In Vitro and In Vivo Direct Reprogramming of Astrocytes to Induced-Neurons.

Recent studies from a number of groups, including ours, have shown that astrocytes can be directly reprogrammed into induced neurons (iNs) in vitro and in vivo following ectopic overexpression of combinations of transcription factors (TFs), miRNAs, and small chemical molecules. Brain-enriched miRNAs in particular have been recently considered potent reprogramming factors due to their ability to post-transcriptionally modulate high numbers of neurogenic factors and have, thus, been introduced, supplementary or alternatively to TFs, to instruct direct neuronal reprogramming.In this chapter, we describe the methodology for in vitro direct reprogramming of primary mouse astrocytes to differentiated, functional iNs following forced expression of the neurogenic miRNA miR-124 along with the neuronal differentiation-promoting chemical compound Isoexasole-9 (ISX9). Further, we present the methodological procedure for in vivo converting resident activated cortical astrocytes to iNs, following stab wound injury of the mouse cortex and subsequent viral-mediated overexpression of miR-124 in the peritraumatic area along with ISX9 systemic administration.