Isolation and analysis of genes involved in mouse gonad development.

Abstract

Sex determination in the mammalian embryo is initiated when the bipotential gonad becomes committed to either the testicular or ovarian fate, depending on the presence or absence of the sex determining gene Sry. In the presence of Sry the gonad forms a testis. Sry is expressed in the supporting cells of the gonad and results in the differentiation of Sertoli cells. This process instigates a cascade of gene expression leading to testis cord development and masculinisation of the embryo. Many steps are required for this process. Little is known about these steps or how they are co-ordinated after the expression of Sry. In the absence of Sry the gonad develops into an ovary. Again little is known about ovarian development as the majority of research in this field has focused on the development of the testis. The aim of this project was therefore to find new genes, in new functional classes involved in the development of male and female gonads. The starting point of this project was the use of wholemount in situ hybridisation analyses to validate the expression of candidate sexual development genes. These had been shown to be expressed in a sexually dimorphic manner in the developing gonad using microarrays. Two genes, Gata2 and Vanin-1, were chosen for further study. Gata2 is expressed in the germ cells of the developing ovary and is currently the only gene whose expression is found to be female-specific during gonadogenesis. Vanin-1 is a GPI-anchored cell surface molecule thought to be involved in the migration of bone marrow cells to the thymus. Cell migration is an important feature of testis cord development, therefore Vanin-1 could play similar role in this process. It is expressed in the developing male gonad prior to overt testis cord formation and in the Sertoli cells once they form. Organ culture studies with an anti-Vanin-1 monoclonal antibody showed that cord formation in XY gonads could be blocked in vitro. However, studies of the Vanin-1-/- mouse revealed no overt abnormalities in testis development.