NeuroD1 is highly expressed in differentiated medulloblastoma cells and has been shown to inhibit tumor growth when overexpressed in animal models.74,103 Our finding that the Sin3A/Hdac1/NeuroD1 complex suppresses Atoh1 expression provides mechanistic insight into NeuroD1’s function in medulloblastoma. The gene discussed is HDAC1; the disease is medulloblastoma.