Reproduction Abstracts

Oct4 and Nanog are the transcription factors responsible for pluripotency maintenance in embryonic stem cells (ESCs), and activation of these genes in differentiated cells is considered the earliest signal of nuclear reprogramming. To date, nuclear reprogramming in somatic cells can be induced by nuclear transfer, induced expression of defined factors (Oct4, c-myc, Sox-2, and Kfl4) and, more recently, by a short exposure to a low pH. However, work in salamander as well as in plants, demonstrated that somatic cell show an intrinsic reprogramming capacity during tissues regeneration. In this work we monitored Oct4 and Nanog expression (by qPCR and immunofluorescence) in sheep/mouse tissues (ear/tail biopsy) and fibroblast primary culture derived from them. Here we report that the simple expansion of fibroblasts in culture dish, without any exogenous stimuli, switches on pluripotency markers. In fact, while Oct4 and Nanog expression was not detected in tissue biopsy, it was widely expressed in cultured fibroblasts. Furthermore, Oct4 and Nanog expression was further increased in response to exposure of GSK3β inhibitor (CHIR99021), a small reprogramming molecule used for ESC self-renewal. From these observations, we believe that reprogramming should be an automatic cell response, triggered when the cells lose the constraints imposed by a multicellular environment. Probably, a complete loss of cell-to-cell and cell-to-matrix communication activates a default gene network that, under certain culture conditions, can leads to pluripotency.