DNA methylation landscape of Nautilus Pompilius

DNA methylation is a critical epigenetic modification that functions in diverse biological processes. High-throughput sequencing has revealed substantial variations in DNA methylation patterns across species. While extensively studied in vertebrates, knowledge of invertebrate DNA methylation remains limited. We examined the DNA methylation landscape of the ancient-looking marine mollusk, Nautilus pompilius, a "living fossil". We identified key DNA methyltransferase genes (DNMT1 and DNMT3) by homologous searches against the N. pompilius genome and employed whole-genome bisulfite sequencing (WGBS) to characterize methylation patterns. Despite generally similar gene body methylation (gbM) and genome-wide methylation levels to other invertebrates, the N. pompilius exhibits a characteristic low methylation bias specifically in the promoter and first exon regions. N. pompilius has a typical gene body methylation pattern. Both promoter and gene body methylation may work together to regulate gene expression in N. pompilius. Our research provides valuable information to the ever-expanding methylation map of invertebrates.