SPP1 and optic nerve disorder: Notably, a recent study explored a non-neuronal expression of Spp1 in astrocytes under various optic neuropathies and natural aging conditions.27 However, while we did not detect Spp1 expression derived from glial cells in either naive or SOHU conditions, we did observe a highly regulated Spp1 expression specific to RGC neurons (Figures S2D and S2E).