Transcriptional responses to DHA-induced lipid droplet accumulation in primary adherent mantle cells of Sinonovacula constricta (Lamarck, 1818)

Docosahexaenoic acid (DHA), an essential omega-3 long-chain polyunsaturated fatty acid, is crucial for the development of marine mollusks. Despite its importance, the molecular mechanisms of DHA action in these organisms are poorly understood, primarily due to the lack of reliable in vitro models. This study utilizes the razor clam Sinonovacula constricta as a model organism, establishing a primary adherent cell culture from various tissues, with mantle tissue identified as the optimal source for its rapid migration and low contamination risk. Cells incubated with varying concentrations of DHA (0–400 μM) for 6 h exhibited a concentration-dependent accumulation of lipid droplets (LDs), highlighting the model's suitability for investigating lipid metabolism. Transcriptomic analysis of cells treated with 50 μM DHA identified 848 differentially expressed genes (DEGs), with 747 upregulated and 101 downregulated, indicating the complex effects of DHA. The top 20 significantly upregulated and downregulated DEGs revealed significant involvement in cell signaling transduction, extracellular matrix organization, and substance transport and metabolism. Particularly, lipid metabolism genes, including perilipin 2 and abhydrolase domain containing 2, as well as pathways such as the PPAR signaling pathway and sphingolipid metabolism, were significantly altered, suggesting a reprograming of fatty acid metabolism contributing to LD accumulation. Additionally, pathways related to immune response were notably affected, potentially enhancing cellular health. Collectively, this study provides the first comprehensive insights into the molecular mechanisms underlying DHA-induced LD accumulation in a marine mollusk model at the cellular level, laying a foundation for developing precise nutritional strategies involving DHA in S. constricta aquaculture.