AN ANKYRIN-RELATED GENE (UNC-44) IS NECESSARY FOR PROPER AXONAL GUIDANCE IN CAENORHABDITIS-ELEGANS

Caenorhabditis elegans unc-44 mutations result in aberrant axon guidan ce and fasciculation with inappropriate partners. The unc-44 gene was cloned by transposon tagging, and verified by genetic and molecular an alyses of six transposon-induced alleles and their revertants. Nucleot ide sequence analyses demonstrated that unc-44 encodes a series of put ative ankyrin-related proteins, including AO49 ankyrin (1815 aa, 198.8 kD), AO66 ankyrin (1867 aa, 204 kD), and AO13 ankyrin (less than or e qual to 4700 aa, less than or equal to 517 kD). In addition to the maj or set of similar to 6 kb alternatively spliced transcripts, minor tra nscripts were observed at similar to 3, 5, 7, and 14 kb. Evidence is p rovided that mutations in the similar to 14-kb AO13 ankyrin transcript are responsible for the neuronal defects. These molecular studies pro vide the first evidence that ankyrin-related molecules are required fo r axonal guidance.