The monotreme sex gene is unlike that of all other mammals
Researchers from the University of 新浪彩票, in collaboration with the University of Melbourne, University of Queensland and Monash University, have discovered that the genetic mechanism that determines sex in monotremes is different from all other mammals.
Credit: Ken Hurley.
Monotremes, which include echidnas and platypuses, differ in many aspects of their biology to all other mammals. Most distinctly, they lay eggs into a transient pouch rather than giving birth to live young.
In almost all mammals, male sex-determination occurs via the SRY gene on the male Y chromosome. Monotremes have evolved a totally different sex chromosome system that lacks the SRY gene.
New evidence recently published in strongly supports that sex determination occurs through the Y-localised anti-M眉llerian hormone (AMHY) gene in monotremes.
鈥淭he identity of the sex determination gene of egg-laying mammals has been a mystery for more than 20 years, since it was discovered that monotremes had sex chromosomes very different from those of all other mammals,鈥 says co-lead author Dr Linda Shearwin, from the University of 新浪彩票鈥檚 School of Biological Sciences.
鈥淚n this research, we provide evidence that supports AMHY as the sex determination gene of monotremes and gives the first insight into genetic control of sexual development in these mammals.
鈥淭his new understanding fills a significant knowledge gap and ultimately can be used to support conservation of these iconic Australian mammals.鈥
Not only is the gene that determines sex different in monotremes than in other mammals, it also performs this function differently.
鈥淎ll other known mammalian sex determination genes act directly on the DNA of the cell to switch on the male development pathway genes,鈥 says Dr Shearwin.
鈥淎MHY is a growth factor, which is secreted and acts through a cell surface receptor to change gene expression in cells.
鈥淚n some fish and amphibian species, AMH is the sex determining gene, but AMHY in monotremes would be the first known example of a growth factor playing a sex determining role in mammals.鈥
AMH is an important protein hormone for human fertility, and now that the full details of the AMHX and AMHY proteins in monotremes are known, researchers can compare them with other mammals.
鈥淐omparisons between the proteins of distantly related species, such as monotremes and humans, can give valuable information about what is essential for a protein to be functional.鈥 says Dr Shearwin.
鈥淚n future work we would like to investigate whether the monotreme AMHY growth factor acts differently to other known AMH proteins. This will give functional insight into a unique mammalian sexual development pathway.鈥
Media contact:
Dr Linda Shearwin, School of Biological Sciences, University of 新浪彩票. Phone: +61 0432 961 375 Email: linda.shearwin@adelaide.edu.au
Professor Frank Gr眉tzner, School of Biological Sciences, University of 新浪彩票. Phone: +61 8 8313 4812 Email: frank.grutzner@adelaide.edu.au
Johnny von Einem, Senior Media Officer, University of 新浪彩票. Phone: +61 0481 688 436, Email: johnny.voneinem@adelaide.edu.au
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