Abstract:

【Objective】 The study was aimed to investigate the coding region sequences, their structures and the expression levels of Dmc1 mRNA in yak and cattle-yak testis, so as to offer references for the revealing of the molecular mechanism of infertility of cattle-yak.【Method】RT-PCR was applied to clone the cDNA of Dmc1 gene. The coding region sequences, protein structures and phylogenetic relationships were analyzed by bioinformatics software. Real-time PCR was employed to examine the expression levels of Dmc1 mRNA in yak and cattle-yak testis. 【Result】 The coding region sequences of Dmc1 gene in yak and cattle-yak, had 1 023 bp in length, encoded 340 amino acid residues and showed 100% sequence identity with cattle and above 90% with other mammals. Both yak and cattle-yak’s Dmc1 protein contained the domain II region, which was highly conserved in the E.coli RecA-like protein family, and had the same domain regions as other mammalian Dmc1 proteins. Phylogenetic analysis showed that the cattle, yak and cattle-yak were in the same clustering, and then clustered with canine lupus familiaris, and that human, pan paniscus and macaca mulatta were in another clustering, both of which had a distant relationship with Gallus gallus. Real-time PCR analysis indicated that the difference of expression level of Dmc1 mRNA between yak and cattle-yak was extremely remarkable (P<0.01), and both the Dmc1 mutant and Dmc1-knockout between cattle-yak and mice showed close similarity in phenotypes. 【Conclusion】 It was dedued that Dmc1 protein in cattle might play a key role in meiotic recombination, as which in human and mice. Dmc1 mRNA represented a dramatic difference in expression level between yak and cattle-yak, and the low expression in cattle-yak testis may be related to male infertility of cattle-yak, thus reflecting that Dmc1 might be a candidate gene in male infertility of cattle-yak.

Key words: yak, cattle-yak, Dmc1, male infertility, cloning, sequence analysis, mRNA expression