The Drosophila mago nashi gene (dm-mago) is required during oogenesis for localization of polar granules and posterior determinants, which in turn affect abdominal segmentation and germ-cell determination (1,2). Our collaborators R. Boswell and co-workers in this department originally showed that a cDNA for the C. elegans homologue,
mag-1, should encode a small protein with 80% identity to the dm-mago product, and that it rescued both grandchildless and embryonic lethal mago nashi phenotypes in flies when driven by the dm-mago promoter. To investigate its function in C. elegans, we attempted to obtain a
mag-1 mutation. PCR screens of mutator strains for a Tc1 insertion at the
mag-1 locus have so far been unsuccessful. We have also tested lethal and sterile mutations representing up to six genes (A. Rose and E. Lambie, personal communications) in the
mag-1 region either for rescue by a
mag-1 genomic fragment or sequencing of the
mag-1 coding region; none appear to be
mag-1. As we reported previously, injection of
mag-1 antisense RNA into N2 results in a Mog (masculinization of germ line)-like phenotype, causing injected hermaphrodites to produce defective oocytes and excess sperm (3). This result suggests that
mag-1 might be required in the decision of oogenesis versus spermatogenesis as well as for oogenesis per se. To further explore the former function, we injected
fem-2(
b245ts) hermaphrodites with
mag-1 antisense RNA and found that it still caused production of defective oocytes but did not induce the Mog phenotype, suggesting that the possible
mag-1 function in germ-line sex determination is upstream of
fem-2. We are currently testing more mutants with feminized germ lines to establish epistatic relationships, as well as continuing to screen for mutations in the
mag-1 gene to better define its function. (1) Boswell, R., Prout, M. and Steichen, J. (1991) Development 113: 373-384. (2) Newmark, P. and Boswell, R. (1994) Development 120: 1303-1313. (3) 1996 West Coast Regional C. elegans Meeting Abstracts, p. 126.