Worm Breeder's Gazette 16(2): 47
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.
MCD Biology, University of Colorado, Boulder, CO
In attempts to find additional alleles of unc-62 (pka ceh-25), we tested e917 on a suggestion from Andrew Chisholm, who had found linkage to LGVL. We confirmed his observations that e917 is a male-rescuable, maternal-effect, partially penetrant, early larval lethal and showed that it failed to complement the maternal-effect lethal allele unc-62(ct344). In experiments to define the e917 molecular lesion, we identified it as a probable inversion by inverse PCR sequencing of religated Sau3AI fragments of e917 genomic DNA. Using further direct PCR sequencing we have confirmed the inversion by sequencing across the break points and further defining its structure. One break point is in the unc-62 region of LGVL, included in cosmid T08H10. The other is on the right arm of V, in a region included in the YAC Y04H4A. The inverted segment near the left break point includes a duplication of 94bp from a region about 700bp to the left of the break point. Therefore the e917 rearrangement, which was originally isolated following 32P-decay mutagenesis, should be designated C (for complex) rather than In. It is possible that there are additional complex features in the inverted region of LGV, and although the strain we have worked with has been backcrossed 3 times, it could possibly still carry lesions on other chromosomes.
In a preliminary test of the prediction that e917 should suppress recombination in the center of LGV, we compared the segregation of recombinant progeny from +/unc-60 dpy-11 and e917/unc-60 dpy-11 heterozygotes. In the former class, 30% of Dpy progeny were non-Unc (n=408); in the latter, 25% of Dpy progeny were non-Unc (n=424). Since unc-60, the left break point, and dpy-11 are located at positions -19, ~ -5, and 0 map units, respectively, the observed 5% difference is consistent with suppression of recombination to the right of the break point (although the recombination frequency we observed between unc-60 and dpy-11 is higher than predicted from the map). If recombination suppression is borne out in further tests with more appropriate markers, e917 should be a useful balancer for genes on LGV between -5 and +5. Since it is a maternal-effect semi-lethal, e917 homozygotes will not take over a population, and because the semi-lethality is male-rescuable it is convenient to generate e917 heterozygotes by mating to a homozygous e917 hermaphrodite.