Worm Breeder's Gazette 10(3): 18
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.
Genomic DNA from the region of the her-1 locus was obtained by: (i) transposon-induced reversion of the dominant,gf allele her-1(n695) to generate the recessive lf allele her-1(ct50n695), (ii) identification of a Tc1 insertion, ctP3, tightly linked to the ct50 mutation, (iii) cloning of ctP3 and unique flanking sequences, and (iv) identifying a contig of cosmids (courtesy of A. Coulson and J. Sulston) spanning the ctP3 site (C. elegans Meeting Abstracts, 1987, p. 32). This contig, of >200 kb, was oriented with respect to the genetic map using polymorphisms between DH424 and N2 strains. Using a cDNA mapping technique, transcribed regions in the vicinity of ctP3 have been identified, and one of them has been further characterized as follows. Orientation and rough mapping experiments indicate that the ctP3 site is about 3 kb upstream from the start of transcription. A 1.4-kb HindIII fragment containing almost all of the transcribed sequence hybridizes to two bands on gel blots of RNA from mixed population him-8 (XX and XO) animals: an abundant 0.9-kb and a less abundant 1.3-kb transcript. Both transcripts are also present in gravid him-8 hermaphrodites (containing XX and XO embryos), but are greatly reduced or absent in RNA of mixed population or gravid N2 XX hermaphrodites. Two strong her-1 (lf) alleles, ct50n695 and y10 result in disappearance of the larger transcript, but do not appear to affect the smaller one; two other recessive her-1 mutations, ct22n695 do not appear to affect either transcript. Both transcripts are present in her-1(n695) XX hermaphrodites (which are variably masculinized), but absent from tra-1(e1099) XX animals (which are essentially completely masculinized). These findings are consistent with earlier genetic analysis and with the Hodgkin model, which predicted that for wild-type sex determination, her-1 activity should normally be high in XO animals and low or absent in XX animals, and that this activity should not be required for the masculinization of XX animals caused by tra-1(lf) mutations. Furthermore, our results strongly suggest that the sex-specific activity of her-1 is controlled at the level of transcription, in contrast to the post-transcriptional mechanisms that control autosomal sex-determining genes in Drosophilia. Transcript mapping and sequencing of her-1 genomic and cDNA clones are in progress.