In contrast to mice with other NF1 patient germline NF1 gene mutations, mice with the Arg1809Cys mutation, like NF1 patients with this mutation, do not form pNFs or OPGs and their DRGs and RGCs, respectively, do not exhibit the RAS-independent neuronal hyperexcitability seen in tumor-forming Nf1-mutant central and peripheral nervous system neurons. The gene discussed is NF1; the disease is neoplasm.