Worm Breeder's Gazette 11(5): 31
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
The genes unc-34 and unc-76 are required for normal outgrowth of many neuronal processes. Mutations in either gene cause several classes of neurons to terminate outgrowth prematurely (HSN motor neurons (1), PHA, PHB, PDE, and amphidial sensory neurons (2)) or to follow abnormal paths (VD and DD motor neurons (3), AVM mechanoreceptors (4)). Our studies have led us to believe that these genes function generally in axonal guidance and organization of axon bundles. We previously reported that several cosmids rescue the unc-76 e in germline transformation experiments (WBG 11(3): 26). Two rescuing cosmids, C56C4 and C08C1, have 27 kb in common. A 15 kb subclone from this region of C56C4 gives full rescuing activity, and smaller subclones of 8.5, 7.0, 6.2, and 5.5 kb rescue the Unc phenotype of young larvae but give weaker rescue in older animals. We screened 220,000 plaques from Stuart Kim's mixed-stage cDNA library using the 8.5 kb subclone as a probe and identified five cDNA clones. Two of these clones, 1.8 and 2.4 kb in size, hybridize to the 5.5 kb rescuing region. Both of these clones hybridize to a 1.8 kb RNA band in Northern blots of embryonic poly-A(+) RNA. We believe that this RNA represents the unc-76 transcript because the amount of this RNA in unc-76(e911) embryos is much lower than that in N2 embryos. unc-76(e911) is weakly suppressed by smg suppressors, which have been shown to elevate the level of message in certain unc-54 mutants in which the amount of message is reduced (5). However, the amount of the 1.8 kb message in smg-1(e1228) him-2(e1065); 11) embryos is only slightly higher than that in unc-76(e911) embryos. Sequence analysis of the 1.8 kb cDNA identified a single long open reading frame that could encode a 379-amino acid polypeptide. A search of the Genbank database using the FASTA program revealed no significant similarities to known proteins. Neither cDNA clone appears to contain the 5' end of the gene, but the 2.4 kb cDNA clone includes an additional 130 bp at the 5' end of the open reading frame, extending it to 422 amino acids. Comparison of the restriction maps of the two cDNA clones suggests that the 2.4 kb clone contains about 0. 5 kb of DNA 3' to the sequences contained in the 1.8 kb cDNA, but we do not yet know whether this 0.5 kb of additional DNA represents a cloning artifact or an alternative splicing product with additional 3' exons.