Characterization of β ‐catenin 1 during the gonad development in the common carp ( Cyprinus carpio )

β ‐catenin gene is a pivotal gene for gonad development and maintenance of ovarian function in mammals. However, little is known about its expression and function in gonad development of fish. In this study, a complete c DNA (3342 bp) sequence of β ‐catenin 1 was cloned from the common carp, Cyprinus carpio , by RACE PCR , which encodes a 780‐amino‐acid protein. Quantitative real‐time PCR demonstrated that β ‐catenin 1 m RNA expressions were high in the testis and ovary tissue and the expression increased as the testes developed and the early stage ovaries developed. Western blot results revealed a single immunoreactive band with an estimated molecular weight of 90 kDa in testes. Immunohistochemistry analysis revealed that the β ‐catenin 1 protein was concentrated mainly in the cytoplasm of early development stage of oocyte cells and in the cytomembrane of developing and mature sperm cells. 17β‐Ethinylestradiol injecting intraperitoneally into the fish decreased the relative β ‐catenin 1 m RNA expression level except 1 μg/g 72 hr and 5 μg/g 48 hr of treatments in the ovary by real‐time PCR . These results suggest, for the first time, that β ‐catenin 1 is an essential protein in gonad development and might be involved in ovarian early development of C. carpio .