Fig. 6: An inhibitory neuron subtype is present in the tree shrew sSC but not the mouse sSC.

A Visualization of the tree shrew-enriched subtype, Clu.TM03, by species on the integrated UMAP space using log normalization and anchor-based CCA integration. B UMAP plot of integrated dataset using SCTransform normalization and CCA integration. Cluster SCT25 is shown at higher magnification on the right. Left, neurons are colored by cluster identity. Right, neurons are colored by species, with a subpopulation in the top left identified as Clu.TM03. C UMAP plot of integrated dataset using log normalization and RPCA integration. Cluster RPCA25 is shown at higher magnification on the right. Right, neurons are colored by species, with all identified as Clu.TM03. D Volcano plot showing genes with enriched expression in TM03, TM02, or shared by the two clusters. Genes are colored based on thresholds: |log₂FC | > 0.5 and p-value < 1 × 10⁻⁵. Red indicates genes meeting both criteria, blue for log2FC only, green for p-value only, and gray for neither. The analysis was performed using a two-sided Wilcoxon Rank-Sum test with Bonferroni correction for p-value adjustment. E GO enrichment analysis of the genes enriched in Clu.TM03 using a one-sided hypergeometric test with Benjamini-Hochberg correction for multiple comparisons. F GO enrichment analysis of the genes enriched in Clu.TM02 using a one-sided hypergeometric test with Benjamini-Hochberg correction for multiple comparisons. G Volcano plot illustrating genes with enriched expression within or outside TM03. The top two genes, identified by the highest log2 fold change (log2FC) and smallest p-values, are labeled with their respective symbols. The analysis was performed using a two-sided Wilcoxon Rank-Sum test with Bonferroni correction for p-value adjustment. H Percentage distribution of SSI for all genes, genes enriched within TM03, and genes enriched in other clusters. I RNA FISH of Postn and Gad1 in the tree shrew SC. The area in the yellow square is shown at a higher magnification at the bottom, with split channels displayed on the right. Scale bars, 500 μm (left) and 50 μm (bottom and right). J Percentage of Postn + neurons co-expressing Gad1 in the tree shrew SC. Mean ± SEM. n = 10 ROIs; n = 2 animals. K RNA FISH of Postn in a mouse coronal section. The area in the top yellow square is magnified at the top right, whereas the bottom square is shown at the bottom right. Scale bars, 500 μm (left) and 50 μm (right).