Worm Breeder's Gazette 4(1): 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.
A new gene affecting muscle structure, unc-92, has been identified in C. elegans through the isolation of 2 dominant mutants, ST15 and ST22. Each was isolated in a search for dominant mutations as slow moving heterozygous F1 offspring of a mutagenized parent. unc-92 Phenotype Movement. The early larval stages of the heterozygote, unc-92/+, are capable of movement, but by the L4 stage, the animals are paralyzed. Then, as they mature, they begin to move again, moving reasonably well as adults, although distinctly slower than wild type. The homozygote, on the other hand, is slow, but moves reasonably well through all its developmental stages. Body wall muscle. Polarized light microscopy reveals that the body wall musculature in both mutant heterozygotes and homozygotes is severely disorganized. A few distinct A and I bands are usually present in most muscle cells, but most A bands are not well delineated. Overall birefringence is reduced, and patches of birefringence are visible throughout the muscle. Electron microscopy supports the polarized light observations and suggests that the irregular bright patches may be groups of thin filaments that no longer associate with the thick filaments. Pharyngeal muscle. By both polarized light and electron microscopy, the muscle of the pharynx of the heterozygote appears normal. However, in the mutant homozygote, polarized light shows some longitudinally oriented birefringent material at the edges of the second bulb, in contrast to wild type, in which all the birefringence is radially oriented. Electron microscopy confirms the presence of longitudinally oriented filaments in this position. Pharyngeal function seems to be impaired, since some bacteria pass intact through the entire digestive system of the homozygote, and electron microscopy reveals numerous whole bacteria in the gut of these animals. Growth. Heterozygotes grow rapidly and reach a body size comparable to wild type. Homozygotes grow much more slowly and are smaller than wild type. Map positions of unc-92 and sma-1A 2-factor cross with dpy-11 and st15 in the cis configuration indicates that unc-92 is about 4% from dpy-11 V: 16 dpy recombinants/630 animals = R; and p = 1-(the square root of) 1-3R, since unc-92 homozygotes were not counted. 3-factor crosses. The 3-factor cross data are summarized below. Crosses 3, 4, and 5 indicate that unc-92 is to the left of sma-1, but right of unc-23, and very close to unc-41. These conclusions prompted the last 3-factor cross, which showed that sma-1 is extremely close to unc-41.Complementation with sup-3 (e1405) deletion. st15, st22, and sma-1 all complement the sup-3 deletion, e1405, but wild type recombinants are very rare. Therefore, both unc-92 and sma-1 are close to, but outside of, the deletion. The knowledge that unc-41 is covered by the deletion (Riddle and Brenner, 1978) results in a new version of the mid region of linkage group V: [See Figure 1] [See Figure 2]