Single cell transcriptomic analyses reveal the impact of bHLH factors ATOH7 and Neurog2 on human retinal organoid development

Abstract

Transcription factors containing the bHLH motif play critical roles in retinogenesis. However, their precise functions in uncommitted retinal progenitors remain to be fully elucidated. Here, we investigate the roles of ATOH7 and Neurog2 in human ES cell-derived 3D retinal organoids by elevating their expression at the onset of neurogenesis. Using single cell transcriptome analyses, we have identified three progenitor states in retinal organoids: neural stem cell-like progenitors, neurogenic progenitors, and cell cycle-exiting progenitors. The exiting progenitors feed into a postmitotic neuroblast pool that serves as the common source for three early born neuronal lineages. Both ATOH7 and Neurog2 accelerate the transition from the stem cell state to the neurogenic state, and expand the exiting progenitor and neuroblast populations. Despite similar enhancement of retinal ganglion cell production, ATOH7 and Neurog2 show differential promotion of neuronal types with distinct molecular characteristics. Moreover, single cell transcriptome analyses reveal new evidence that ATOH7 and Neurog2 impact uncommitted progenitors through modulation of an interactive gene network, thus providing novel insight into human retinal development.