The establishment of sexual identity in theDrosophilagermline

Abstract

The establishment of sexual identity is a crucial step of germ cell development in sexually reproducing organisms. Sex determination in the germline is controlled differently than in the soma, and often depends on communication from the soma. To investigate how sexual identity is established in the Drosophila germline, we first conducted a molecular screen for genes expressed in a sex-specific manner in embryonic germ cells. Sex-specific expression of these genes is initiated at the time of gonad formation (stage 15), indicating that sexual identity in the germline is established by this time. Experiments where the sex of the soma was altered relative to that of the germline (by manipulating transformer) reveal a dominant role for the soma in regulating initial germline sexual identity. Germ cells largely take on the sex of the surrounding soma, although the sex chromosome constitution of the germ cells still plays some role at this time. The male soma signals to the germline through the JAK/STAT pathway, while the nature of the signal from the female soma remains unknown. We also find that the genes ovo and ovarian tumor (otu) are expressed in a female-specific manner in embryonic germ cells, consistent with their role in promoting female germline identity. However, removing the function of ovo and otu, or reducing germline function of Sex lethal, had little effect on establishment of germline sexual identity. This is consistent with our findings that signals from the soma are dominant over germline autonomous cues at the initial stage of germline sex determination.

DrosophilaAtaxin 2-binding protein 1 marks an intermediate step in the molecular differentiation of female germline cysts

“…Some of these mutations disrupt genes involved in the regulation of sex-specific splicing and germline sexual identity. However, the issue of why defects in sexual identity result in tumorous phenotypes remains largely unresolved (Casper and Van Doren, 2009). Other mutations such as mei-P26 and arrest do not have a clear role in establishing sexual identity, suggesting that disruption of other molecular pathways can also block cyst differentiation.…”

Maintenance of Drosophila germline stem cell sexual identity in oogenesis and tumorigenesis

“…In the absence of Sxl, germ cells develop normally and exhibit the appropriate female-specific behaviors and expression patterns through the end of the larval period (Casper and van Doren, 2009;Chau et al, 2009;Steinmann-Zwicky, 1994). Germ cells, unlike somatic cells, acquire their female identity by a non-cellautonomous mechanism, as demonstrated by studies showing that the gene expression program and behavior of embryonic XX germ cells is masculinized if placed in a male somatic environment (Casper and van Doren, 2009;Horabin et al, 1995;Staab et al, 1996;Wawersik et al, 2005). Dictation by somatic signals continues through the larval stages, after which point XX germ cells control their own sexual development in a cell-autonomous manner.…”

Sex Steroids in Insects and the Role of the Endosymbiont Wolbachia:A New Perspective

“…In the germ line of the D. melanogaster embryo there is evidence for both autonomous and nonautonomous regulation of sexual identity, but non-autonomous signals from the soma are dominant, and germ cells establish their sexual identity as they contact the somatic gonad (Casper & Van Doren, 2009;DeFalco et al, 2008). In fact, XX (i.e.…”