An Investigation of Differential Expression of Transcription Factors in Embryonic Chelydra serpentina, a Turtle with Temperature-Dependent Sex Determination
Carroll, MaryBeth M.
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Temperature dependent sex determination (TSD) is common in many reptile species, but is a process for which a proximate mechanism is unknown. We hypothesized that TSD in Chelydra serpentina, the snapping turtle, is a result of differential expression of transcription factors controlling the production of the hormone-metabolizing enzymes 5 α-reductase and cytochrome P450 aromatase at varying temperatures. The hypothesis was tested by representational difference analysis (RDA) of C. serpentina mRNA extracted from the hormone-concentrating tissues of male and female stage 16-17 embryos. Results of this experiment suggest that there is no measurable difference in the expression of transcription factors for 5 α-reductase and cytochrome P450 aromatase between embryos incubated at male-producing temperature vs. female-producing temperature in the middle third of the TSP. We suspect there may not have been large differences in gene expression of embryos at MPT and FPT because sex in the middle third of the TSP is not yet determined and thus gene expression need not be vastly different. Repeating this experiment with embryos at the beginning of the last third of the TSP may reveal greater differences in gene expression because an embryo's sex is determined at that point. Though the results of this study are not directly applicable, knowledge of this process of sex determination will be useful in understanding evolution of such a mechanism and will greatly aid conservation efforts directed at threatened reptile species.