Mouse modeling of neurofibromatosis 1 (NF1) optic pathway glioma: While mice lacking Nf1 in brain astrocytes do not develop glioma, Nf1+/- mice lacking Nf1 expression in astrocytes (GFAPCre; Nf1^flox/mut mice) form optic nerve and chiasm gliomas. The upper panel depicts an enlarged optic nerve and chiasm in one representative GFAPCre; Nf1^flox/mut mouse that correlates with histologic evidence of tumor (bottom panel). These findings support a role for Nf1+/- brain cells in NF1 glioma development. For details, see the article by Bajenaru et al. on p. 8573 of this issue.