Basonuclin, which is a zinc-finger protein found in abundance only in the keratinocytes of the stratified epithelium, male germ cells and oocytes, qualifies as a maternal-effect gene because the source of pre-implantation embryonic basonuclin is maternal. Using a transgenic-RNAi approach, we knocked-down basonuclin specifically in mouse oocytes, which led to female sub-fertility. Basonuclin deficiency in oocytes perturbed both RNA polymerase I- and II-mediated transcription and oocyte morphology was affected as evidenced by cytoplasmic and cell surface abnormalities. The affected oocytes, however, could still mature to and arrest at metaphase II and be ovulated, suggesting the impaired pathways were not essential for oocyte development and maturation. Nevertheless, an early embryonic failure in pre-implantation development was identified and likely accounted for the sub-fertility phenotype. These results suggest that basonuclin is a new member of the mammalian maternal-effect genes and interestingly, differs from the previously reported mammalian maternal-effect genes in that it also apparently perturbs oogenesis.