Shared and Divergent Transcriptional Programs of Oligodendrocyte Differentiation Across Vertebrate Species Revealed...

A myelination is essential for neural function in the vertebrate central nervous system, yet the molecular details of how the oligodendrocyte differentiation program has evolved remain poorly understood. Here, we performed a cross-species single-cell transcriptomic analysis of oligodendrocyte lineage cells in the spinal cord of five vertebrate species: fugu, mudskipper, chicken, mouse, and human. Pseudotime trajectory analysis revealed a shared oligodendrocyte progenitor cell (OPC) to committed oligodendrocyte precursor (COP) to myelin-forming oligodendrocyte (MOL) differentiation trajectory across all species, and CAME-based cross-species mapping confirmed the homology of OPC and MOL identities, while COP showed reduced mapping in teleosts compared with amniotes. Among stage-specific DEGs, highly shared genes (≥4 species) were organized into four co-expression modules encompassing cell projection organization, myelination, synapse assembly, and ribonucleoprotein biogenesis, with evolutionary core genes (all 5 species) enriched for oligodendrocyte differentiation and Wnt signaling. Strikingly, amniote-exclusive genes were enriched for synaptic vesicle transport, cell projection organization, predominantly at the OPC stage. This asymmetry indicates that amniotes have expanded the oligodendrocyte differentiation program at the progenitor stage, potentially linked to the myelination demands of terrestrial locomotor circuits. Our findings provide insights into how the oligodendrocyte differentiation program has been shaped by both deep evolutionary conservation and lineage-specific adaptation.