Spermatogenesis is driven by an ordered series of events, which rely on trafficking of specific proteins between nucleus and cytoplasm. The importin α family of proteins mediates movement of specific cargo proteins when bound to importin β. Importin α genes have distinct expression patterns in mouse testis, implying they may have unique roles during mammalian spermatogenesis. Here we use a loss-of-function approach to specifically determine the role of importin α7 in spermatogenesis and male fertility. We show that ablation of importin α7 in male mice leads to infertility and has multiple cumulative effects on both germ cells and Sertoli cells. Importin α7-deficient mice exhibit an impaired Sertoli cell function, including loss of Sertoli cells and a compromised nuclear localization of the androgen receptor. Furthermore, our data demonstrate devastating defects in spermiogenesis including incomplete sperm maturation and massive loss of sperms that are accompanied by disturbed histone-protamine-exchange, differential localization of the transcriptional regulator Brwd1 and altered expression of Rfx2 target genes. Our work uncovers the essential role of importin α7 in spermatogenesis and hence in male fertility.

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