Characterization and expression of dax1 during embryonic and gonad development in the carp (Cyprinus carpio)

Objective: The purpose of this study is to investigate the role of dax1, which causes adrenal hypoplasia congenita (AHC) with associated hypogonadotropic hypogonadism (HH) and dosage-sensitive sex reversal (DSS) during carp embryogenesis and gonadal development. Methods: The dax1 gene was cloned from ovaries of adult carp using homologous cloning and RACE methods. Expression patterns during embryogenesis and various adult tissues were analyzed using RT-PCR (QRT-PCR) and in situ hybridization (ISH). Results: Expression of dax1 was detected at beginning of the blastula stage and peaked at 80 days post hatching (dph), while expression in the ovary was stable. Expression of dax1 was detected in males and females, and showed sexually dimorphic pattern with high level expression in juvenile male liver and gonad. A dimorphic expression was observed in adult male gonad and heart, but was higher in liver of adult females. Whole-mount in situ hybridization revealed dax1 expression in the developing diencephalon at hatching. Later, at approximately 5 dph, a novel expression of dax1 was observed in the developing hindbrain of carp larvae. Conclusion: These preliminary findings suggest that dax1 is conserved during vertebrate evolution and involved in a wide range of developmental processes including neurogenesis and sex differentiation in vertebrates.