The DNA Demethylase TET1 is a Pivotal Regulator of the miR-124/ISX9-Instructed Conversion of Astrocytes to Induced Neurons

Abstract

The microRNA miR-124 promotes neuronal identity by acting globally, through its multiple targets, at the epigenetic, transcriptional and post-transcriptional levels. We have previously shown that miR-124 acts as a potent driver of the astrocytic fate switch toward an immature neuronal identity, while its supplementation with the neurogenic compound ISX9 enhances in vitro neuronal maturation. Nevertheless, additional cues are needed to enhance the in vivo neurogenic reprogramming capacity of miR-124/ISX9 following neurodegeneration or neurotrauma. In this study, we constructed the core transcriptional regulatory network regulated by miR-124 and ISX9 during astrocyte-to-neuron conversion. Our analysis revealed that the DNA demethylase TET1 is a pivotal transcriptional regulator of the miR-124/ISX9 neurogenic reprogramming process. Silencing of Tet1 impaired the miR-124-mediated neuronal conversion of astrocytes, as well as the ISX9-reinforced differentiation of iNs. We also identified the DNA/RNA binding protein LIN28A as the top mediator of ISX9 neurogenic action and provide evidence that it acts as a coregulator of the expression of synaptic genes, along with TET1. Taken together, our data suggest that TET1 and LIN28A are potent candidates for amplifying miR-124/ISX9 combined in vivo reprogramming action and enhance iNs’ differentiation state.

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