Our lab is studying the molecular mechanisms of nervous system development. Mutants bearing the canonical
unc-20 allele,
e112, display a temperature-sensitive coiling phenotype. Phil Anderson's laboratory has identified six alleles of
unc-20 that cause a phenotype similar to
unc-20 (
e112) when heterozygous in a
smg-1 mutant background. These alleles cause a homozygous L1 lethal phenotype, suggesting that
unc-20 provides an essential function.
unc-20 (
e112) and
unc-20 (
r990)/+;
smg-1 (
r861) strains display defects in HSN axon pathfinding and extension and AVKR axon pathfinding.
unc-20 (
e112) animals also display defects in VD/DD axon pathfinding (Y. Jin, personal communication), VC axon anatomy, and serotonin sensitivity (T. Rakow and B. Schafer, personal communication). Therefore, we propose that
unc-20 functions in nervous system development and an unknown essential process. In order to understand the role of
unc-20, we embarked on a positional cloning strategy to isolate the gene. Genetic mapping has demonstrated that
unc-20 lies to the right of
imo-1, bwP1, and
gpd-2,3; and to the left of
fax-1. This defines a relatively small region that is covered by cosmids M01F3, C15C7, and W05A4. M01F3 and a subclone containing the left-hand 10kb of C15C7 fail to rescue
unc-20 (
e112), suggesting that
unc-20 may lie in the C15C7 or W05A4 clones. We have not been successful at recovering stable transgene arrays with the entire C15C7 clone. The
gm27 deletion removes
fax-1 and flanking DNA, including most of cosmid W05A4 and the right-hand portion of C15C7. The
gm27 mutation complements
unc-20(
e112) suggesting that
unc-20 lies in the central portion of the C15C7 clone. This region contains four predicted genes. We have attempted RNAi with cDNA clones from two these predicted clones, and have not obtained phenotypes consistent with known
unc-20 phenotypes. We are currently amplifying DNA from
unc-20 (
e112) and
unc-20 (
r997) animals to determine if any of the four predicted genes in this region contain mutations in these strains.