Stra8 (Stimulated by retinoic acid gene 8) is a marker gene of meiosis,and is regulated by upstream genes on hypothalamic–pituitary–gonadal axis and controls meiotic initiation.The cDNA fragments of Stra8 gene were cloned from testis tissues of Brandts vole using degenerated primers.The full length cDNA,which was obtained by 5′ and 3′ RACE,is 1478bp in length containing a single open reading frame of 1101bp coding for 366 amino acids with a predicted molecular mass of 41.76kDa.The deduced amino acid sequence exhibits the maximum identity (89.6%) to the Stra8 protein of Microtus ochrogaster.The testis tissues from 64 healthy male adult Brandts voles (body weight over 25g) were sampled in typical grassland of Inner Mongolia during April to September,2010.Gene expression patterns were analyzed by quantitative real-time PCR.Our results showed that gene expression was up-regulated from April to late June,and then down-regulated from July to September.It indicated that the process of spermatogenesis was gradually repressed from late June,and this was consistent with the changes in testes weight.Physiological and molecular evidence all show that late June is the period of highest reproductive activity in male Brandts voles.These results are contributing to our better understanding of the regulatory mechanisms associated with seasonal breeding.