Fig. 1: Identification of a non-pyramidal excitatory neuron type in the subiculum.

A scRNA-seq landscape of putative excitatory neurons, with cells colored according to cluster identity and visualized via UMAP dimensionality reduction. B Expression of control genes (top row) and cluster-specific genes (bottom row) for clusters from (A). Results are shown via violin plot, wherein left tick mark denotes zero, and right tick mark denotes maximum value in counts per million (CPM). C Cluster-specific mean values of gene expression for all genes. Differentially expressed genes are colored according to their enriched cluster. D Atlas schematic of a coronal section of the dorsal subiculum. E Expression of Slc17a7 via chromogenic in situ hybridization. Scale bar: 500 µm. Image from Allen Mouse Brain Atlas²⁹. F, G As in (E), but for the cluster-specific marker genes Ly6g6e and Cck. H Expression of Slc17a7, Ly6g6e, and Cck via FISH, with inset illustrating expansion of shown region. Independently repeated across 7 sections from 3 animals. Scale bars: 100 µm overview, 10 µm inset. I Summary of cellular phenotypes for the image in (H). Black denotes non-Slc17a7-expressing cells. J Summary of cellular phenotype distribution for all excitatory cells examined (n = 142,209 total cells; with n = 73,861 Slc17a7-expressing putative excitatory neurons). K Combined Nissl and FISH. Arrows denote phenotype of individual cells. Independently repeated across 2 sections from 2 animals. Scale bar: 10 µm. L Representative cell-body segmentations in yellow. M Cell-body areas for Ly6g6e-expressing and Cck-expressing cells (n = 301 total cells, with n = 102 and 199 total Ly6g6e-expressing and Cck-expressing neurons from n = 2 animals; p = 4.3e-2 via two-sided paired t-test on within-animal-averaged data). Data are presented as mean values ± SEM. N Schematic illustrating calculation of aspect ratios registered to the alveus for the two cells from (L). O As in (M), but for alveus-oriented aspect ratios (p = 4.3e-2 via two-sided paired t-test on within-animal-averaged data). Data are presented as mean values ± SEM. P Principal component analysis of cell-body properties, with points colored according to phenotype from marker gene expression. Cluster 1 (Ly6g6e-expressing) phenotype: 116 cells; cluster 2 (Cck-expressing) phenotype: 185 cells.