-wnt-2 cDNA encodes a protein of 362 amino acids with 22 of the cysteines shared among other Wnt proteins. Neither Ce-wnt 1 and
Ce-wnt-2 are direct homologs of any specific wnt genes in other organisms. To elucidate the functions of the Ce-wnt-Z gene product, we have isolated mutations in the gene. The Ce- wnt-l locus maps to the left arm of chromosome II, but does not appear to correspond to any existing mutations. We made the assumption that the
Ce-wnt-1 gene is required for viability based on wnt mutant phenotypes in other species. We screened for psoralen induced lethal mutations balanced by an extrachromosomal array comprising a 15 kb lambda clone containing the
Ce-wnt-1 gene and a marker (
rol-6D) in a F2 clonal screen (see diagram below). 1500 F2 animals were screened and 2 embryonic lethal alleles were isolated. Both contain deletions in the Ce
wnt-1 coding region. These mutations are rescued by the lambda done, but not by
rol-6. A 53 kb subdone also rescues the lethality. We are now trying to demonstrate conclusively that this early embryonic lethality is due to the disruption of the
Ce-wnt-1 gene. We have also screened for psoralen induced mutations (in an identical screen) that require a cosmid clone containing Ce-
wnt-2. We have identified a number of mutations in the screen which we are nDw analyzing in more detail. 1Shackleford et al., Oncogene 8:1857 (1993) 2Waterson et al., Nature genetics 1:114 (1992)