Capitalizing on the high tumor penetrance, stereotypic tumor location (prechiasmatic optic nerve and chiasm), and well-defined temporal course of optic glioma development in GEM [19, 55], we employed several different Nf1-mutant mouse lines and two complementary experimental approaches to demonstrate that brain injury establishes a supportive microenvironment sufficient for optic glioma formation in mice with progenitor cell Nf1 loss. This evidence concerns the gene NF1 and neoplasm.