Fig. 5: Identification of Cxcr4 and Cxcr7 (Ackr3) and Integrin β1 as candidate molecules that regulate the blood vessel-guided migration.

a UMAP (uniform manifold approximation and projection) visualization of approximately 50,000 single cell RNA-seq data randomly sampled from the full dataset (1.3 million cells) of E18 mouse whole brains. 15 clusters were identified. b Annotation of cell types for the 15 clusters based on gene markers as indicated. Clusters 1, 6 and 11 represent migrating cortical neurons, glial progenitors (astrocyte progenitors and oligodendrocyte progenitors), and endothelial cells, respectively. c Identification of astrocyte-specific chemoattractant receptors (c1) and their candidate ligands secreted from endothelial cells (right). We identified Cxcr4 and Cxcr7 (Ackr3), which are receptors for Cxcl12 secreted from endothelial cells, as candidate molecules that regulate the blood vessel-guided migration. We also identified integrin β family expressed in astrocyte progenitors (c2). logFC, log fold-change of the average expression of astrocyte progenitors versus Cluster 1 (c1, c2), or that of endothelial cells versus all cells (right). P, adjusted p-value. We applied two-sided Wilcoxon Rank Sum test with adjustments for multiple comparisons based on bonferroni correction. (d, e) Expression of Cxcr4 and Cxcr7 in cortical VZ-derived Olig2-positive cells. E15 mouse embryos were electroporated with PB-CAG-EGFP and fixed 3 days later (d, e, left panel). Some Olig2 (detected by immunohistochemistry (d) or HCR (e)) and GFP double-positive cells indicated by arrows were positive for Cxcr4 (HCR, 28.29 ± 3.36%, 131 cells/4 brains, mean ± SEM) and Cxcr7 (HCR, 35.28 ± 4.79%, 141 cells/4 brains, mean ± SEM). Scale bars, 10 µm (d), 20 µm (e).