Oligodendrocyte heterogeneity in the mouse juvenile and adult central nervous system

Abstract

Oligodendrocytes have been considered as a functionally homogeneous population in the central nervous system (CNS). We performed single-cell RNA sequencing on 5072 cells of the oligodendrocyte lineage from 10 regions of the mouse juvenile and adult CNS. Thirteen distinct populations were identified, 12 of which represent a continuum from Pdgfra(+) oligodendrocyte precursor cells (OPCs) to distinct mature oligodendrocytes. Initial stages of differentiation were similar across the juvenile CNS, whereas subsets of mature oligodendrocytes were enriched in specific regions in the adult brain. Newly formed oligodendrocytes were detected in the adult CNS and were responsive to complex motor learning. A second Pdgfra(+) population, distinct from OPCs, was found along vessels. Our study reveals the dynamics of oligodendrocyte differentiation and maturation, uncoupling them at a transcriptional level and highlighting oligodendrocyte heterogeneity in the CNS.

Figure 1. Single cell RNA-Seq analysis of 5072 cells expressing markers of the oligodendrocyte lineage in ten regions of the mouse CNS.

(A) Targeted regions. (B) Number of cells analysed for each region. (C) Hierarchical clustering (left), correlation matrix (middle) and subclass abundances by region (right).

Figure 2. Oligodendrocyte cell states in the continuous maturation process from precursors to mature cells.

(A) t-SNE projection showing the trajectory from OPCs to mature oligodendrocytes. (B) Average (±s.e.m.) expression of marker genes for OPCs, COPs and VLMCs. Representative markers are overlayed on the tSNE map (gray, low expression; red, high expression). (C) smFISH for Sox10, Ctps (MFOL marker) and Klk6 (MOL marker) confirm that these populations are distinct. (D) Immunohistochemistry of COL1A1 (VLMCs), PDGFRA (OPCs and VLMCs) and Tomato LECTIN (blood vessels) in P21 brain. White arrowhead - VLMCs; yellow arrowhead- OPCs (COL1A1-). Scale bar 25μm.

Figure 3. ITPR2+ oligodendrocytes are present in regions of active differentiation and increase in mice undergoing learning in the complex wheel paradigm.

(A) Average (±s.e.m.) expression level of Tcf7l2, Itpr2, Tmem2 and Pdgfa along the oligodendrocyte lineage. (B-C) Immunohistochemistry and quantification of ITPR2+/SOX10+ cells in P7, P21 and P90 brain. One-way ANOVA with Tukey´s multiple comparison test *P<0.05, n=3. (D-E) Immunohistochemistry and quantification of ITPR2+/SOX10+ cells in corpus callosum of P60 non-runners versus runners after 2 days in the complex wheel-learning paradigm (one-tailed Student’s t test). Scale bars 75 μm.

Figure 4. Region and age specific distribution of mature oligodendrocytes

(A) t-SNE projections as in Fig. 2A with colored dots representing cells from each of the ten CNS regions analyzed. (B) Age distribution of OL populations in cortex S1 and corpus callosum. Bar plots show the percentage of each population by age. Red- juvenile brain; blue- adult brain.