MIG Seminar - Jenny Graves - Animal sex determination by genes, chromosomes and the environment
Animal sex determination by genes, chromosomes and the environment
Humans and other mammals have an XX female: XY male system of sex determination, in which a gene SRY on the Y chromosome kick-starts testis-differentiation in the embryo. The testis makes male hormones, which induce male development of the fetus. Birds have a different system of ZZ male: ZW female, in which dosage of a gene DMRT1 on the Z controls sex; the ZW pair is not homologous to the mammal XY. Other reptiles, frogs and fish have different sex chromosome systems and we now know of many distinct sex determining genes which act at different points of the conserved sex determining pathway. This astonishing variety of sex determining genes and chromosomes is the result of the rapid birth and death of sex chromosomes.
Many reptiles and some fish have no sex chromosomes. Sex is determined by environmental factors such as temperature (TSD), through epigenetic changes whose nature has been a longstanding mystery. We work with an Australian dragon lizard, which has a ZW system driven by yet another sex determining gene. However, when it’s hot, all the eggs hatch as females. When ZZ sex reversed females are mated to normal ZZ males, the whole sex determining system flips from GSD to TSD. We have used this system to investigate how TSD works. We found that the transcriptome of ZZ females contains upregulated stress markers and unique transcripts of two epigenetic markers. This suggests that temperature acts, via the stress pathway, to activate epigenetic modifications involved in male determination, providing clues to the mechanism of TSD.
Quinn et al (2010) Science 316: 411 Holleley et al (2015) Nature 523:79 Deveson, Holleley et al (2017) Science Advances 3:e1700731
Professor Jennifer A. Marshall Graves, Distinguished Professor and Vice Chancellor’s Fellow
Professor Jennifer A. Marshall Graves
Distinguished Professor and Vice Chancellor’s Fellow
La Trobe University
Jenny Graves is an evolutionary geneticist who works on Australian animals, including kangaroos and platypus, devils (Tasmanian) and dragons (lizards). Her group uses their distant relationship to humans to discover how genes and chromosomes and regulatory systems evolved, and how they work in all animals including humans. She uses this unique perspective to explore the origin, function and fate of human sex genes and chromosomes, (in)famously predicting the disappearance of the Y chromosome. Jenny received her BSc and MSc from Adelaide University, then a Fulbright Travel Grant took her to the University of California at Berkeley, where she completed her PhD in molecular biology. She joined La Trobe University in 1971 and worked there for many years before moving to ANU in 2001, where she founded and directed the Comparative Genomics department and the ARC Centre of Excellence in Kangaroo Genomics. She returned to La Trobe in 2011 as Distinguished Professor, and was also made a ViceChancellor’s Fellow. She is also is Professor Emeritus at ANU, ThinkerinResidence at Canberra University and Professorial Fellow at the University of Melbourne. Jenny has produced three books and more than 430 research articles. She has received many honours and awards, including the Academy’s Macfarlane Burnet medal in 2006 and an AO in 2010. She is a Fellow of the Australian Academy of Science, and was on the Executive for 8 years, first as Foreign Secretary, then as Education Secretary with responsibility for the Academy's science education projects. She is 2006 L’OrealUNESCO Laureate for Women in Science, and won the 2017 Prime Minister’s Prize for Science (the first woman to win solo).