Worm Breeder's Gazette 15(1): 65 (October 1, 1997)
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.
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113, Japan
Human DAZ (Deleted in Azoospermia), mouse Dazla, and Drosophila boule encode a family of proteins with a single RNP-type RNA-binding motif and are thought to be essential for meiosis during spermatogenesis (Nature, 381: 783-785, 1996). The C.elegans cDNA project identified a putative homologue of DAZ/boule. This cDNA (yk62b4, kindly supplied by Yuji Kohara) appears to contain the complete open reading frame for the gene and its predicted amino acid sequence contains a putative RNA-binding domain most similar to Boule, as well as a motif found in all DAZ family members (see figure). We tentatively call this gene Ce-boule . Ce-boule maps close to clr-1 on Chromosome II. To examine whether Ce-boule is involved in meiosis in C. elegans, antisense Ce-boule RNA was injected into gonads of wildtype L4 hermaphrodites. F1 hermaphrodite progeny derived from the injected P0s were sterile at high penetrance. The sterile F1s had normal somatic gonads and normal-looking sperm (by both Nomarski and DAPI staining), but oogenesis was severely affected: with Nomarski microscopy, gonad arms were filled with mostly small nuclei, and none of the cells displayed the characteristic morphology of developing or mature oocytes. By DAPI staining, majority of the nuclei looked similar to mitotic cells. Possible pachytene nuclei were occasionally observed in the proximal arms, but no diplotene-diakinesis nuclei were found. Although the morphology of the nuclei appears mitotic, the phenotype is not tumorous (unlike gld-1(null) or glp-1(gf)), judging from the density of the nuclei in the gonad. The injected P0s themselves showed a similar phenotype after they laid approximately 30 fertilized eggs. Thus, antisense Ce-boule injection seems to affect either the transition from mitosis to meiosis or the early stage of meiosis during oogenesis. The expression pattern of Ce-boule in the adult hermaphrodite germ line was studied by in situ hybridization and it was found that Ce-boule mRNA shows a graded pattern in the gonad. The signal was detected starting at the mitosis/meiosis transition zone and increased in intensity toward the pachytene region.The strong signal was maintained through the proximal arm except in mature oocytes, where the signal was distinctly weaker. No signal was seen in mature sperm. This expression pattern is consistent with the hypothesis that Ce-boule is required during oogenesis, for the meiotic entry and/or the prophase of meiosis I. It is surprising that DAZ/boule's possible counterpart in C.elegans appears to be essential for oogenesis and dispensable for spermatogenesis, as both DAZ and boule seem to be mainly associated with male sterility. For further characterization, we are currently screening for mutants of Ce-boule by a PCR-based method and by looking for sterile mutants in the corresponding chromosomal region. We are grateful to Tim Schedl and Lisa Kadyk for helpful suggestions and guidance.