For grade I meningiomas, mutations in AKT1 (v-akt murine thymoma viral oncogene homolog 1, leading to activation of the PI3K pathway), TRAF7 (Tumor necrosis factor receptor-associated factor 7, encoding the pro-apoptotic E3 ubiquitin ligase), KLF4 (Krupple-like factor 4, a pluripotency-inducing transcription factor) and SMO (Smoothened, frizzled family receptor, leading to activation of the Hedgehog pathway) have been identified and appear to be mutually exclusive of NF2 alterations (22). The gene discussed is SMO; the disease is meningioma.