Optic Nerve Dysfunction in a Mouse Model of Neurofibromatosis-1 Optic Glioma

Individuals with neurofibromatosis type 1 (NF1) are prone to develop optic pathway gliomas that can result in significant visual impairment. To explore the cellular basis for the reduced visual function resulting from optic glioma fort-nation, we used a genetically engineered mouse model of Nf1 optic glioma (Nf1+/-(CKO)-C-GFAP mice). We performed multimodal functional and structural analyses both before and after the appearance of macroscopic tumors. At 6 weeks of age, before obvious glioma formation, Nf1+/-(CKO)-C-GFAP mice had decreased visual-evoked potential amplitudes and increased optic nerve axon calibers. By 3 months of age, Nf1+/-(CKO)-C-GFAP mice exhibited pronounced optic nerve axonopathy and apoptosis of neurons in the retinal ganglion cell layer. Magnetic resonance diffusion tensor imaging showed a progressive increase in radial diffusivity between 6 weeks and 6 months of age in the optic nerve proximal to the tumor indicating ongoing deterioration of axons. These data suggest that optic glioma formation results in early axonal disorganization and damage, which culminates in retinal ganglion cell death. Collectively, this study shows that Nf1+/-(CKO)-C-GFAP mice can provide a useful model for defining mechanisms of visual abnormalities in children with NF1 and lay the foundations for future interventional studies aimed at reducing visual loss.