Transcriptional mechanisms of proneural factors and REST in regulating neuronal reprogramming of astrocytes

Reprogramming offers the possibility to study cell fate acquisitions otherwise difficult to address in vivo. By monitoring the dynamics of gene expression during direct reprogramming of astrocytes into different neuronal subtypes via the activation of Neurog2 and Ascl1, we demonstrate that these proneural factors control largely different neurogenic programs. Among the cascades induced, however, we identified a common subset of transcription factors required for both Neurog2- and Ascl1-induced reprogramming, and combinations of these factors comprising NeuroD4 were sufficient to generate functional neurons. Notably, during astrocyte maturation REST prevents Neurog2 from binding to the NeuroD4 locus that becomes then enriched with histone H4 lysine 20 tri-methylation. As combinations of downstream targets are sufficient to induce reprogramming in Neurog2-resistant cultures, our data support a model of a temporal hierarchy in shutting off alternative fate in astrocyte differentiation. We performed gene expression microarray analysis on cultured postnatal astroctes from cerebral cortex, transduced with Neurog2ERT2 or Ascl1ERT2-encoding retrovirus