Temperature-dependent sex determination in reptiles

Sex determination is an attractive research topic because of its greatly diverse mode among animals. Most vertebrates possess genetic sex determination system, whereas some reptiles (all crocodilians examined, most turtles and a few lizard) display Temperature-dependent Sex Determination (TSD), in which homozygous individuals determine sex based on egg incubation temperature. For example, in American alligator, egg incubation at 30°C and lower induces female development, while incubation at slightly higher temperature 33.5°C induces male development. We are investigating the molecular details of TSD mechanisms, including how the temperature signal is received, and general gene expression movements during the sex determination.

We are focusing upon transient receptor potential (TRP) channels as a main initiation candidate for thermal sensor. We found alligator TRPV4 channel is activated in temperatures proximate to alligator TSD. Selective inhibition and activation of TRPV4 channel induces both down and upregulation, respectively, of male gene expression cascade, and higher prominence of Müllerian duct in males by TRPV4 inhibition. This is the first demonstration of thermal sensor that is directly involved with sex determination in a TSD organism and the key role of TRPV4 channels, as a conductor between the environmental stimuli and cellular signaling.