d-Aspartate and d-aspartate oxidase show selective and developmentally dynamic localization in mouse retina

d-Enantiomer amino acids, endogenously synthesized and degraded in mammals, participate in multiple developmental and physiological processes. We characterize both d-aspartate and its degradative enzyme (d-aspartate oxidase) in post-natal mouse retina. d-Aspartate attains a developmental peak of 886 nmol/g dry weight at 1-2 weeks post-natal while l-aspartate transiently declines, consistent with the de novo synthesis of d-aspartate. d-Aspartate is localized in many cell-types in different retinal layers, with a notable shift from outer retina to inner retina with time. d-Aspartate oxidase is localized to horizontal cells by in situ hybridization, immunohistochemistry, and histochemical staining methods. Given that final cell specification, differentiation, and synaptogenesis occur during the immediate 2-week post-natal period in the rodent retina and the dynamic appearance of d-aspartate and d-aspartate oxidase, we propose that d-aspartate plays a role in mammalian retinal development.