Objective To investigate the expression and the distribution of Dickkopf-like1(Dkkl1)protein during the development of mouse testis.Methods Testes cD NA samples from BALB/c mice in different postnatal days were hybridized with mouse whole genome affymetrix chip to screen the spermatogenesisrelated genes.The characteristics of the selected genes were analyzed by various bioinformatics tools.The mR NA expression of Dkkl1 at different stages of testis development and different tissues in mouse were analyzed by RT-PCR.The protein localization of Dkkl1 in mouse testis was assesed by immunohistochemistry.Results By analyzing the gene chip signals of mouse testis aged 4 d,9 d,18 d,35 d,54 d and 6 months,Dkkl1 was identified with a differential expression in the developmental stages of testis.RT-PCR analysis showed that the expression of Dkkl1 mR NA was firstly detected on 15 d testis tissue and gradually upregulated during the testis developing to the adult stage.The Dkkl1 protein was predominantly located in spermatocytes and round spermatids in mouse testis.Conclusion The expression of Dkkl1 is gradually upregulated during the development of mouse testis and corresponds to the mouse spermatogenesis.It may play a critical role in male mammalian spermatogenesis. Objective To investigate the expression and the distribution of Dickkopf-like1 (Dkkl1) protein during the development of mouse testis. Methods Testes cD NA samples from BALB / c mice in different postnatal days were hybridized with mouse whole genome affymetrix chip to screen the spermatogenesis related genes The characteristics of the selected genes were analyzed by various bioinformatics tools. The mR NA expression of Dkkl1 at different stages of testis development and different tissues in mouse were analyzed by RT-PCR. The protein localization of Dkkl1 in mouse testis was assesed by immunohistochemistry . Results by analyzing the gene chip signals of mouse testis aged 4 d, 9 d, 18 d, 35 d, 54 d and 6 months, Dkkl1 was identified with a differential expression in the developmental stages of testis. RT-PCR analysis showed that the expression of Dkkl1 mR NA was initially detected on 15 d testis tissue and gradually upregulated during the testis developing to the adult stage. The Dkkl1 protein was predomi nantly located in spermatocytes and round spermatids in mouse testis. Confluence The expression of Dkkl1 is gradually upregulated during the development of mouse testis and corresponds to the mouse spermatogenesis. It may play a critical role in male mammalian spermatogenesis.