Significant protection of RGCs has also been demonstrated in diverse animal models of optic neuropathies after intraocular administration of various NTFs, such as ciliary neurotrophic factor (CNTF), glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF) and others. The gene discussed is GDNF; the disease is optic nerve disorder.