Based on our studies using CRISPR-Cas 9 genome editing in mouse and human G3 MBs, a more thorough understanding of the consequences of tumor-specific epigenetic perturbation is warranted to avoid potentially detrimental therapeutic outcomes of EZH2 or EED inhibitory drugs in patients with medulloblastoma expressing high levels of EZH2. The gene discussed is EZH2; the disease is Mobius syndrome.