Dmrt1 induces the male pathway in a turtle with temperature-dependent sex determination

Abstract

The molecular mechanism underlying temperature-dependent sex determination (TSD) has been a long-standing mystery; in particular, the thermosensitive genetic triggers for gonadal sex differentiation are largely unknown. Here, we have characterized a conserved DM domain gene, Dmrt1, in the red-eared slider turtle Trachemys scripta (T. scripta), which exhibits TSD. We found that Dmrt1 has a temperature-dependent, sexually dimorphic expression pattern, preceding gonadal sex differentiation, and is capable of responding rapidly to temperature shifts and aromatase inhibitor treatment. Most importantly, loss-and gain-of-function analyses provide solid evidence that Dmrt1 is both necessary and sufficient to initiate male development in T. scripta. Furthermore, the DNA methylation dynamics of the Dmrt1 promoter are tightly correlated with temperature and could mediate the impact of temperature on sex determination. Collectively, our findings demonstrate that Dmrt1 is a candidate master male sex-determining gene in this TSD species, consistent with the idea that DM domain genes are conserved during the evolution of sex determination mechanisms.

Müllerian-inhibiting substance (MIS) is both necessary and sufficient for testicular differentiation in Chinese soft-shelled turtlePelodiscus sinensis

“…In non-mammalian vertebrates, estrogen and its synthetase aromatase play an important regulatory role in early gonadal sex differentiation. Exogenous estrogen and aromatase inhibitor (AI) can override the effects of primary sex-determination signals, including genetic and environmental factors, if applied during critical developmental periods (Crews 1994a; Crews 1994b; Smith et al 2003; Schulz et al 2007; Kobayashi et al 2008; Ge et al 2017;). Treatment of AI onto chicken ZW eggs was able to induce upregulation of Dmrt1 , a Z chromosome-linked master sex-determining gene, ultimately resulting in female-to-male sex reversal (Smith et al 2003).…”

“…Chinese soft-shelled turtle Pelodiscus sinensis (P. sinensis) exhibiting ZZ/ZW genetic sex-determining system has been recently emerged as an ideal turtle model for investigating reptilian sex determination and differentiation, due to the well-established genetic modulation technique (Sun et al 2017; Ge et al 2017) and available genome resource (Wang et al 2013). In this study, we found that knockdown of Mis by RNA interference resulted in male-to-female sex reversal in P. sinense .…”

Loss of dmrt1 restores female fates in the absence of cyp19a1a but not rbpms2

“…A key and evolutionarily conserved regulator of male specific gene expression and antagonist of female fates that is necessary for male-specific development is the Double sex and Mab3 related transcription factor, Dmrt1 [11,[43][44][45][46][47][48][49][50]. Mutants lacking dmrt1 develop mostly as fertile females -the opposite phenotype of rbpms2DMs [11].…”

Developmental plasticity in reptiles: Critical evaluation of the evidence for genetic and maternal effects on temperature‐dependent sex determination

“…Ge et al. () recently used lentiviral vectors to manipulate Dmrt1 expression in red‐eared slider turtles. Knockdown Dmrt1 at a male‐producing temperature increased aromatase expression, while overexpression of Dmrt1 at a female‐producing temperature reduced aromatase expression.…”

“…Indeed, temperature effects on Cirbp and Dmrt1 expression occur before changes in aromatase expression in snapping turtles (Rhen et al, 2007;Schroeder et al, 2016). Ge et al (2017) Knockdown of Sox9 mRNA and protein expression at a male-producing temperature reduced Amh expression, showing that Sox9 directly or indirectly regulates Amh. However, Sox9 knockdown did not increase aromatase expression.…”