Fig. 5

Glycam1 is partially responsible for radiation therapy in glaucoma. Optic nerves are robustly protected in wild-type D2 eyes that have undergone radiation-therapy (RAD); however, this protection is less in mice carrying a null allele of Glycam1. D2.Glycam1 ^−/− mice show significantly increased levels of optic nerve degeneration (as assessed by a sensitive PPD stain, a and examples in b) following radiation therapy (n > 50/group). This was most pronounced for the 10.5-month time-point. Since somal and axon degeneration can occur independently, we determined if retinal ganglion cells from D2.Glycam1 ^−/− mice had degenerated within the retina (as opposed to just axon segments within the optic nerve having degenerated). Retinas were sectioned and Nissl stained (n = 4/group) (c) or flatmounted and stained with an antibody against RBPMS (a specific marker of retinal ganglion cells) and with DAPI to counterstain all cells within the inner retina (including amacrine cells, astrocytes, and microglia, as well as retinal ganglion cells [69]) (n = 8 representative counted regions per retina (as in [28]) from 6 eyes/group) (d, e). In wild-type, untreated mice, there is widespread loss of retinal ganglion cells at 12 months of age, and this was prevented in radiation-treated controls. Non-irradiated D2.Glycam1 ^−/− mice had a similar pattern and degree of retinal ganglion cell loss as wild-type controls. The protective benefit of radiation treatment was diminished in D2.Glycam1 ^−/− mice with more mice developing severe optic nerve damage. (Example retinas from eyes with severe optic nerve damage are shown in correspondence to wild-type radiation-treated controls (bottom left panels in b–d).) Thus, the radiation-induced protection from neural damage and the extravastation of monocytes in glaucoma is at least partially dependent on Glycam1. Importantly, non-irradiated (non-RAD) D2.Glycam1 ^−/− mice do not have an increased incidence of glaucomatous neurodegeneration. Thus, Glycam1’s role in lessening glaucoma is context dependent on radiation therapy. Scale bars; RBPMS = 20 μm (a), Nissl = 20 μm (b), PPD = 20 μm (c), **P < 0.01 (d), *P < 0.05, ***P < 0.001. ns non-significant (a Fisher’s exact test; e Student’s t test)