Researchers from the University of Adelaide, in collaboration with several Australian institutions, have uncovered that monotremes—egg-laying mammals like echidnas and platypuses—use a distinct genetic mechanism for sex determination, unlike all other mammals. Published in Genome Biology, the study identifies the AMHY gene as the key player, marking a significant breakthrough in understanding these unique animals.
In most mammals, the SRY gene on the Y chromosome triggers male development. However, monotremes lack this gene entirely. Instead, the team found that the AMHY gene, located on the monotreme Y chromosome, controls sex determination. This discovery solves a two-decade-old mystery about how these animals develop sexually.
Dr. Linda Shearwin, co-lead author from the University of Adelaide, emphasized the importance of the findings: “This research provides the first insight into the genetic control of sexual development in monotremes and supports conservation efforts for these iconic species.”
Unlike other mammalian sex-determining genes that act directly on DNA, AMHY functions as a growth factor, signaling through cell surface receptors—a mechanism previously observed only in some fish and amphibians. This makes it the first known example of such a process in mammals.
“Comparisons between monotreme and human AMH proteins could reveal critical insights into fertility and protein function,” added Dr. Shearwin, highlighting potential future research directions.
The study not only fills a major gap in evolutionary biology but also opens doors to further investigations into AMHY’s unique role. Understanding these mechanisms could aid in conserving monotremes and shed light on broader questions about mammalian reproduction.
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