An unbiased approach to identify genes involved in development in a turtle with temperature-dependent sex determination

<p>Abstract</p> <p>Background</p> <p>Many reptiles exhibit temperature-dependent sex determination (TSD). The initial cue in TSD is incubation temperature, unlike genotypic sex determination (GSD) where it is determined by the presence of specific alleles (or genetic lo...

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Bibliographic Details
Main Authors: Chojnowski Jena L, Braun Edward L
Format: Article
Language:English
Published: BMC 2012-07-01
Series:BMC Genomics
Online Access:http://www.biomedcentral.com/1471-2164/13/308
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Summary:<p>Abstract</p> <p>Background</p> <p>Many reptiles exhibit temperature-dependent sex determination (TSD). The initial cue in TSD is incubation temperature, unlike genotypic sex determination (GSD) where it is determined by the presence of specific alleles (or genetic loci). We used patterns of gene expression to identify candidates for genes with a role in TSD and other developmental processes without making <it>a priori</it> assumptions about the identity of these genes (ortholog-based approach). We identified genes with sexually dimorphic mRNA accumulation during the temperature sensitive period of development in the Red-eared slider turtle (<it>Trachemys scripta</it>), a turtle with TSD. Genes with differential mRNA accumulation in response to estrogen (estradiol-17β; E<sub>2</sub>) exposure and developmental stages were also identified.</p> <p>Results</p> <p>Sequencing 767 clones from three suppression-subtractive hybridization libraries yielded a total of 581 unique sequences. Screening a macroarray with a subset of those sequences revealed a total of 26 genes that exhibited differential mRNA accumulation: 16 female biased and 10 male biased. Additional analyses revealed that <it>C16ORF62</it> (an unknown gene) and <it>MALAT1</it> (a long noncoding RNA) exhibited increased mRNA accumulation at the male producing temperature relative to the female producing temperature during embryonic sexual development. Finally, we identified four genes (<it>C16ORF62, CCT3, MMP2</it>, and <it>NFIB</it>) that exhibited a stage effect and five genes (<it>C16ORF62, CCT3, MMP2, NFIB</it> and <it>NOTCH2</it>) showed a response to E<sub>2</sub> exposure.</p> <p>Conclusions</p> <p>Here we report a survey of genes identified using patterns of mRNA accumulation during embryonic development in a turtle with TSD. Many previous studies have focused on examining the turtle orthologs of genes involved in mammalian development. Although valuable, the limitations of this approach are exemplified by our identification of two genes (<it>MALAT1</it> and <it>C16ORF62</it>) that are sexually dimorphic during embryonic development. <it>MALAT1</it> is a noncoding RNA that has not been implicated in sexual differentiation in other vertebrates and <it>C16ORF62</it> has an unknown function. Our results revealed genes that are candidates for having roles in turtle embryonic development, including TSD, and highlight the need to expand our search parameters beyond protein-coding genes.</p>
ISSN:1471-2164