591B Poster - 08. Patterning, morphogenesis and organogenesis
Friday April 08, 2:00 PM - 4:00 PM

Authors:
Natalie Murphy; Ellen Baxter; Mark Van Doren

Affiliation: Department of Biology, Johns Hopkins University, Baltimore, MD

Keywords:
l. gonads; p. other (somatic support cells)

The Doublesex (Dsx) and Mab-3 Related Transcription factor (DMRT) family proteins are paramount for sex determination in most animals, from planaria to flies, birds, mice, and humans. In Drosophila, the embryonic gonad is formed when a bipotent cluster of somatic gonadal precursors (SGPs) coalesces with the germ cells. Sex determination is regulated by X chromosome dosage, which activates an alternative splicing cascade that yields Dsx^F in females and Dsx^M in males. Both Dsx isoforms have the same DNA binding domain, but they regulate their targets differently to yield sexual dimorphism. Dsx, like mammalian Dmrt1, is first expressed in the somatic gonad during embryogenesis and is required for male vs. female gonad development.

It is known that dsx is expressed in early SGPs during development, but the exact timing and role of Dsx in sex-specific cell fate specification during gonad development is unknown. We are taking a multi-pronged approach to investigate the cell fate decisions that are regulated by Dsx, as well as the target genes it controls to make these decisions. First, we used an endogenously tagged GFP-Dsx to characterize Dsx expression in the somatic gonad. We found that throughout development, males express Dsx in the early somatic support cells (i.e., the hub and early cyst cells), as well as the terminal epithelium. Female Dsx expression is dynamic throughout development. By adulthood, Dsx is limited to the early somatic support cells (i.e., the cap cells and escort cells) – this is a similar pattern as seen in the male. However, at pupal and larval stages, Dsx expression is more promiscuous, and is seen in a wider range of somatic cell types.

This points towards an early “establishment” need for Dsx in some cell types, and a more limited need for “maintenance” as the gonad ages. We will use small dsx LOF clones to further investigate this hypothesis, which cells of the gonad require autonomous sex information, and which cells may be regulated through cell-cell signaling. Ultimately, we aim to elucidate the mechanisms of Dsx in regulating the sex determination of Drosophila gonad somatic stem cell development.