MAPK9 and ocular hypertension: It is unclear if the involvement of JNK1 specific to D2 glaucoma is the result of the differing nature of the insult (progressive, chronic ocular hypertension compared with acute and sudden mechanical axonal injury), the potential for ocular hypertension to directly perturb pathways in more than just RGC axons, the involvement of other cells besides RGCs, or the absence of JNK2 and 3.