Early transcriptome profiling of microRNA-mediated neuronal reprogramming [RNA-seq timecourse]

Neuronal microRNAs, miR-9/9* and miR-124 (miR-9/9*-124), exert reprogramming activities to direct cell-fate conversion of adult human fibroblasts to post-mitotic neurons and enable the generation of discrete neuronal subtypes with additional transcription factors. Previously, the molecular events underlying the neurogenic switch mediated by microRNAs during neuronal reprogramming were unknown. Here, we systematically dissected the neurogenic state induced by miR-9/9*-124 alone and reveal the surprising capability of miR-9/9*-124 in coordinately stimulating the reconfiguration of chromatin accessibilities, DNA methylation and transcriptome, leading to the generation of functionally excitable neurons, yet unbiased towards a particular subtype-lineage. We show that the microRNA-induced neuronal state enables additional transcription factors, ISL1 and LHX3, to selectively commit conversion to a highly homogenous population of human spinal cord motor neurons. Taken together, our study reveals a modular synergism between microRNAs and transcription factors that allows lineage-specific neuronal reprogramming, providing a platform for generating distinct subtypes of human neurons. Overall design: Time series RNA-seq of miRNA-mediated neuronal reprogramming at post-induction day (PID) 0, 3, 6, 10, and 20.