Whole-Genome Methylation Analysis of Female, Male, and Neomale Northern Pike (Esox lucius)

To investigate the effect of epigenetic modifications on sex determination and differentiation in northern pike (Esox lucius), we employed Whole-Genome Bisulfite Sequencing (WGBS) to analyze the DNA methylation patterns in gonadal tissues of females, males, and neomales. First, we obtained high-quality sequencing data, including a total of 410.16 Gb of raw reads and 361.48 Gb of clean reads, with an 86% unique mapping rate, and a bisulfite conversion efficiency of 99.6%. Subsequently, comparative analysis revealed that 66,581 differentially methylated CG regions (i.e., DNA regions with a high frequency of CG dinucleotides), 1215 differentially methylated CHG regions (i.e., DNA regions where CG is followed by another nucleotide), and 3185 differentially methylated CHH regions (i.e., regions where cytosine is methylated in a CHH sequence, with 'H' representing A, T, or C) were identified among the three groups. Furthermore, we identified four key differentially methylated candidate genes (Rspo1, hsd11b2, CYP27A1 and smad3) associated with sex determination and differentiation processes in E. lucius. Finally, by integrating GO and KEGG enrichment analyses, we explored the role of epigenetic modification regulatory networks in the sex determination and differentiation of E. lucius and identified multiple metabolic pathways related to sex determination and differentiation processes (Notch signaling pathway, Wnt signaling pathway and Ovarian steroidogenesis). This study thereby lays a foundation for subsequent functional verification.