Analysis of Drosophila germline sex determination

Abbie Casper, Mark Van Doren. Dept Biology, Johns Hopkins Univ, Baltimore, MD.

Sex-specific development of the germ cells is critical for the formation of male or female gametes and the continuation of a species. Previous work has shown that the decision to develop as male or female in the germline is regulated by non-autonomous signals from the soma, and by germ cell autonomous cues regulated by germ cell sex chromosome constitution. However, little is known about how and when these signals interact to establish and maintain germ cell sexual identity. Germ cell sex determination has mainly been looked at during later stages of development and in adults, but now new tools are allowing analysis of this process during embryogenesis. To identify genes involved in germline sex determination and development, a molecular screen was conducted looking for genes expressed sex-specifically in the embryonic germ cells. From this screen, eight genes were found to be expressed sex-specifically in the male germ line. Sex-specific expression of some of these genes begins as early as stage 15 of embryogenesis and is clear for all the genes by stage 17. Thus, it is likely that germ cell sexual identity is being established during this time. We are using these genes as indicators of germ cell sexual identity to investigate how somatic signals and germ cell autonomous cues control germ cell sex determination. We are currently investigating how alterations in somatic sex (loss of function and gain of function of transfomer), and mutations thought to affect germ cell autonomous sexual identity (e.g . ovo and ovarian tumor), affect the expression of our sex-specific genes. Lastly, we are investigating the role of these genes in sex-specific germ cell development. Viable mutant alleles of one of our genes affect fertility in both sexes. Mutant males are sterile with a severe depletion of germline stem cells. In conclusion, from analysis of sex-specific germ cell expression we are learning more about how and when initial germ cell sexual identity is established, as well as how germline sexual development is regulated at the molecular level.

 Close Window