Sox15 is up regulated in the embryonic mouse testis

The mammalian sex determining region on the Y chromosome, SRY, is the founding member of the SOX gene family. SOX genes share a common DNA-binding motif termed the HMG box and have diverse roles in vertebrate embryonic development and tissue differentiation. Sox15 expression was analysed during mouse embryogenesis by whole-mount in situ hybridisation and Real Time RT-PCR. Sox15 was found to be expressed in developing mouse gonads from 11.5 dpc to 13.5 dpc with a peak of expression at 12.5 dpc. Expression was approximately twice as high in the male gonad as in the female gonad.     

Involvement of Oct3/4 in the enhancement of neuronal differentiation of ES cells in neurogenesis-inducing cultures

Oct3/4 plays a critical role in maintaining embryonic stem cell pluripotency. Regulatable transgene-mediated sustained Oct3/4 expression in ES cells cultured in serum-free LIF-deficient medium caused accelerated differentiation to neuroectoderm-like cells that expressed Sox2, Otx1 and Emx2 and subsequently differentiated into neurons. Neurogenesis of ES cells is promoted by SDIA (stromal cell-derived inducing activity), which accumulates on the PA6 stromal cell surface. Oct3/4 expression in ES cells was maintained by SDIA whereas without it expression was promptly downregulated. Suppression of Oct3/4 abolished neuronal differentiation even after stimulation by SDIA. In contrast, sustained upregulated Oct3/4 expression enhanced SDIA-mediated neurogenesis of ES cells. Therefore, Oct3/4 appears to promote neuroectoderm formation and subsequent neuronal differentiation from ES cells.     

Heterokaryon-based reprogramming of human B lymphocytes for pluripotency requires Oct4 but not Sox2

Differentiated cells can be reprogrammed through the formation of heterokaryons and hybrid cells when fused with embryonic stem (ES) cells. Here, we provide evidence that conversion of human B-lymphocytes towards a multipotent state is initiated much more rapidly than previously thought, occurring in transient heterokaryons before nuclear fusion and cell division. Interestingly, reprogramming of human lymphocytes by mouse ES cells elicits the expression of a human ES-specific gene profile, in which markers of human ES cells are expressed (hSSEA4, hFGF receptors and ligands), but markers that are specific to mouse ES cells are not (e.g., Bmp4 and LIF receptor). Using genetically engineered mouse ES cells, we demonstrate that successful reprogramming of human lymphocytes is independent of Sox2, a factor thought to be required for induced pluripotent stem (iPS) cells. In contrast, there is a distinct requirement for Oct4 in the establishment but not the maintenance of the reprogrammed state. Experimental heterokaryons, therefore, offer a powerful approach to trace the contribution of individual factors to the reprogramming of human somatic cells towards a multipotent state.