Fig. 1

Schematic illustration of the pituitary-ovary-liver axis for medaka, Oryzias latipes, choriogenesis. Choriogenesis, i.e., chorion formation, includes hepatic expression of genes for chorion components (e.g., structural proteins), transfer of liver-derived proteins into the ovary, and accumulation of the proteins to form the chorions of developing oocytes in the ovary. Abbreviations: Chg(s). – choriogenin(s); ER – estrogen receptor; FSH – follicle-stimulating hormone; STHBG – sex steroid hormone-binding globulin; ZP – zona pellucida (mammalian egg envelope). “Oocyte-specific ZP?” pertains to the question the present study aimed to address since it was previously unknown whether ovarian ZP proteins localize in the medaka chorion or play a role in its function/structure