Abstract
Chromatin structure plays a pivotal role in maintaining the precise regulation of gene expression. Accessible chromatin regions act as the binding sites of transcription factors (TFs) and cis-elements. Therefore, information from these open regions will enhance our understanding of the relationship between TF binding, chromatin status and the regulation of gene expression. We employed an assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and RNA-seq analyses in the gonads of protogynous hermaphroditic orange-spotted groupers during sex reversal to profile open chromatin regions and TF binding sites. We focused on several crucial TFs, including ZNF263, SPIB, and KLF9, and analyzed the networks of TF-target genes. We identified numerous transcripts exhibiting sex-preferred expression among their target genes, along with their associated open chromatin regions. We then investigated the expression patterns of sex-related genes as well as the mRNA localization of certain genes during sex reversal. We found a set of sex-related genes that—upon further study—might be identified as the sex-specific or cell-specific marker genes that trigger sex reversal. Moreover, we discovered the core genes (gnas, ccnb2, and cyp21a) of several pathways related to sex reversal that provide the guideposts for future study.
Highlights
In teleosts, various patterns of sex determination, including gonochorism, protogynous hermaphroditism, and protandrous hermaphroditism, provide the abundant biological sources for academic and applied studies on sex determination/differentiation and sexual plasticity [1,2,3]
Fish remained in the stage with abundant primary-growth oocyte (PO) and cortical-alveolus stage oocyte (PVO) before MT treatment (Figure 1a)
One week after MT implantation, oocytes in gonads degenerated, and new spermatogenic cysts proliferated, which was defined as the early stage of sex reversion (Week 1, Figure 1c)
Summary
Various patterns of sex determination, including gonochorism, protogynous hermaphroditism, and protandrous hermaphroditism, provide the abundant biological sources for academic and applied studies on sex determination/differentiation and sexual plasticity [1,2,3]. Groupers (Epinephelus) are protogynous hermaphroditic fish that undergo sex change from female to male during their life history [4]. They are considered good models for studying sex differentiation and sex reversal [5]. The orange-spotted grouper (Epinephelus coioides)—one of the many groupers—is an important economic species in Asia [4]. Previous studies reported that many TFs, such as the member of sox (sex determining region Y-box) [7,8,9], wnt (wingless/integrated) [10], dmrt (dsx and mab-3 related transcription factor) [11,12], and nanos [13], play important roles in the process of sex reversal. A comprehensive view of the transcriptional changes during sex reversal remains elusive
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