Making waves down under: the Australian Developmental Biology Workshop.
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Biomedical subjects
Publications and source records attributed to Peter Koopman.
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The decision of the embryonic gonad to differentiate as either a testis or an ovary is a critical step in vertebrate development. The molecular basis of this decision has been the focus of much study, particularly over the past decade. Here we contrast the knowledge of early gonadal development and the switch to testis differentiation with the lack of molecular understanding of ovarian development at early stages. We review current knowledge regarding mechanisms of ovarian morphogenesis and propose a model for the hierarchical control of development of the fetal ovary, incorporating the few genes already known to be important and several signals or factors that are hypothesised to exist in the early ovary.
XX sex reversal syndromes not involving Sry provide an opportunity to identify and study genes important for sexual development. The polled intersex syndrome (PIS) in goats, which shares some features with blepharophimosis, ptosis, epicanthus inversus syndrome (BPES) in humans, exemplifies such syndromes. BPES is caused by defects in the forkhead transcription factor gene FOXL2, while PIS is caused by a large deletion of goat chromosome 1q43 that affects transcription of the genes Pisrt1 and Foxl2. Pisrt1 is a non-translated gene that has a sexually dimorphic expression pattern in goats. Here, we describe the structure and expression of the mouse Pisrt1 locus, to investigate its likely role in ovarian development more broadly in mammals. This gene showed some sequence similarity, and was found in a similar genomic context, to its goat and human orthologues. Expression analyses indicated that Pisrt1 is transcribed, and its mRNA polyadenylated and exported to the cytoplasm, but no significant open reading frames were found in a 1.5kb mouse genomic region corresponding to goat Pisrt1. Pisrt1 transcripts were expressed very broadly among tissues of the developing mouse embryo, and at similar levels in male and female gonads at each stage examined, as determined by in situ hybridisation and RT-PCR. This profile of expression suggests that Pisrt1 is unlikely to contribute to sex-specific events during gonadal development in mice and that divergent pathways of ovarian development operate among different mammalian species.