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.

Embryonic Expression of unc-8 Suppressor sup-42.

Wayne Shreffler, Eve Wolinsky

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).