How Do Temperature Changes Affect Sex Reversal in Reptiles?

Researchers have shed light on how temperature affects sex reversal in reptiles. In mammals and birds, sex is determined by sex chromosomes, while reptiles and fish lack sex chromosomes and instead have their sex determined by the temperature at a particular stage of development. Despite decades of research, scientists had yet to discover how temperature-induced sex reversal occurs. However, an Australian research team reported that RNA editing influences sex determination.

After studying sex reversal in bearded dragons, a team led by ecologist Dr. Clare Holleley of the Institute for Applied Ecology at the University of Canberra in Australia uncovered how temperature affects reptiles. Female bearded dragons have dissimilar ZW sex chromosomes, while males have a matching pair of Z chromosomes. At 32°C, the chromosome combination determines sex, but at temperatures above 32°C, lizards with male chromosomes undergo sex reversal and become female.

To find out how the lizards undergo sex reversal, Holleley and the research team collected and compared RNA from the reproductive organs and other tissues of males and females. The team observed higher expression of JARID2 and JMJD3, genes in the Jumonji family, in females that had undergone sex reversal.

The team is currently experimenting with lizard embryos to determine when temperature-sensitive RNA first appears. They edited the JARID2 and JMJD3 genes in the lizards’ DNA to learn how they affect embryonic development and whether the absence of these genes can prevent sex reversal.