Mice generated with CRISPR-based in utero electroporation of three deleted genes encoding phosphatase and tensin homolog (Pten), neurofibromin 1 (Nf1), and p53 (Trp53), all linked to tumorigenesis in human glioma genes, show a brain tumor with progressive cortical hyperexcitability due to tumor invasion and spontaneous seizures. The gene discussed is PTEN; the disease is central nervous system cancer.