Hybrid cell extinction and re-expression of Oct-3 function correlates with differentiation potential.

The Oct-3 gene is expressed in highly undifferentiated cells and is implicated in mammalian early embryogenesis. We have generated a series of hybrid cells between pluripotent embryonal carcinoma cells (Oct-3+) and fibroblasts (Oct-3-), and have studied the regulation and function of Oct-3. Upon fusion, the hybrid cells differentiated to nestin+/Brn-2+ cells resembling neuroepithelial stem cells. Expression of Oct-3 was extinguished at the transcriptional level in all the hybrid cells examined. The Oct-3 modulating activity required for the Oct-3-mediated enhancer activation was also extinguished. When the Oct-3 transactivating function was introduced into the hybrid cells, they transformed into morphologically distinct nestin-/Brn-2- cells ('revertants'). When the 'revertant' cells subsequently lost Oct-3 expression, they differentiated back to nestin+/Brn-2+ cells. The close correlation between the phenotypic changes and the gain/loss of Oct-3 function indicates that Oct-3 can induce dedifferentiation of the neural cells.