Bivalve mollusks represent a taxonomically and economically significant clade within Mollusca. However, the regulatory mechanisms governing their embryonic development remain poorly characterized. The dwarf surf clam ( Mulinia lateralis), characterized by a short generation time and high fecundity, has recently gained recognition as an ideal model system for bivalve embryological research. This study explored the epigenetic mechanisms driving embryogenesis in M. lateralis, with a particular focus on the maternal-to-zygotic transition (MZT), by integrating chromatin-state profiling and transcriptomic analysis. For the first time in this species, CUT&Tag was employed to generate high-resolution landscapes of histone modifications H3K4me1, H3K4me3, H3K27me3, and H3K27ac across key developmental stages. The resulting data revealed extensive reprogramming of histone marks, indicating dynamic shifts in chromatin architecture during early embryonic development. Integration with transcriptomic data identified the timing of MZT in M. lateralis between the morula and gastrula stages and highlighted a suite of candidate genes essential for embryogenesis. These findings provide mechanistic insight into chromatin-mediated control of bivalve embryogenesis and establish M. lateralis as a robust platform for epigenomic research in marine invertebrates, with implications for functional gene studies and aquaculture advancement.
双壳类软体动物是软体动物门中一个重要且具有经济价值的类群，但其胚胎发育的基础生物学研究仍较为薄弱。侏儒蛤（ Mulinia lateralis）因其生命周期短、繁殖能力强，近年来被认为是双壳类胚胎学研究的理想模式动物。该研究以表观遗传机制为切入点，结合染色质状态图谱与转录组数据，系统解析了侏儒蛤胚胎发育过程中，尤其是母源-合子转换（maternal-to-zygotic transition, MZT）阶段的关键分子机制。我们首次在侏儒蛤中成功应用CUT&Tag技术，构建了H3K4me1、H3K4me3、H3K27me3和H3K27ac在多个关键发育阶段的高分辨率图谱，揭示了胚胎早期发育过程中染色质修饰的广泛重编程及其动态变化。通过多组学联合分析，我们界定了侏儒蛤MZT发生于桑椹期至原肠期之间，并筛选出一批可能在胚胎发生中具有关键作用的候选基因。该研究不仅加深了对双壳类胚胎表观遗传调控的理解，也为海洋无脊椎动物研究提供了新的技术路径和分析框架。通过确立侏儒蛤的模式动物地位，研究成果有望为双壳类育种与功能基因研究奠定基础，并推动跨物种比较发育生物学的发展。.
Keywords: CUT&Tag; Epigenetic regulations; Histone modifications; Maternal-to-zygotic transition; Mulinia lateralis.