Single-cell Atlas of Human Fetal Cerebellum Decoding Medulloblastoma Origin and Oncogenesis

Medulloblastomas (MBs) are the most common malignant childhood brain tumors, yet the origin of the most aggressive subgroup-3 form remains elusive, impeding development of effective targeted treatment strategies. Previous cell-type analyses of mouse cerebella or human counterparts from frozen tissue nuclei have not fully defined the compositional heterogeneity of MBs. Here, we undertook an unprecedented single-cell profiling of freshly-isolated human fetal cerebella at different developmental stages to establish a reference map for delineating the hierarchical cellular states in MBs. We identified a unique transitional cerebellar progenitor connecting neural stem cells to neuronal lineages in human fetal cerebella. Intersectional analysis revealed that the transitional progenitors were enriched in aggressive MB subgroups, including group-3 and metastatic tumors. Integrated single-cell multi-omic profiling revealed underlying regulatory networks in the transitional progenitor populations, including transcriptional determinants HNRNPH1 and SOX11, which are correlated with clinical prognosis in aggressive group-3 MBs. Genomic profiling and Hi-C analyses identified de novo long-range chromatin loops juxtaposing HNRNPH1/SOX11-targeted super-enhancers to cis-regulatory elements of MYC, an oncogenic driver for group-3 MBs. Targeting the transitional progenitor regulators inhibited MYC expression and MYC-driven group-3 MB growth. Together, our integrated single-cell atlases of human fetal cerebella and MBs reveal important cell populations predisposed to transformation and regulatory circuitries underlying tumor cell state evolution and oncogenesis, highlighting hitherto unrecognized transitional progenitor intermediates predictive of disease prognosis and potential therapeutic vulnerabilities. ### Competing Interest Statement The authors have declared no competing interest.