DNA Methylation Machinery in Gastropod Mollusks.

The role of DNA methylation in mollusks is just beginning to be understood. This review synthesizes current knowledge on this potent molecular hallmark of epigenetic control in gastropods-the largest class of mollusks and ubiquitous inhabitants of diverse habitats. Their DNA methylation machinery shows a high degree of conservation in CG maintenance methylation mechanisms, driven mainly by DNMT1 homologues, and the presence of MBD2 and MBD2/3 proteins as DNA methylation readers. The mosaic-like DNA methylation landscape occurs mainly in a CG context and is primarily confined to gene bodies and housekeeping genes. DNA methylation emerges as a critical regulator of reproduction, development, and adaptation, with tissue-specific patterns being observed in gonadal structures. Its dynamics also serve as an important regulatory mechanism underlying learning and memory processes. DNA methylation can be affected by various environmental stimuli, including as pathogens and abiotic stresses, potentially impacting phenotypic variation and population diversity. Overall, the features of DNA methylation in gastropods are complex, being an essential part of their epigenome. However, comprehensive studies integrating developmental stages, tissues, and environmental conditions, functional annotation of methylated regions, and integrated genomic-epigenomic analyses are lacking. Addressing these knowledge gaps will advance our understanding of gastropod biology, ecology, and evolution.