Worm Breeder's Gazette 11(3): 26
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.
Mutations in unc-34 and unc-76 cause a number of axons to end prematurely or, less frequently, to follow aberrant paths. Affected neurons include the serotoninergic HSN motor neurons (1), the GABAergic VD and DD motor neurons (2), and sensory neurons in the amphids and phasmids (3). The Unc phenotype of unc-76 animals is more severe than that of unc-34 animals, but all of the neurons listed above show qualitatively similar defects in the two mutants. To identify genes with products that interact with the unc-76 product in neuronal guidance, we have screened approximately 100,000 haploid genomes for suppressors of the unc-76(e911) e. We isolated only ten weakly-suppressed strains, and in each of the five strains analyzed, the suppressor appears to be a smg suppressor (conferring a protruding-vulva phenotype and capable of suppressing lin-29(n546)). Furthermore, smg- 1(e1228) suppresses unc-76(e911) to roughly the same extent as the suppressors isolated in the screen. The smg-suppressibility of unc-76( e911) suggests that this allele reduces the amount of unc-76 RNA but does not eliminate it. Mapping of DNA polymorphisms near dpy-29 by Bob Klein in Barbara Meyer's laboratory suggested that unc-76 (which lies 0.1 map units to the right of dpy-29) was likely to be included in the par-1 contig. We found that a mixture of the cosmids C25D7, C56C4, and C08C1 together with pRF4 (rol-6(d)) can rescue the Unc phenotype of unc-76( e911). Single-cosmid injection experiments showed that C56C4, C13G10, and C08C1 all can rescue unc-76, while C25D7 cannot. These observations define a region of about 27 kb that contains the unc-76 gene. We are testing subclones of these cosmids for rescuing activity. The unc-34 gene is likely to be contained in the TCUNC60C contig Analysis of recombinants in the unc-34-to-unc-60 interval (1.7 map units) has shown that N2-EM1002 polymorphisms identified by cosmids F59C5 and R09A1 map to the right of unc-34 (by 0.9 and 0.2 map units, respectively). A polymorphism identified by cosmid K08B11 has not been separated from unc-34 (0/23 unc-34-non-unc-60 recombinants), indicating that it lies to the left of unc-34 or within 0.07 map units on the right. R09A1 and K08B11 are joined by three YACs, but no cosmids have been identified between them. A rough estimate of physical map distance in the region based on the above three-factor mapping and the computer drawn physical map suggests that a distance of 0.1 map units corresponds to about 50 kb. This estimate places the unc-34 gene within a cosmid length of K08B11 on the left or in the YAC region between R09A1 and K08B11. We are attempting to rescue unc-34 with cosmids in this region and will obtain subclones of the appropriate YACs if necessary.