Zfp206 (ZNF206 in human) encodes a zinc finger-and SCAN domain-containing protein that is highly expressed in pluripotent ESC. Upon differentiation of human and mouse ESC, Zfp206 expression is quickly repressed. Zfp206 was found to be expressed throughout embryogenesis but absent in adult tissues except testis. We have identified a role for Zfp206 in controlling ESC differentiation. ESC engineered to overexpress Zfp206 were found to be resistant to differentiation induced by retinoic acid. In addition, ESC with knocked-down expression of Zfp206 were more sensitive to differentiation by retinoic acid treatment. We found that Zfp206 was able to enhance expression from its own promoter and also activate transcription of the Oct4 and Nanog promoters. Our results show that Zfp206 is an embryonic transcription factor that plays a role in regulating pluripotency of embryonic stem cells.

It is well known that Oct4 and Sox2 play an important role in the maintenance of embryonic stem cell pluripotency. These transcription factors bind to regulatory regions within hundreds of target genes to control their expression. Zfp206 is a recently characterized transcription factor that has a role in maintaining stem cell pluripotency. We have demonstrated here that Zfp206 is a direct downstream target of Oct4 and Sox2. Two composite sox-oct binding sites have been identified within the first intron of Zfp206. We have demonstrated binding of Oct4 and Sox2 to this region. In addition, we have shown that Oct4 or Sox2 alone can activate transcription via one of these sox-oct elements, although the presence of both Oct4 and Sox2 gave rise to a synergistic effect. These studies extend our understanding of the transcriptional network that operates to regulate the differentiation potential of embryonic stem cells. Embryonic stem cells (ESCs)2 are derived from the inner cell mass of the blastocyst and exhibit both pluripotency and selfrenewing capabilities. For proper developmental outcome, ESCs must tightly regulate their differentiation status, and through continuing study, the molecular basis of that regulation process is beginning to emerge. Systematic, genome-wide interrogations have identified hundreds of genes, including several transcription factors, which have expression patterns tightly correlated with ES cell differentiation (1-6). Two key transcription factors, Oct4 and Sox2, have been identified that are crucial for maintenance of the pluripotent state of ESCs (7,8). ESCs lose the capacity to maintain pluripotency upon knockdown of expression of these transcription factors by RNA interference (9, 10). Gene knock-out studies confirm the importance of Oct4 and Sox2 for early embryonic development. It has been demonstrated by chromatin immunoprecipitation studies that Oct4 and Sox2 bind to a few thousand regulatory sites in the ES cell genome (11,12). It is likely that many of these target genes play a role in modulating ES cell differentiation. Indeed, the transcription factor Nanog, an established regulator of pluripotency, is transcriptionally regulated directly by Oct4 and Sox2 (13).Zfp206 is a transcription factor that is highly expressed in mouse and human ESCs and down-regulated upon differentiation (3, 14). Zfp206 contains a SCAN domain and 14 zinc-finger domains, which suggests that it may be a transcription factor that binds DNA directly. Zfp206 is expressed in the inner cell mass but not in trophectoderm, suggesting that it may play a role in establishing cell fate decisions regarding embryonic versus extraembryonic tissue (15). There is wide temporal and spatial distribution of RNA and protein in the early embryos, indicating that Zfp206 may regulate multiple cell fate decisions (14). Recent data have demonstrated that overexpression of Zfp206 promotes the formation of undifferentiated mouse ESC colonies in vitro (14). We have obtained similar results and further found that overexpression of Zf...

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Transplantation of olfactory ensheathing cells (OECs) is a promising route for CNS repair. There have, however, been major discrepancies between the results from different groups. Part of this can be attributed to variations in cell sources and culture protocols. Accurate estimation of the proportions of OECs and their associated fibroblasts (ONFs) and their evolution with time in culture is an essential baseline for establishing the reparative properties of transplants. In this study, we compare the evolution of cultures from the superficial layers of the olfactory bulb with tissue from the olfactory mucosa, both whole and split into lamina propria and epithelial layer. We used FACS based on p75 and Thy1 to provide a robust and objective numerical estimate of the numbers of OECs and ONFs, respectively in the cultures. A novel four color simultaneous antigenic bivariate cell cycle analysis shows that proliferation of OECs is time-limited, and is unable to prevent an overall loss of OECs with time. Overall, the numbers of OECs in the cultures were inversely correlated with the deposition of fibronectin (FN). Further, culture of the cells purified by flow cytometry shows that, whereas the Thy1 population is terminally differentiated, the p75 population from the mucosal samples generates subpopulations with different antigenic phenotypes, including the reappearance of a subpopulation of p75 cells expressing FN. Culturing epithelial samples at high density reveals an unexpected transient stem cell-like population of rapidly proliferating p75 positive cells.