Abstract：Among a significant number of described cold shock proteins, CIRP (cold-inducible RNA binding protein) has been widely researched. In order to explore the function of CIRP in the development of yak testes，and further provide datas for elucidating the regulatory mechanism by which of CIRP acts in spermatogenesis and testicular function of plateau mammalian, we investigated the dynamic expression of CIRP in yak testis during postnatal development by means of Real-time RT-PCR, Western blot and its cellular localization by the immunohistochemical SABC (strept avidin-biotin complex) method. In this study, whole testes were collected from 1-day-old, 5-month-old, 1-year-old and 3-year-old male yaks. The results showed yak CIRP open reading frame contained 642 bp, encoded for 213 amino acids and their molecular weight was estimated as 23 kD. The cDNA sequences of yak CIRP revealed significant homology of 99.8% with Bos taurus. qRT-PCR (quantitative Real-time PCR) and Western blot results showed that CIRP expressed in the testis of different age yaks in mRNA and protein levels, and increased with age. The immunostaining of CIRP was weakly expressed in the seminiferous tubules and occurred in the spermatogonium of 1-day-old yak testes. Then the immunostaining of CIRP was widely localized in the spermatogonium of 5-month-old yak testes. And in 1-year-old yak testes, primary spermatocyte was observed and positive substances were located in the nucleus of spermatogonium and primary spermatocyte. Additionally, in 3-year-old yak testes which developed well, CIRP expressed strongly in seminiferous tubules, and the positive immunostaining occurred in nucleus of spermatogonium and primary spermatocyte. Nothing was observed in the negative controls. This research suggested that CIRP might play an important role in regulating testicular development and maintaining the proliferation and differentiation of spermatogenic cells.
