Development of the germline requires consecutive differentiation events. Regulation of these has been associated with germ cell-specific and pluripotency-associated transcription factors, but the role of general transcription factors (GTFs) remains elusive. TATA-binding protein (TBP) is a GTF involved in transcription by all RNA polymerases. During ovarian folliculogenesis in mice the vertebrate-specific member of the TBP family, TBP2/ TRF3, is expressed exclusively in oocytes. To determine TBP2 function in vivo, we generated TBP2-deficient mice. We found that Tbp2 À/À mice are viable with no apparent phenotype. However, females lacking TBP2 are sterile due to defective folliculogenesis, altered chromatin organization, and transcriptional misregulation of key oocyte-specific genes. TBP2 binds to promoters of misregulated genes, suggesting that TBP2 directly regulates their expression. In contrast, TBP ablation in the female germline results in normal ovulation and fertilization, indicating that in these cells TBP is dispensable. We demonstrate that TBP2 is essential for the differentiation of female germ cells, and show the mutually exclusive functions of these key core promoter-binding factors, TBP and TBP2, in the mouse.[Keywords: TBPL2; TRF3; TBP; Zp3; RNA Polymerase II; ovary] Supplemental material is available at http://www.genesdev.org.

Gametogenesis, the process during which germ cells are generated is essential for reproduction. In mammals, maternal mRNA and proteins present in the oocyte are required to ensure the progression of development until the embryo activates its genome after fertilisation. It is well established that the oocyte synthesises these maternal factors during oocyte growth and then undergoes a quiescent transcriptional period that will be resumed only after fertilisation. However, the mechanisms that govern transcriptional regulation and subsequent silencing during oogenesis are not well understood. Here, we have examined the expression and localisation of the TATA-binding protein (TBP) and the related protein TBP2 (also called TRF3, TBP-related factor 3) during oogenesis and in early mouse embryos. We show that TBP is expressed in the oocytes at the beginning of folliculogenesis, but it is undetectable during further stages of oocyte development, and becomes abundant again only after fertilisation. In contrast to TBP, we found that TBP2 is highly expressed in growing oocytes during folliculogenesis, declines upon ovulation, and is almost undetectable after fertilisation by the two-cell stage. The mirroring localisation profile of TBP and TBP2 suggests different roles for the two proteins in establishing specialised programs of gene expression during oocyte development and in early mouse embryos. Analysis of mutant mouse ovaries in which oocyte-specific factors have been knocked-out suggests that TBP2 is a potential candidate for regulating transcriptional control of oogenesis. Moreover, our results obtained with oocytes lacking the oocyte-specific nuclear chaperone nucleoplasmin 2 suggest that TBP2 function may be related to non-condensed chromatin conformation.

This work was supported by the Centre National de la Recherche Scientifique (CNRS), the Institut National de la Santé et de la Recherche Médicale (INSERM) (Grant Avenir), the Ministère de l'Education Nationale, de l'Enseignement Supérieur et de la Recherche, the Université de Strasbourg, the Association Française contre les Myopathies (AFM) and the Fondation pour la Recherche Médicale (FRM) and Hôpitaux Universitaires de Strasbourg.The authors have nothing to disclose.