The histone demethylase KDM6B regulates temperature-dependent sex determination in a turtle species.

Abstract

Temperature-dependent sex determination is a notable model of phenotypic plasticity. In many reptiles, including the red-eared slider turtle <i>Trachemys scripta elegans</i> (<i>T. scripta</i>), the individual's sex is determined by the ambient temperature during egg incubation. In this study, we show that the histone H3 lysine 27 (H3K27) demethylase KDM6B exhibits temperature-dependent sexually dimorphic expression in early <i>T. scripta</i> embryos before the gonad is distinct. Knockdown of <i>Kdm6b</i> at 26°C (a temperature at which all offspring develop into males) triggers male-to-female sex reversal in >80% of surviving embryos. KDM6B directly promotes the transcription of the male sex-determining gene <i>Dmrt1</i> by eliminating the trimethylation of H3K27 near its promoter. Additionally, overexpression of <i>Dmrt1</i> is sufficient to rescue the sex reversal induced by disruption of <i>Kdm6b</i> This study establishes causality and a direct genetic link between epigenetic mechanisms and temperature-dependent sex determination in a turtle species.