Our results are in full agreement with those of Rohatgi and co-workers, who reported that a second step is required after Smo enrichment in cilia for full Hh pathway activation [29], and with those of Corcoran and Scott, who reported that cholesterol or specific oxysterols are required for Shh signal transduction in medulloblastoma cells and that these sterols would act at the level of Smo [18]. This evidence concerns the gene SHH and medulloblastoma.