Sex-Dimorphic Differential Expression Profiles in the Brain of the Adult Chinese Soft-Shelled Turtle, Pelodiscus sinensis

The Chinese soft-shelled turtle (<i>Pelodiscus sinensis</i>) is an economically important species in aquaculture, and its growth pattern is characterized by significant sexual dimorphism. However, the underlying molecular mechanisms of this phenomenon have mostly been investigated in the gonadal tissues of <i>P. sinensis</i>, and there are no articles on sex differentiation from the brain of <i>P. sinensis</i>. Here, we analyzed transcriptomes of the brains of adult male and female <i>P. sinensis</i> using high-throughput Illumina sequencing technology, establishing a set of differential genes and differential transcription factors. The data showed that there were 908 genes with significant differences in expression, of which 357 genes were up-regulated and 551 genes were down-regulated. We annotated using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), and screened some genes and pathways related to growth. There were 282 growth-related differential genes and 181 sex-related differential genes. We screened the genes' growth hormone receptor (<i>GHR</i>) and vascular endothelial growth factor A (<i>VEGFA</i>), which may be related to the growth of <i>P. sinensis</i>. The pathways related to the growth and development of <i>P. sinensis</i> are the growth hormone synthesis, secretion, and action pathway; the MAPK (mitogen-activated protein kinase) pathway; and the calcium signaling pathway. In addition, through gene set enrichment analysis (GSEA), we screened out two genes, LIM homeobox protein 1 (<i>LHX1</i>) and fibroblast growth factor 7 (<i>FGF7</i>), which are related to both growth and sex differentiation, and through protein interaction analysis of these genes, we screened out eight genes, including <i>LHX1</i>, <i>FGF7</i>, <i>GHR</i>, fibroblast growth factor 4 (<i>FGF4</i>), <i>EGFR</i>, <i>BMP3</i>, GLI family zinc finger 2 (<i>GLI2</i>), and neuronal differentiation 1 (<i>NEUROD1</i>), and verified the expression levels of these eight genes in the brain of the <i>P. sinensis</i> by real-time quantitative PCR (qRT-PCR), which supported the reliability and accuracy of our transcriptome analysis. Our study provides a solid foundation for analyzing the mechanisms of sexual-dimorphic growth of <i>P. sinensis</i> and even other turtles.