Zhang Xiangmei, Mandric Igor, Nguyen Kevin H, Nguyen Thao T T, Pellegrini Matteo, Grove James C R, Barnes Steven, Yang Xian-Jie
Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, United States.
Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, United States.
Front Cell Dev Biol. 2021 May 13;9:653305. doi: 10.3389/fcell.2021.653305. eCollection 2021.
The developing retina expresses multiple bHLH transcription factors. Their precise functions and interactions in uncommitted retinal progenitors remain to be fully elucidated. Here, we investigate the roles of bHLH factors ATOH7 and Neurog2 in human ES cell-derived retinal organoids. Single cell transcriptome analyses identify three states of proliferating retinal progenitors: pre-neurogenic, neurogenic, and cell cycle-exiting progenitors. Each shows different expression profile of bHLH factors. The cell cycle-exiting progenitors feed into a postmitotic heterozygous neuroblast pool that gives rise to early born neuronal lineages. Elevating or expression accelerates the transition from the pre-neurogenic to the neurogenic state, and expands the exiting progenitor and neuroblast populations. In addition, ATOH7 and Neurog2 significantly, yet differentially, enhance retinal ganglion cell and cone photoreceptor production. Moreover, single cell transcriptome analyses reveal that ATOH7 and Neurog2 each assert positive autoregulation, and both suppress key bHLH factors associated with the pre-neurogenic and states and elevate bHLH factors expressed by exiting progenitors and differentiating neuroblasts. This study thus provides novel insight regarding how ATOH7 and Neurog2 impact human retinal progenitor behaviors and neuroblast fate choices.
发育中的视网膜表达多种bHLH转录因子。它们在未分化的视网膜祖细胞中的精确功能和相互作用仍有待充分阐明。在这里，我们研究了bHLH因子ATOH7和Neurog2在人胚胎干细胞来源的视网膜类器官中的作用。单细胞转录组分析确定了增殖性视网膜祖细胞的三种状态：神经源性前、神经源性和退出细胞周期的祖细胞。每种状态都显示出不同的bHLH因子表达谱。退出细胞周期的祖细胞进入一个有丝分裂后的杂合神经母细胞池，该池产生早期出生的神经元谱系。升高或表达可加速从神经源性前状态到神经源性状态的转变，并扩大退出的祖细胞和神经母细胞群体。此外，ATOH7和Neurog2显著但有差异地增强视网膜神经节细胞和视锥光感受器的产生。此外，单细胞转录组分析表明，ATOH7和Neurog2各自具有正向自调节作用，并且都抑制与神经源性前状态和状态相关的关键bHLH因子，并提高退出的祖细胞和分化中的神经母细胞表达的bHLH因子。因此，本研究为ATOH7和Neurog2如何影响人类视网膜祖细胞行为和神经母细胞命运选择提供了新的见解。
