Male-specific function of Dmrt7 by sexually dimorphic translation in mouse testis

Dmrt7 is known to be an essential gene for spermatogenesis but not for oogenesis despite mRNA expression in both testis and ovary. In this study, we examined further expression of Dmrt7 transcript and protein. Northern blot and RT-PCR analysis revealed that there was an alternative splicing variant possessing the entire sequence of intron 1 in adult testis (intron 1 variant), in addition to the mature form of mRNA. In fetal ovary, the intron 1 variant was not expressed whereas the fully spliced form of mRNA was expressed. Immunohistochemical analyses demonstrated that DMRT7 protein was present only in spermatocytes of adult testis but not in fetal ovary. In situ hybridization analyses revealed that the fully spliced form of Dmrt7 mRNA as well as the intron 1 variant were expressed in spermatogonia, spermatids and Sertoli cells in addition to spermatocytes. We also found that poly(A) tails of Dmrt7 mRNA underwent modification of its length from 70 to 440 bp long. Unlike Arbp mRNA, the size variation of poly(A) tails was observed in immature testis in which spermatids were absent. In this study, we demonstrated that Dmrt7 had unique sexually dimorphic expression patterns in transcripts that associated with spermatocyte-specific translation, but not in ovary.