Journal of Experimental Zoology :Molecular & Developmental Evolution
Many reptiles, including the red ‐eared slider turtle (Trachemys scripta), possess a temperaturedependent sex determination (TSD) mechanism where the temperature at which the developing embryos are incubated dictates the gonadal sex of the animal. A number of mammalian gene orthologues have been identified in the sex determination/differentiation cascade of reptiles with TSD although the exact trigger(s) is not well understood. A potential early regulator of gonadal differentiation, Lhx9, controls the proliferation of gonadal cells in mice and its absence prevents gonadal development and drastically reduces the expression of Sf‐1, a gene that regulates the expression of steroidogenic enzymes in the bipotential gonad. In the current study, we cloned Lhx9 from T. scripta and analyzed its expression throughout the thermosensitive period of gonad development using quantitative PCR. We examined the expression profiles of Lhx9 in embryos incubated under control conditions at male ‐ and female‐producing temperatures and with the application of exogenous 17 b‐estradiol or an aromatase inhibitor, Letrozole, to induce sex reversal. The T. scripta Lhx9 cDNA and predicted amino acid sequence showed high homology to those of chicken, anole, and mouse. Lhx9 was expressed at both male‐ and female‐producing temperatures with expression levels increasing throughout the thermosensitive period. Letrozole induced sexreversal did not alter Lhx9 expression levels. 17b‐estradiol treatments appeared to inhibit or delay gonadal differentiation and resulted in lower Lhx9 expression from the presumptive gonadal ridge region. The structural homology and temporal expression pattern of Lhx9 suggests that this represents a conserved element in the gonadal differentiation cascade of T. scripta
genetics, TSD, Temperature Dependent Sex Determination
Animal Sciences | Biodiversity | Biology | Ecology and Evolutionary Biology | Evolution | Genetics | Genetics and Genomics | Marine Biology | Molecular Genetics | Zoology
Kayla L. Bieser, Thane Wibbels, George Mourad, and Frank V. Paladino (2013).
The Cloning and Expression Analysis of Lhx9 During Gonadal SexDifferentiation in the Red‐Eared Slider Turtle, Trachemys scripta,a Species With Temperature‐Dependent Sex Determination. Journal of Experimental Zoology :Molecular & Developmental Evolution.9999B, 1-9. wileyonlinelibrary.com.
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