Fig. 9

Summary of chorion formation in medakas. Choriogenin (Chg.) expression is induced by estrogen in the liver. Chgs. are secreted into the blood (A: gradient blue arrows) and transferred to the ovary (A), where they accumulate in the chorion by way of the pore canals (B: solid dark blue arrows) after modification. Oocyte-expressed ZPC5 (A) and possibly other ZPs pass through the oocyte plasma membrane (B: green arrows) and accumulate in the chorion. It is still unknown if ZPC5 accumulates in the chorion through the pore canals