Transcriptome profiling of microRNA-induced neurons, microRNA-induced motor neurons, and starting fibroblasts [array]. Homo sapiens

Neuronal microRNAs miR-9/9* and miR-124 (miR-9/9*-124) direct cell-fate conversion of adult human fibroblasts to post-mitotic neurons and work in concert with additional transcription factors to enable the generation of discrete neuronal subtypes. 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. We found that miR-9/9*-124 surprisingly stimulate reconfiguration of chromatin accessibility, DNA methylation and mRNA levels, leading to the generation of functionally excitable neurons that are not yet biased towards a particular subtype-lineage. Further subtype identity can be programmed through additional transcription factors. As such, we show ISL1 and LHX3 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: Gene expression was examined in starting human fibroblasts, microRNA-induced neurons (miNs), and microRNA-induced motor neurons (moto-miNs) after 35 days of miR-9/9*-124 and transcription factor expression, in duplicate.