Efficient genetic reprogramming of unmodified somatic neural progenitors uncovers the essential requirement of Oct4 and Klf4

Significant breakthroughs have been recently achieved in reprogramming somatic cells to a pluripotent embryonic state by the ectopic expression of specific transcription factors. One of the major drawbacks of reprogramming strategies lays in the low efficiency of the process. It is likely that the required complex epigenetic-remodeling events could be cell-type specific and more rational approaches to cell source selection might help to improve the outcome of the procedure. Because the use of somatic stem cells, and specifically neural stem cells (NSCs), as nuclear donors significantly increased the efficiency of somatic cell nuclear transfer, we aimed to determine whether genetically unmodified somatic NSCs could be more easily reprogrammed to pluripotency than unmodified mouse embryonic fibroblasts. Retroviral transduction of the factors Oct4, Sox2, Klf4, and c-Myc successfully reverted NSCs to a pluripotent embryonic stem cell-like state with a 2-fold efficiency increase, faster kinetic, and with a lower number of viral integrations. Quantification analysis of reprogramming-associated genes revealed that NSCs endogenously expressed high levels of Sox2 and c-Myc. Accordingly, NSCs could be successfully induced to pluripotency through the ectopic viral expression of the other two factors (Oct4 and Klf4). These findings suggest that endogenous expression of reprogramming genes could help the reprogramming process and somatic stem cells might be more prone to reprogramming due to their specific genetic background. Genetic-based somatic cell screening might provide essential information for the selection of alternative cell sources more suitable to direct reprogramming