Transcriptional Heterogeneity Reveals a Synaptic Gene Program in Developing and Adult Human Oligodendrocyte Precursor Cells

Human oligodendrocyte precursor cells (OPCs) arise early in gestation and expand broadly during cortical development, yet the extent of their heterogeneity remains poorly defined. Here, we isolated >2,300 highly pure OPCs from post-conceptional week (PCW) 17 human cortex using an optimized PDGFRα-based immunopanning and performed single-cell RNA sequencing. Unsupervised clustering revealed four transcriptionally distinct embryonic OPC subsets, including a previously unrecognized population that expressed genes linked to synaptic development, synaptic signaling, and neuromodulation. This subset - designated embryonic synaptic OPCs (eSyn-OPCs) - comprised approximately 28.5% of all embryonic OPCs in the cortex and was characterized by robust expression of synapse-associated secreted factors (<i>THBS2, WNT5A, WNT7A, PLAT, ACHE</i>) and multiple neurotransmitter receptor subunits. Histological analyses across PCW 12-22 demonstrated that eSyn-OPCs first appear around PCW 15 and are enriched in proliferative germinal zones. Spatial transcriptomics confirmed their localization near neural stem and progenitor cells, suggesting proximal neuron-OPC communication during early cortical assembly. Purified eSyn-OPCs differentiated into mature oligodendrocytes <i>in vitro</i>, confirming their oligodendrocyte lineage identity. Reanalysis of adult human single-nucleus RNA-seq datasets uncovered a transcriptionally analogous OPC subset (adult synaptic OPCs, aSyn-OPCs), though with reduced representation of structural synaptic genes and neurotransmitter receptor diversity compared to eSyn-OPCs. Together, these results identify a synaptically specialized OPC population in both developing and adult human cortex and reveal that eSyn-OPCs possess unexpectedly rich synaptic signaling machinery. These findings suggest that human OPCs may participate directly in neuron-glia communication during early cortical development and raise the possibility of developmental stage-specific roles for eSyn-OPCs in shaping neural circuit formation.