The study of the RAS/RAF/MEK/ERK pathway in children with brain tumors and neurofibromatosis type I (NF-1), where the germline mutation affects NF1, a tumor suppressor gene that acts as a negative regulator for RAS, showed how a defect in the activation of RAS may determine the development of low-grade glioma. The gene discussed is NF1; the disease is neoplasm.