Worm Breeder's Gazette 8(2): 5
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.
We are using a new screen in our efforts to collect and characterize maternal effect lethal mutations. The screen allows for rapid identification of both conditional and non-conditional maternal effect lethals but can also be used to identify fertilization defective and gonad defective mutations. The screen utilizes the fact that fertile vulvaless mutants are consumed from within by their progeny, becoming non-motile bags of worms. If however, for any reason, progeny are not produced by vulvaless worms, the worms will continue to live. Maternal effect lethals, steriles, and gonad defective mutants are identified by scoring F2 on plates from cloned F1 of mutagenized lin-2( e1309); him3(e1147) hermaphrodities. Plates with F2 survivors after three days at 25 C, are candidates. Maternal effect lethals are distinguished from fertilization and gonad defective mutants under the dissecting scope because they accumulate fertilized eggs. Mutations are recovered from the heterozygous siblings and maintained by selection. Males produced by the him-3 mutation are used for outcrosses. We have used two screening strategies. The first screen over the entire genome, was performed to test the feasibility of the screen and to determine a rough estimate of the genomic distribution of the mutations. The second screen utilizes the balancer chromosome C1 to focus on a smaller portion of the genome for saturation analysis. In our first screen, 23 EMS-induced maternal effect lethal mutations were identified from 1600 F1's. Among these are two temperature- sensitive, leaky mutants; the remainder are non-conditional and 100% penetrant. 15 are not rescued by mating to wild type males (strict maternals), 6 are rescued (partial maternals), and two have yet to be tested. The mutations are distributed as follows: LG I-5, LG II-4, LG III-4, LG IV-2, LG V-3, LG X-2 (three remain to be tested). The phenotypes of these mutants are for the most part distinguishable one from the other, and affect such processes as eggshell formation, meiosis, pronuclear migration, P granule segregation, nuclear morphology, cell cycle rate, and cytoplasmic behavior. From the results of this initial screen we conclude that: 1) the method is effective in recovering both strict and partial maternal effect lethal mutations, 2) loci that mutate to maternal effect lethality are numerous, 3) such loci are present on all six linkage groups, 4) and a wide variety of phenotypes can be obtained. The screen utilizing the LGII balancer C1 is the same as above except that the screening strain is lin-2(e1309); 0)/C1,dpy-10( e128)unc-52(e444). This allows us to identify immediately maternal effect linked to chromosome II and balanced by C1. Of 4500 F1's screened thus far, 24 chromosome II maternal effect lethal mutations have been identified. They fall into 16 to 18 complementation groups ( two have yet to be tested) and are evenly distributed over the balanced portion of LG II. Six are allelic to previously identified maternal effect lethal mutations in three genes (we recovered four new alleles at the zyg-9 locus). Preliminary analysis indicates that there is a reasonable mix of strict and partial maternal effects among the mutants, and that complementing alleles show distinguishable phenotypes.