For example, the Cre-lox system was employed to generate mice with bi-allelic loss of Nf1 in a specific cell lineage (e.g., astrocyte, Schwann cell), and double mutant Nf1/Tp53 mice were developed to study malignant peripheral nerve sheath tumors and astrocytomas. The gene discussed is NF1; the disease is astrocytoma (excluding glioblastoma).