Retinal Thy-1 expression during development.

PURPOSE To evaluate the developmental expression of Thy-1 in the retina. Thy-1, the most abundant mammalian neuronal surface glycoprotein, is likely to play a significant role in retinal development. In the mammalian retina, it is found predominantly, if not exclusively, on retinal ganglion cells. METHODS Rat retinae of various ages were stained immunohistochemically for Thy-1 with 2G12, a monoclonal Thy-1 antibody. Sections were analyzed digitally to quantify bound antibody. Using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), the expression of Thy-1 protein was compared with the levels of mRNA detected. RESULTS Thy-1-dependent fluorescence was detected in rat retinae from birth, albeit at low levels. Thy-1 labeling was localized predominantly to the ganglion cell layer. Minimal, fine patterns of linear and reticular fluorescence were noted in the inner nuclear layer. Thy-1 levels reached a maximal level at approximately postnatal day 14. RT-PCR measurements showed a similar time course for the increase in Thy-1 expression. CONCLUSIONS The Thy-1 antigen is present in the inner retina at birth. Its level increases steadily after birth and peaks during the second week of life. Thy-1 expression is approximately coterminous with synaptogenesis of the inner plexiform layer and may play a role in synaptogenesis of the inner retina or in other developmental milestones in the formation of the visual system.