ARL13B and medulloblastoma: We stained a small panel of SHH medulloblastoma samples derived from young patients for ARL13B, a marker for primary cilia (Caspary et al., 2007), and confirmed that there is large variation in the number of ciliated cells between different patients, with some tumors hardly expressing any primary cilia (Fig. 3E) (Gate et al., 2015; Han et al., 2009).