Although a smaller set of tumors from the GTML model shows a resemblance to Group 4 medulloblastoma and MYCN-driven postnatal stem cells give rise to tumor cells that are positive for the Group 4 KCNA1 marker [20], there are as yet no reliable Group 4 models for medulloblastoma. The gene discussed is KCNA1; the disease is medulloblastoma.