We offer projects in two areas of research broadly outlined below. Students interested in this research are invited to discuss specific research projects with me.
Function and Evolution of Genes Involved in Sex Determination and Placentation in Mammals
The reproductive biology is one of the most puzzling aspects of monotremes. They are the only egg-laying mammal but they do have a simple placenta which supports the embryo for a short period of time. Monotremes have an extraordinary complex sex chromosomes system that consists of ten sex chromosomes in platypus and nine in echidna. In contrast to sex chromosomes in other mammals, platypus sex chromosomes show extensive homology to bird sex chromosomes. In addition the mammalian sex determining gene SRY is missing in platypus. As the most distant mammalian relative to humans monotremes can provide valuable insights into the evolution of sex determination and placentation genes. We identify and further characterise genes that are involved in these fascinating aspects of reproduction in monotremes, mouse and humans.
Meiotic Organisation of Monotreme Sex Chromosomes
Monotremes feature an extraordinarily complex sex chromosome system that consists of 5X and 5Y chromosomes in platypus and 5X and 4Y chromosomes in echidna. At the first meiotic division the ten sex chromosomes in male platypus (nine in echidna) assemble into a sex chromosomes chain. Over the past five years we have been able to identify these sex chromosomes and show how they are arranged in the chain. We have also shown how they commence pairing in prophase I, how they segregate at anaphase I, and where they reside in mature sperm. Our current work investigates the composition of the synaptonemal complex (formed by proteins that hold chromosomes together at meiosis I). We also investigate if the monotreme sex chromosome complex undergoes sex chromosome inactivation as in other mammals. In addition, we investigate the pattern of meiotic recombination on monotreme sex chromosomes.