Role of Activin A in regulating ovarian development during vitellogenesis in Japanese eel (Anguilla japonica).

Activin A, a member of the TGF-β superfamily, plays pivotal roles in vertebrate reproductive regulation. This research investigated the biological functions and potential regulatory mechanisms of Activin A during vitellogenesis in Japanese eel. Analysis of the structural characteristics and evolutionary relationships confirmed that Japanese eel Activin A is highly conserved, providing a molecular basis for elucidating its role in ovarian development. Using a prokaryotic expression system, recombinant Japanese eel Activin A protein was successfully produced, and a series of in vitro functional assays were subsequently conducted. Results demonstrated that Activin A significantly promoted vitellogenin uptake by oocytes and enhanced the efficiency of gonadotropin-mediated downstream signaling by upregulating receptor expression during vitellogenesis. Transcriptomic analysis of ovarian cells revealed that Activin A is involved in multiple physiological processes closely associated with ovarian development, including substance transport, energy metabolism, steroid receptor activity, and key reproductive signaling pathways. These findings indicate that Activin A orchestrates ovarian development during vitellogenesis in Japanese eel.