Ian Potter Professor of Zoology
University of Melbourne  Presentation TitleSex, Development and Fossil Genes AbstractMarsupials differ from eutherian mammals in their mode of reproduction. Their young are born at a very early stage of development and complete their growth in a pouch, or marsupium. They produce the smallest young, have the longest sperm, the longest period of embryonic diapause, the shortest pregnancy, become sexually differentiated after birth and have the most sophisticated lactation with a changing milk composition throughout the lengthy period of lactation of any mammal. Understanding the control of many of these processes is burgeoning. Embryonic diapause occurs in about 100 mammals, but the marsupial blastocyst enters diapause as a 100 unilaminar cell layer, whereas the eutherian blastocyst has an inner cell mass and thus the embryonic and placental tissues are already identifiable. Marsupials have a fully functional placenta that expresses imprinted genes as in eutherians, suggesting that genomic imprinting has a common origin in all therian mammals. In contrast to eutherians, some marsupial sexual dimorphisms are hormone independent, instead depending on a gene or genes on the X-chromosome. The neonatal marsupial is born with an immature immune system, so is an ideal recipient for xenografts. Testes grafted into neonatal females induce the recipient's ovaries to take on a testicular appearance, while testicular sex reversal can be achieved after administration of oestrogen to prematurely-born male neonates. Sexual differentiation occurs post-natally in distinct stages separated by wide windows of time, so is amenable to experimental manipulation. Early exposure to androgens hormonally imprints the brain and also the development of the prostate and phallus. Marsupials and eutherians diverged about 130 million years ago, but each developed a differing mode of reproduction. Current sequencing of the genome of two marsupial species will tell us much about the way in which these mammalian lineages evolved their separate, but equally successful reproductive strategies. However, the genomes can also be used in other ways. We have recently used our new knowledge to resurrect a gene from an extinct mammal – the thylacine – and express it in a living organism – the mouse. BiographyMarilyn graduated of the Australian National University and completed her PhD under the supervision of Hugh Tyndale-Biscoe. She subsequently held a Fulbright, postdoctoral fellowship at the University of Tennessee, a Ford Foundation Fellowship at the ARC Institute of Animal Genetics, University of Edinburgh before becoming a foundation member of staff of Murdoch University. She resigned her Associate Professor position to move to Monash University as a National Health and Medical Research Council Principal Research Fellow from 1982-1991. She was appointed to the Ian Potter Chair of Zoology and Head of Department at the University of Melbourne, a position she held from 1991-2003. She became a Laureate Professor of the University in 2002, and in 2003 was awarded a Federation Fellowship. She has received the Gottschalk Medal (Australian Academy of Science), the Mueller Medal (ANZAAS) and the Gold Conservation Medal for 2000 of the Zoological Society of San Diego. She received the Whitley Book award in 1987 with Hugh Tyndale-Biscoe for their textbook Reproductive Physiology of Marsupials. She was elected a Fellow of the Australian Academy of Science in 1997, and a Fellow of the Australian Institute of Biology in 1998, was Chair of the Society for Reproductive Biology 1997-2000 and the Australian Antarctic Division’s Ethics Committee from 1997-2003, and currently serves on the Prime Minister’s Science Prizes Committee. Marilyn is currently Director of the ARC Centre for Excellence for Kangaroo Genomics. ResearchThe central focus of research in my laboratory is to understand the control of reproduction and development in mammals. We study a wide range of mammals, from wallabies to women, but I have special interests in the Australian mammalian fauna, particularly marsupials and monotremes and the evolution of reproduction. Reproductive projects funded by the ARC we are currently conducting are on physiology and endocrinology of parturition, the uterine, hormonal and metabolic control of embryonic diapause, embryo culture, the lactational and seasonal control of breeding and biology of germ cells. We have a large NHMRC funded program on the developmental biology of sexual differentiation in marsupials and the genes and hormones that control male and female development. We also have an ARC and ARC SPIRT supported program on conservation and fertility control of macropodid marsupials. Further InformationResearch Article
|