NF1 and neurofibromatosis type 1: Recently, Zhu et al. [33] found that mice genetically engineered to lack the neurofibromatosis-1 tumor suppressor gene demonstrated a variety of developmental defects that resulted in increased proliferation of glial progenitors cells, which in some cases led to optic nerve glioma formation (part of the neurofibromatosis-1 neoplasia phenotype).