Worm Breeder's Gazette 13(1): 50 (October 1, 1993)

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.

Further analysis of the C. elegans cofilin gene, unc-60 V.

Erin Gilchrist, Dinar Suleman, David Baillie.

Institute of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5 A1S6.

The unc-60 gene has been cloned and sequenced (McKim, et al ., 1993 , M.G.G., in press), and encodes two products that resemble the mammalian actin-binding family of proteins called cofilins. Mutations in the unc-60 gene result in either paralysis or lethality. Homozygous viable Unc-60 mutants, not surprisingly, exhibit disorganized thin filaments in the body wall muscle cells (Francis and Waterston, 1985, J.C.B. 101: 1532-1549). Animals homozygous for the lethal allele arrest early in larval development but do not exhibit the two-fold phenotype typical of several essential muscle-affecting genes (McKim, et al., 1993).

The two unc-60 gene transcripts, A and B, are generated through alternative splicing, and share only an initial methionine codon. The products of these transcripts are similar to each other and to the mammalian and yeast cofilin proteins. The lethal phenotype of the s1586 allele has been shown to result from a small deletion which removes part of the 3' untranslated region of transcript A, and part of the 5' coding region of transcript B. Fine-structure genetic mapping of the viable unc-60 mutations had previously defined the position of these alleles relative to one another (McKim, et al., 1988, Genetics 118: 49-59). We have determined that two viable alleles, e677 and e723 ,both lie on the same side of the lethal s1586 mutation. This information, in combination with the fine-structure mapping of McKim, et al., indicates that all of the viable alleles affect the same unc-60 transcript (probably A). It is possible, therefore, that the function of this first gene product is only necessary for locomotion, whereas the second gene product may be essential to C. elegans development. PCR amplification and sequencing of DNA from the viable, paralyzed mutants is currently underway, and should allow us to determine the molecular nature of the lesions responsible.

Interestingly, we have shown that a suppressor of the viable unc-60 alleles is also capable of suppressing the lethal allele, s1586 .The phenotype of animals homozygous for sup-12 ( st86 )Xis temperature sensitive sterility (Francis and Waterston, 1985), but these Sup-12 animals are wild-type in terms of movement. The mechanism by which sup-12 suppresses the different unc-60 mutations is unclear at the moment and we are hoping that future molecular analysis of the sup-12 gene will be informative in this regard.