Is Basonuclin essential for Oogenesis

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DESCRIPTION (provided by applicant): Basonuclin, a zinc finger protein of 120 kDa, is likely to be a transcription factor that enhances transcription of ribosomal RNA (rRNA) genes. Its expression is restricted to the germ cells of the testis and ovary, and keratinocytes of the stratified epithelium. It has been long recognized that rRNA gene transcription, a key factor in determining ribosome production, is regulated according to the level of cellular protein synthesis. Certain cellular physiological states, such as proliferation (spermatogenesis) or protein accumulation (oogenesis) require a high level of protein synthesis. Although transcription factors associated with the high level of ribosome synthesis during proliferation have been described, these factors appear to be ubiquitous, whereas cell-type specific regulators of rRNA synthesis have not been reported. Basonuclin, because of its: (1) restricted cell-type distribution, (2) association with the rRNA genes in interphase as well as in mitosis, (3) interaction with the promoter of the rRNA genes, and (4) ability to increase transcription from an rDNA promtor, is likely to be a cell-type specific rRNA transcription factor, the first of its kind; (5) our attempt to knockout basonuclin gene by conventional technique was not successful because the null mutation cannot be transmitted into the germline, suggesting that basonuclin is haploinsufficient for germ cell development. Furthermore, the results of our recent study suggest that basonuclin plays a critical role during mouse oogenesis. Based on these observations, we hypothesize that basonuclin is essential in ribosome biogenesis during early mouse oogenesis. If so, inhibition, or targeted disruption, of the function of basonuclin in an oocyte should perturb its development, or the development of the embryo derived from it. Because of our earlier failure in creating a basonuelin knockout by conventional techniques, in this application, we propose, in a single Specific Aim, to test the feasibility of employing two recently developed conditional gene-disruption techniques. Sub aim 1 will use an RNAi approach to reduce the amount of basonuclin in oocytes; Sub aim 2 will use the Cre recombinase to knockout [the] basonuclin gene in oocytes.