Worm Breeder's Gazette 10(2): 46
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 two genes, egl-15 X and egl-17 X, cause defective sex myoblast (SM) migrations in the hermaphrodite as a result of the repulsion of the SMs by somatic cells in the gonad (C. elegans CSH Meeting Abstracts, 1987, p. 187). Laser ablation of the somatic gonad can rescue the SM migration defects of egl-15 and egl-17 animals, suggesting that the genetic elimination of the repellant could also rescue their phenotypes. However, the original alleles of these genes cause a leaky Egl phenotype, which make reversion experiments difficult. In the last WBG (10(1):115, 1987) we described the isolation of new egl-15 alleles, some of which cause an L1 larval arrest that we think represents the null phenotype . One new allele, n1477, causes a scrawny, Egl phenotype at 20 C and lethality at 25 C. The possibility of easily isolating revertants of the temperature- sensitive lethal phenotype of egl-15(n1477) led us to see if revertants of the lethal phenotype would simultaneously be reverted for the SM migration defect, and, thus, provide a method to identify the repellant genetically. EMS-mutagenized egl-15(n1477) animals were grown at 20 C until the F1's were gravid and then shifted to 25 C. The F2 progeny, representing approximately 75,000 mutagenized haploid genomes, were screened for healthy animals, and 28 revertant strains were recovered. These revertants fall into three classes. (1) Four suppressors are X- linked based upon male transmission. One of these alleles has been shown to be closely linked to egl-15 and is a semi-dominant suppressor of n1477. We suspect that this allele is an intragenic revertant, and are testing to see if the other alleles in this class behave similarly. (2) The 15 suppressors of the second class are recessive and are closely linked to dpy-10 II. Several of these have been separated from n1477 and cause a phenotype in which the worms appear to fill with fluid. The weakest of these phenotypes is a detachment of the intestine from the body wall. The stronger phenotypes are similar, but more severe, and the animals die as L2's or L3's. This phenotype and map position are similar to those of clr-1(e1745ts), originally described by Ed Hedgecock and Andy Fire (C. elegans CSH Meeting Abstracts, 1985, p. 71) . clr-1 (e1745ts) animals display the weak phenotype at 20 C and are dead at 25 C. Suppressors in the second class all fail to complement clr-1(e1745) for its Clr phenotype at 25 C. In addition, clr-1(e1745) suppresses, and is suppressed by, egl-15( n1477) . Thus, n1477 suppressors in this class are alleles of clr-1. ( 3) The remaining nine suppressors are recessive, appear to be linked to dpy-10, and fail to complement for suppression of n1477 by clr-1( n1635) . Thus, they too seem to be clr-1 alleles. However, they are not Clr either isolated away from n1477 nor in trans to clr-1(e1745) and need to be mapped more rigorously. These mutations may define a weaker class of clr-1 alleles. Suppressors in all three classes (nine suppressors examined to date, as well as clr-1(e1745)), partially suppress the migration defect of egl-15(n1477) . In addition, clr-1(e1745) is a good suppressor of the SM migration defect of egl-17(e1313), although the Clr phenotype is not suppressed in the double mutant. The position of the SM's in clr- 1(e1745); 313) animals at 20 C is similar to that in egl-17(e1313) animals with the somatic gonad ablated. Thus, clr-1( e1745) can suppress mutations in both genes that affect the interaction between the SM's and the somatic gonad, although to different extents. The SM migration is not abnormal in clr-1(e1745) animals at 20 C. Since mutations in egl-15 and clr-1 can cause lethality, these genes must be involved in functions besides those controlling the SM migration. Our working model is that egl-15 and clr-1 encode products that control opposing processes, so that the absolute levels of their gene products are not important as long as their relative levels are maintained. These processes may affect both a function controlling the SM migration and at least one other function. This model predicts that null mutations in either gene could not be suppressed. We are currently testing this hypothesis with putative null alleles of egl-15. The weak Clr phenotype can be phenocopied by orthovanadate (Ed Hedgecock, personal communication), a potent inhibitor of ATPases and phosphatases in general. Perhaps clr-1 encodes a phosphatase that opposes a kinase encoded by egl-15 and possibly egl-17.Since we have found that egl-15(n1477) can suppress clr-1 alleles, we are now planning to look for suppressors of clr-1(e1745) with the hope of answering the following questions. First, what type of egl-15 alleles can suppress clr-1(e1745)? Second, can egl-17 mutations suppress the Clr phenotype of clr-1(e1745), and, if so, what type of mutations are they? Third, what other genes can be mutated to suppress clr-1(e1745), and do they affect the SM migration? In addition, we also plan to use the mutual suppression of egl-15 and clr-1 as a means of isolating transposon-tagged and gamma-ray-induced alleles of these genes as the first step towards cloning them.