Regulation of REST levels overcomes dysregulation of neural stem cell differentiation caused by disruption of polyubiquitin gene Ubb.

Reduced levels of cellular ubiquitin (Ub) caused by disruption of the polyubiquitin gene Ubb lead to dysregulated differentiation of neural stem/progenitor cells (NSCs) and apoptosis in cells cultured in vitro. However, the underlying mechanisms responsible for these phenotypes in Ub-deficient cells have not been studied extensively. In the present study, we found that levels of repressor element-1 silencing transcription factor (REST) are elevated in Ubb-/- cells. To determine whether dysregulation of NSC differentiation is caused by the increased REST levels, we investigated the effect of reduced REST levels in Ubb-/- cells. Rest knockdown was found to increase the expression of the neuronal marker βIII-tubulin (TUJ1) and restore the expression pattern of the early neuronal marker α-internexin (α-INX) in Ubb-/- cells. Furthermore, Rest knockdown reduced Ub deficiency-induced apoptosis in cells cultured in vitro. Therefore, our study validates that cellular Ub levels are crucial for precise control of the levels of regulatory proteins such as REST during neurogenesis. We propose that regulation of Rest levels is a promising approach to overcome dysregulation of NSC differentiation caused by disruption of the polyubiquitin gene Ubb.