NF1 and neurocutaneous syndrome: NF1 is a frequent neurocutaneous syndrome which easily causes various benign or malignant tumors.57 To identify a NF1 specific target drug, CRISPR/Cas9 was used to develop different cell lines, NF1 wild type (NF1+/+), NF1 heterozygous (NF1+/−), and NF1 homozygous (NF1−/−).