Cold-Inducible Rna-Binding Protein as a Potential Regulator of Gonadal Development in the Red-Eared Slider Turtle
Vertebrate sex determination is a process whereby genes define the fate of bipotential gonads during embryonic development. Reptiles of many species exhibit temperature-dependent sex determination (TSD) in which thermal cues trigger gonadal differentiation during the thermosensitive period, approximately the middle third of development. In species with TSD, sexual development is governed by a network of genes that induce male or female gonadogensis in an antagonistic fashion; early in the thermosensitive period, temperature-sensing molecules trigger these sex-specific networks. While the identity of the temperature sensitive genes is largely known, the temperature-sensing molecules have not yet been identified. Cold-inducible RNA-binding protein (Cirbp) is a heat-shock protein within a class of heterogeneous nuclear riboproteins that are activated by temperature. Cirbp has sexually dimorphic, temperature-dependent expression in some reptile species, and has been localized in the medullary cords of early-stage reptile embryos and in the seminiferous tubules of the testes and in the ovarian cortex of late-stage reptile embryos. It is upregulated at female-producing temperatures, concurrent with aromatase (Cyp19) and Forkhead box protein L2 (FoxL2), which have both been positively identified for their involvement in estrogen production in TSD species. As an RNA-binding protein localized to developing gonads, Cirbp may play a regulatory role in embryonic gonadogensis by stabilizing bound pre-mRNA transcripts involved in sex-specific developmental networks. The red-eared slider turtle (Trachemys scripta elegans) exhibits TSD and is sensitive to female-producing temperatures of 31°C and male-producing temperatures of 26°C. Developmental profiles on morphology, recent genomic and transcriptomic advances, and nearly 15 years of data collection on T. s. elegans at our local field site have made it a valuable organism for research on temperature-responsive genes. With a combination of quantitative PCR and existing transcriptome data, we aim to measure Cirbp abundance at female- and male-producing temperatures in T. s. elegans. Our working hypothesis is that Cirbp functions in a dose-dependent fashion to regulate sex-specific differentiation and gonadal development. Using immunoprecipitation and RNA-seq, we further aim to identify transcript targets of Cirbp. We propose that Cirbp binds to transcripts involved in primary sex cord development in early-stage embryos and to those involved in gametogenesis in late-stage embryos. Our approach will introduce traditional biomedical procedures to a non-model organism to investigate the temperature responsiveness of regulatory networks controlling gonadal development in TSD species.
Marroquin-Flores, Rosario, "Cold-Inducible Rna-Binding Protein as a Potential Regulator of Gonadal Development in the Red-Eared Slider Turtle" (2018). University Research Symposium. 92.