Pericyte-to-neuron reprogramming via unfolding of a neural stem cell-like program

Ectopic expression of defined transcription factors can force direct cell fate conversion from one lineage to another in the absence of cell division. Several transcription factor cocktails have enabled successful reprogramming of various somatic cell types into induced neurons (iNs) of distinct neurotransmitter phenotype. However, the nature of the intermediate states that drive the reprogramming trajectory towards distinct iN types is largely unknown. Here we show that successful direct reprogramming of adult human brain pericytes into functional iNs by Ascl1 and Sox2 (AS) encompasses transient activation of a neural stem cell-like gene expression program that precedes bifurcation into distinct neuronal lineages. Intriguingly, during this transient state key signaling components relevant for neural induction and neural stem cell maintenance are regulated and functionally contribute to iN reprogramming and maturation. Thus, AS-mediated reprogramming into a broad spectrum of iN types involves the unfolding of a developmental program via neural stem cell-like intermediates. Single-cell transcriptomes from multiple time points and conditions during direct conversion of human pericytes into induced pericytes through the overexpression of defined factors. Please note that [1] the *ctrl samples represent mock-transfected cells (analyzed along side of the transfected cells) [2] The cell type (for each sample) is provided as 'pericytes or pericyte-derived induced neuronal cells' (as they are in a differentiation continuum from pericytes to neurons due to the treatment protocol) with the combination of 'genotype/variation' and 'time point' information.

异位表达特定转录因子，可在不依赖细胞分裂的前提下，直接介导跨谱系的细胞命运转分化。目前已有多种转录因子组合，成功将多种体细胞重编程为具有不同神经递质表型的诱导神经元（induced neurons, iNs）。然而，驱动重编程轨迹朝向不同诱导神经元亚型的中间细胞状态的本质，仍在很大程度上尚不明确。本研究证实，利用Ascl1与Sox2（以下简称AS）可将成人脑周细胞成功直接重编程为功能性诱导神经元，该过程会先短暂激活类神经干细胞基因表达程序，随后发生谱系分叉，分化为不同的神经元谱系。有趣的是，在这一短暂激活状态中，与神经诱导及神经干细胞维持相关的关键信号成分受到调控，且在诱导神经元重编程与成熟过程中发挥功能性作用。由此可见，通过AS介导将体细胞重编程为多种诱导神经元亚型的过程，需经由类神经干细胞中间态逐步激活发育程序。
本数据集涵盖人类周细胞经特定因子过表达直接转化为诱导周细胞过程中，多个时间点与培养条件下的单细胞转录组数据。
请注意：[1] ctrl样本指空白转染细胞（与转染样本同步开展分析）；[2] 每个样本的细胞类型标注为"周细胞或周细胞来源的诱导神经元细胞"——由于处理方案使细胞处于从周细胞向神经元的分化连续体中，同时会附带标注"基因型/变异"与"时间点"信息。