The development of sexual dimorphism in the Drosophila gonad. M. Van Doren 1, T. DeFalco 1, G. Verney 1, S. Russell 2, A. Jenkins 1. 1) Johns Hopkins Univ, Baltimore, MD; 2) University of Cambridge, Cambridge, UK.
A fundamental problem in biology is how the germ cells develop and are nurtured by the soma so that they can give rise to the next generation of a species. My lab studies the formation of the gonad and how interactions with somatic cells affect germ cell development. One interesting aspect of this problem is that the gonad can produce either an ovary or a testis depending on the sex of the embryo. We are investigating how sex determination leads to sexually dimorphic gonad development.
We find that the embryonic gonad in Drosophila is already sexually dimorphic at the time of initial gonad formation. In males, a group of somatic cells is observed at the posterior of the gonad that is not found in females. These cells express characteristic markers, such as CLIFT and Wnt2in a male-specific manner. Interestingly, these cells also express a Drosophila homolog of Sox9, a gene that is critical for sexual dimorphism in humans, and which appears to play a similar role in a variety of vertebrate species. The male-specific cells are specified posterior to the previously-identified clusters of cells that form the somatic gonad. Prior to gonad formation, these posterior cells appear identical in males and females. However, as the gonad forms, these cells attach to the gonad in males, but disappear in females.
The male-specific cells require both AbdBand dsxfor their proper specification, indicating that these two genes provide a combination of positional information and sexual identity required for gonad sexual dimorphism. Furthermore, AbdBexpression is itself sexually dimorphic. Thus, rather than positional information and sexual identity being separate inputs into this process, the genes that control positional information, such as the homeotic genes, can also be directly affected by the sex determination pathway.