Decoding Cortical Glial Cell Development

Mouse cortical radial glial cells (RGCs) are primary neural stem cells that give rise to cortical oligodendrocytes, astrocytes, and olfactory bulb (OB) GABAergic interneurons in late embryogenesis. There are fundamental gaps in understanding how these diverse cell subtypes are generated. Here, by combining single-cell RNA-Seq with intersectional lineage analyses, we show that beginning at around E16.5, neocortical RGCs start to generate ASCL1+EGFR+ apical multipotent intermediate progenitors (MIPCs), which then differentiate into basal MIPCs that express ASCL1, EGFR, OLIG2, and MKI67. These basal MIPCs undergo several rounds of divisions to generate most of the cortical oligodendrocytes and astrocytes and a subpopulation of OB interneurons. Finally, single-cell ATAC-Seq supported our model for the genetic logic underlying the specification and differentiation of cortical glial cells and OB interneurons. Taken together, this work reveals the process of cortical radial glial cell lineage progression and the developmental origins of cortical astrocytes and oligodendrocytes. ScATAC-seq were performed on FACS sorted GFP+ cells from the E18.5 hGFAP-GFP cortex. ScRNA-seq were performed on FACS sorted RFP+ cells from the P1 IS cortex which were electroporated of pCAG-Cre plasmid at E15.小鼠大脑皮层放射状胶质细胞（radial glial cells, RGCs）是原发性神经干细胞，在胚胎发育晚期可分化产生皮层少突胶质细胞、星形胶质细胞以及嗅球（olfactory bulb, OB）GABA能中间神经元。目前学界对这类多样细胞亚型的产生机制仍存在诸多认知空白。本研究通过将单细胞RNA测序（single-cell RNA sequencing, scRNA-seq）与交叉谱系分析相结合，发现大约在胚胎日16.5（E16.5）时，新皮层RGCs开始产生表达ASCL1与EGFR的顶端多能中间祖细胞（multipotent intermediate progenitors, MIPCs）；此类细胞随后分化为表达ASCL1、EGFR、OLIG2及MKI67的基底型MIPCs。这些基底型MIPCs历经多轮分裂，最终产生绝大多数皮层少突胶质细胞、星形胶质细胞以及部分嗅球中间神经元。后续单细胞转座酶可及性测序（single-cell Assay for Transposase-Accessible Chromatin using sequencing, scATAC-seq）结果验证了我们提出的皮层胶质细胞与嗅球中间神经元特化与分化的遗传调控逻辑模型。综上，本研究阐明了皮层放射状胶质细胞的谱系发育进程，以及皮层星形胶质细胞与少突胶质细胞的发育起源。本研究针对E18.5天的hGFAP-GFP转基因小鼠皮层中经荧光激活细胞分选（fluorescence-activated cell sorting, FACS）得到的GFP阳性细胞开展了scATAC-seq实验；同时针对在胚胎日15（E15）时通过电转染导入pCAG-Cre质粒的P1（出生后第1天）小鼠岛叶皮层中经FACS分选得到的RFP阳性细胞开展了scRNA-seq实验。