Developmental regulation of expression of Ran/M1 and Ran/M2 isoforms of Ran-GTPase in mouse testis.

Two isoforms of Ran-GTPase have been described: Ran/M1 and Ran/M2. Ran/M2 is testis specific, whereas the Ran/M1 isoform is also expressed in somatic tissues. Here we show that both mRNAs, differing in 35 of the 648 nucleotides included in the ORFs, are developmentally regulated during spermatogenesis. Real-time RT-PCR experiments demonstrated that the expression of Ran/M1 and Ran/M2 increased in pachytene spermatocytes with progressive transcript accumulation until they reached the round spermatid stage, in the seminiferous epithelium of adults. In the testis, the expression of both isoforms was found to be restricted to germ cells. An expression window from early pachytene spermatocytes to late round spermatids was detected by in situ hybridization.