Making eggs and ovaries.

Hosted by: Professor Leonie Quinn

Abstract

We are interested in how germ cells transition from mitosis to meiosis, a step critical for fertility in all sexually reproducing organisms. In mice, female germ cells abandon the mitotic cell cycle and enter meiosis during fetal life while male germ cells first initiate meiotic cell division after puberty. It is established that expression of the germ cell-specific transcription factor STRA8 is essential for meiotic onset in both sexes, and there is evidence that Stra8 expression is induced by the signalling molecule retinoic acid (RA). Others have shown that BMP signalling enhances the production of primordial germ cell like cells (PGCLCs) in vitro. We investigated whether this is also true in vivo, genetically deleting a BMP receptor-encoding gene specifically in germ cells. We find independent and complementary functions for STRA8 and BMP signalling at the mitosis to meiosis transition. We are also interested in somatic sex determination and differentiation. We found that the transcription factor NFIX, usually associated with maintenance of stem cell function, and with tumorigenesis, is critical for normal ovarian development and function. Specifically, NFIX is necessary for correct development of the theca cells, the steroidogenic cells of the ovary and for formation of a functional corpus luteum, necessary for implantation of the embryo and maintenance of pregnancy. We are investigating whether NFIX also plays a role in regulation of the hypothalamic-pituitary-gonadal axis in females.

Biography

Associate Professor Josephine Bowles did a PhD in medical parasitology before moving into the field of developmental biology. Her postdoctoral work was done under the mentorship of Peter Koopman at the Institute for Molecular Bioscience, UQ.  During this period, she studied mammalian sex determination and biology of the Sox gene family. As a senior postdoc she began to focus on germ cells and in 2016 moved her team into the School of Biomedical Sciences, UQ. Her research team aims to understand all of the signalling that is necessary to instruct naive mammalian germ cells to embark on either oogenesis or spermatogenesis. Key discoveries include 1) that retinoic acid in the fetal ovarian environment triggers germ cells to embark on meiosis; 2) that testicular germ cell fate is dependent on FGF signalling; and 3) that the Nodal/Cripto signalling pathway is normally active in germ cells of the fetal testis and abnormally active in certain forms of testis cancer. The studies have relevance to medical problems including fertility/infertility and testicular cancer as well as to our understanding of stem cell biology more broadly.