The inner nuclear envelope (NE) proteins interact with the nuclear lamina and participate in the architectural compartmentalization of chromosomes. The association of NE proteins with DNA contributes to the spatial rearrangement of chromosomes and their gene expression. Sun1 is an inner nuclear membrane(INM) protein that locates to telomeres and anchors chromosome movement in the prophase of meiosis. Here, we have created Sun1^–/– mice and have found that these mice are born and grow normally but are reproductively infertile. Detailed molecular analyses showed that Sun1^–/– P14 testes are repressed for the expression of reproductive genes and have no detectable piRNA. These findings raise a heretofore unrecognized role of Sun1 in the selective gene expression of coding and non-coding RNAs needed for gametogenesis.