Worm Breeder's Gazette 13(5): 38 (February 1, 1995)
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.
Dept. Biochemistry, NYU Medical School, *0 First Ave., NY 10012
Strong unc-8 (IV) dominant mutations produce ventral motorneuron swelling, coiling, and inability to back. These phenotypes are suppressed by mec-6 mutations (WBG13(3):77, Genetics, in press), suggesting afunctional similarity to members of the deg-1 ion channel family. The strong unc-8 phenotype allows ready isolation of suppressor mutations that restore the ability to move backwards. One such mutation, sup-42(lb88) X, obtained after EMS mutagenesis of unc-8(n491), recessively restores backing ability and largely suppresses the motorneuron swelling phenotypes of unc-8 strong dominant mutations, although it does not restore fully wild-type locomotion. Cultures of unc-8(n491); sup-42(lb88) double mutants also grow surprisingly slowly despite this amelioration of the Unc-8 phenotype. sup-42(lb88) in the absence of other mutations confers an extremely mild sluggish Unc phenotype. The slow growth of the double mutant, may, however, be explained by embryonic lethality of sup-42(lb88). 25 percent of sup-42(lb88) eggs and 44percent of unc-8(n491);sup 42(lb88) eggs fail to hatch, as compared to 1percent of wild-type strain N2 and 8percent of unc-8(n491) single mutant eggs. At least 10percentof both early and late sup 42(lb88) and unc-8(n491);sup-42(lb88) embryos contain large swollen cells. These embryonic swellings could be due to an osmotic defect or reflect secondary leakiness of cells dying from other causes. Larval lethality is comparable to wild-type; with the exception of unusual sickly newly-hatched animals, cell swel!ing is not observed in larvae or adults. Thus, sup-42 appears to function during embryogenesis, as well as interacting with unc-8 in the nervous system after hatching. sup-42(lb88) suppression of unc-8(n491) in a mec-6(+) background argues against functional redundancy with mec-6. sup-42 might be a functional homolog of the deg-1 family, in which case suppression of sup-42(lb88) embryonic lethality by mec-6 is predicted. Interactions of sup-42 with other deg-1 family members and unc-8 suppressor mutations are being tested. Perhaps sup-42(lb88) will prove to identify a novel channel regulator. In order to clone unc-8 and its hypodermally-active suppressor gene sup 40 (I), we have been injecting nearby cosmids. Both genes are identified by dominant mutations with deleterious effects, therefore a multi-copy array of wild type DNA may be harmful. It has proven, in fact, extremely difficult to obtain any transformants (as marked by coinjected antisense Roller plasmid), and no stably transmitting arrays have yet been obtained from either the LGI or LGIV cosmids injected as a group. We are currently trying to identify an individual "killer" cosmid from each group (which may, however, encode a harmful sequence unrelated to sup-40 or unc-8).