A major ongoing research trend is concerned with finding alternative reprogramming techniques as well as refining existing ones for induced pluripotent stem cells (iPSCs). A more recent emerging trend focuses on the structural and functional equivalence between iPSCs and human embryonic stem cells and potential clinical and therapeutic implications on regenerative medicine in a long run. The two trends overlap in terms of what they cite, but they are distinct and have different implications on future research. Visual analytics of the literature provides a valuable, timely, repeatable and flexible approach in addition to traditional systematic reviews so as to track the development of new emerging trends and identify critical evidence.

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Basonuclin is a zinc-finger protein found in abundance in oocytes. It qualifies as a maternal-effect gene because the source of preimplantation 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 IImediated transcription, and oocyte morphology was affected (as evidenced by cytoplasmic and cell surface abnormalities). Some of the affected oocytes, however, could still mature to and arrest at metaphase II, and be ovulated. Nevertheless, fertilized basonuclindeficient eggs failed to develop beyond the two-cell stage, and this pre-implantation failure 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.

Abstract. Basonuclin is a protein possessing three pairs of zinc fingers and a nuclear localization signal. Expression of the gene is largely confined to keratinocytes of stratified squamous epithelia and hair follicles. In the epidermis and in stratified epidermal cultures, basonuclin is present in the nuclei of cells in or close to the basal layer but not in the nuclei of cells in more superficial layers. The Ki-67 protein, a nuclear marker for any stage of the multiplication cycle is present in only a subclass of basonuclin-containing cells. In cultured keratinocytes, the disappearance of basonuclin mRNA is associated with loss of colonyforming ability and the appearance of mRNA for involuerin, a protein characteristic of terminal differentiation. In hair follicles, the largest reservoir of basonuclin-containing cells is the outer root sheath, which contains precursors of differentiated cells of the hair shaft and of the epidermis. Basonuclin is not a cell cycle marker but is likely instead to be a regulatory molecule whose presence in the keratinocyte is linked to the maintenance of proliferative capacity and prevention of terminal differentiation.