Posttranscriptional Control of Neural Progenitors Temporal Dynamics During Neocortical Development by Syncrip

The development of the mammalian neocortex is precisely regulated by temporal gene expression, yet the temporal regulatory mechanisms of cortical neurogenesis, particularly how radial glial cells (RGCs) sequentially generate deep to superficial neurons, remain unclear. Here, the hnRNP family member Syncrip (hnRNP Q) is identified as a key modulator of superficial neuronal differentiation in neocortical neurogenesis. Syncrip knockout in RGCs disrupts differentiation and abnormal neuronal localization, ultimately resulting in superficial cortical layer defects as well as learning and memory impairments in mice. Single cell RNA sequencing analysis demonstrated that the knockout of Syncrip disrupts the latestage neurogenesis, stalling transcriptional progression in RGCs. Mechanistically, Syncrip maintains the transcription of temporal process related transcription factors by recruiting stabilization complexes through phase separation, crucially regulating the Notch signaling pathway that determines the fate of RGCs. Furthermore, pathogenic human mutations in Syncrip weaken its phaseseparation capability, failing to form stable complexes normally. Thus, Syncrip acts as a mediator of posttranscriptional regulatory mechanisms, governing the fate progression of RGCs and the advancement of intrinsic temporal programs. This study establishes an intracellular mechanism for posttranscriptional regulation of progressive fate determination in cortical neurogenesis. In this study, we aimed to elucidate Syncrips role in E14.5 neural progenitor cells (NPCs) and dorsal cortical development. To achieve this, we performed LACE-seq, RNA-seq, and scRNA-seq. LACE-seq was used to reveal direct RNA targets of Syncrip in cultured NPCs, RNA-seq captured global transcriptomic changes between WT and Syncrip cKO, and scRNA-seq provided single-cell-level insights into cellular diversity and differential gene expression within the developing dorsal telencephalon. By integrating these three datasets, we gained a comprehensive perspective on Syncrip-mediated post-transcriptional regulation, systemic transcriptional shifts, and cell-type-specific effects in the embryonic mouse cortex.哺乳动物新皮层的发育受时序基因表达的精准调控，但皮层神经发生的时序调控机制，尤其是放射状胶质细胞（radial glial cells, RGCs）如何依次生成深层至表层神经元的过程，仍未明确。本研究鉴定出异质性核糖核蛋白（heterogeneous nuclear ribonucleoprotein, hnRNP）家族成员Syncrip（hnRNP Q）是新皮层神经发生中表层神经元分化的关键调控因子。在RGCs中敲除Syncrip会破坏神经元分化进程并引发异常神经元定位，最终导致小鼠皮层表层结构缺陷以及学习记忆能力受损。单细胞RNA测序（single cell RNA sequencing, scRNA-seq）分析显示，Syncrip敲除会干扰晚期神经发生过程，阻滞RGCs的转录进程。机制上，Syncrip通过相分离（phase separation）招募稳定复合物，维持时序过程相关转录因子的转录，关键调控决定RGCs命运的Notch信号通路（Notch signaling pathway）。进一步研究发现，人类Syncrip的致病性突变会削弱其相分离能力，无法正常形成稳定复合物。因此，Syncrip作为转录后调控机制的介导因子，调控RGCs的命运进程以及内在时序程序的推进。本研究阐明了皮层神经发生中渐进性命运决定的转录后调控胞内机制。本研究旨在解析Syncrip在E14.5神经祖细胞（neural progenitor cells, NPCs）及背侧皮层发育中的作用。为此，我们开展了LACE-seq、RNA测序（RNA sequencing, RNA-seq）及scRNA-seq实验。其中，LACE-seq用于揭示培养的NPCs中Syncrip的直接RNA靶标；RNA-seq用于捕获野生型与Syncrip条件性敲除（conditional knockout, cKO）小鼠之间的全局转录组变化；scRNA-seq则从单细胞层面解析发育中的背侧端脑的细胞多样性及差异基因表达情况。通过整合这三套数据集，我们全面获取了Syncrip介导的转录后调控、系统性转录组偏移以及胚胎小鼠皮层中的细胞类型特异性效应的完整研究视角。