This study investigates the developmental hierarchy in human oligodendroglioma using single-cell RNA sequencing (scRNA-seq). The researchers analyzed 4,347 single cells from six IDH1 or IDH2 mutant human oligodendrogliomas, reconstructing their developmental programs from genome-wide expression signatures. They found that most cancer cells are differentiated along two specialized glial programs, while a rare subpopulation is undifferentiated and associated with a neural stem cell expression program. Cells with proliferation signatures were highly enriched in this subpopulation, suggesting that cancer stem cells (CSCs) are primarily responsible for tumor growth. Copy number variation (CNV) analysis showed that distinct CNV sub-clones within tumors display similar cellular hierarchies, indicating that the architecture of oligodendrogliomas is primarily dictated by developmental programs. Subclonal point mutation analysis supported a similar model, although a full phylogenetic tree would be needed to definitively determine the effect of genetic evolution on the inferred hierarchies. The study provides insights into the cellular architecture of oligodendrogliomas at single-cell resolution and supports the cancer stem cell model, with implications for disease management.This study investigates the developmental hierarchy in human oligodendroglioma using single-cell RNA sequencing (scRNA-seq). The researchers analyzed 4,347 single cells from six IDH1 or IDH2 mutant human oligodendrogliomas, reconstructing their developmental programs from genome-wide expression signatures. They found that most cancer cells are differentiated along two specialized glial programs, while a rare subpopulation is undifferentiated and associated with a neural stem cell expression program. Cells with proliferation signatures were highly enriched in this subpopulation, suggesting that cancer stem cells (CSCs) are primarily responsible for tumor growth. Copy number variation (CNV) analysis showed that distinct CNV sub-clones within tumors display similar cellular hierarchies, indicating that the architecture of oligodendrogliomas is primarily dictated by developmental programs. Subclonal point mutation analysis supported a similar model, although a full phylogenetic tree would be needed to definitively determine the effect of genetic evolution on the inferred hierarchies. The study provides insights into the cellular architecture of oligodendrogliomas at single-cell resolution and supports the cancer stem cell model, with implications for disease management.