Worm Breeder's Gazette 11(5): 71
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.
Using the screen for maternal effect lethal mutants developed by Ken Kemphues and Jim Priess, we have been looking for mutants whose inviable progeny fail to make gut granules in a manner similar to that described by Diane Morton et al (WBG Vol. 10 #2). With this screen we hope to identify mutations in genes that are required for proper specification of the E lineage. The mutants that we retain from the screen have inviable progeny that divide to >200 cells (approx), are not multinucleate, and do not make gut granules as detected under polarized light. The mutants that we recover from this screen have fallen into three classes: par mutants (par-1, par-3, by Kemphues et al.); those that we are unofficially calling gut mutants (gut defective); and those that we are unofficially calling ggl (gut granuleless). We have concentrated on characterizing mutants of the gut and, to some extent, the ggl classes. From screens of approximately 32,000 EMS-treated haploid genomes and 16,000 gamma-irradiated haploid genomes we have recovered 13 gut mutants and 4 ggl mutants. We have also obtained 3 mutants of the gut class from Diane Morton with whom we are collaborating to characterize this class of mutant. The combined set of gut mutants contains mutations in at least 10 different complementation groups with only two genes represented by more than one allele. The ggl class of mutant is represented by four alleles in a single complementation group. The classification of mutants is based on observations of both early embryogenesis and the terminal phenotype in progeny of mutant hermaphrodites. Embryos of gut mutants divide in a normal asymmetric and asynchronous pattern during very early cell divisions, thus distinguishing them from par mutants. P granules are also segregated normally. Embryonic cell divisions in these embryos appear to be fairly normal in timing and pattern until the beginning of gastrulation. At that time in wild-type development the two E cells' division rate slows and the E cells begin to move into the center of the embryo. In gut mutants the E cells' division rate does not slow and the E. coli's do not gastrulate. These embryos arrest development embryonically as a ball of cells (approx. 400-600 nuclei) with no apparent morphogenesis. As well as lacking gut granules, the embryos fail to produce two antigens that are normally found in differentiated gut cells (assayed by antibodies J126 and SP37 from S. Strome). They do undergo some differentiation; we observe cell-death nuclei, neuronal nuclei, and large amounts of MyoB (anti-myoB from D. Miller). In embryos of ggl mutants early divisions including E cell division and gastrulation appear to be normal. Although these embryos fail to produce gut granules they do make significant amounts of the gut- specific products recognized by SP37 and J126. Since we believe that at least some of the gut genes are most specifically involved in proper specification of the E lineage we are concentrating on further characterizing these genes genetically and molecularly.