Specific expression of CC chemokine CCL17 regulates ovarian development and cell cycle in response to female reproductive hormones on in female black rockfish, Sebastes schlegelii

CC chemokine ligand 17 (CCL17) is a CC chemokine present in various species, including fish and mammals. CCL17 plays an important role in various organs, including innate immune defense in mammals, but its role and histological expression in fish have not been elucidated yet. Black rockfish (Sebastes schlegelii) is an economically important aquatic organism in East Asia that has recently been damaged by diverse biological and environmental factors, resulting in enormous financial losses. Although the functions of various immunomodulatory genes in black rockfish have been studied, the histological expression and function of CCL17 from S. schlegelii (SsCCL17) have not been investigated. We conducted homology analysis of the SsCCL17 amino acid sequence in black rockfish by comparing it with those of mammalian, avian, and fish species. Additionally, we proved that SsCCL17 was considerably activated in the ovary and brain of black rockfish using histological analyses via staining with hematoxylin and eosin and in situ hybridization. Moreover, in primary cells collected from the ovarian tissues of black rockfish, cell cycle progression and the expressions of ovarian development-related genes in response to female reproductive hormones were confirmed by quantitative PCR. Finally, the modulatory role of SsCCL17 in ovarian development was assessed using siRNA transfection in primary cells isolated from ovarian tissues of black rockfish, Collectively, we determined the tissue-specific localization of SsCCL17 and its function in the ovary of S. schlegelii, for the first time.