TRPV4 modulates sperm motility and fertilization rate in chub mackerel

Achieving efficient fertilization in marine fishes remains a challenge for aquaculture, as the molecular mechanisms linking seawater-derived osmotic and ionic cues to sperm motility remain poorly understood. Here, we investigated the role of the mechanosensitive cation channel TRPV4 in sperm function of chub mackerel (Scomber japonicus), a commercially important species with recently established full life-cycle aquaculture. Quantitative PCR together with TRPV4 immunofluorescence suggested the presence of TRPV4 in sperm, predominantly localized to the midpiece and flagellum. Pharmacological activation of TRPV4 with RN1747 (100 nM) enhanced sperm motility by approximately 6% during the critical 30-50 s post-activation window (p < 0.05), increased amplitude of lateral head displacement (ALH; p < 0.05), and elevated intracellular Ca²⁺ levels approximately twofold (p < 0.05). In contrast, TRPV4 inhibition with RN1734 (1 µM) reduced sperm motility by up to 95% and markedly impaired sperm kinematics and Ca²⁺ dynamics. TRPV4 activation was also associated with increased fertilization and hatching rates, whereas inhibition nearly abolished both (< 1%). Our findings support an important role for TRPV4 in the regulation and maintenance of sperm motility following activation, likely through osmo-ionic and Ca²⁺-dependent signaling pathways. Together, these results extend previous findings from seabream to a scombrid species and suggest that TRPV4-associated sperm regulatory mechanisms may be broadly conserved among marine teleosts. These findings also highlight TRPV4 as a potential pharmacological target for improving fertilization efficiency in marine aquaculture.