SHH and medulloblastoma: In addition, CD200 mRNA levels were significantly elevated in the group 4 (sonic hedgehog/cMYC negative) medulloblastoma subset compared to sonic hedgehog positive (SHH+) and group 3 (cMYC+) subsets (p = 0.001 and p = 0.001 respectively) (Figure 1D) [19,20].