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K.J. Wahlin, N. Yu, R. Adler; Developmental Expression of Synaptic Molecules in the Chick Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):571.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Lack of synapse formation between graft and host remains a major limiting factor for transplantation approaches to the treatment of blinding retinal degenerations. Overcoming this limitation would require recapitulating, in the transplantation setting, the mechanisms of photoreceptor synaptogenesis in the embryo, a process that remains to be elucidated. Towards this goal, we have begun the analysis of synaptogenic molecules expressed in the developing retina in general, and in the outer plexiform layer (OPL) in particular. Methods: Retinas isolated at daily intervals between embryonic day 5 (ED5) and ED20 were either lysed for RNA isolation and cDNA synthesis, or fixed for histological sectioning. Semi–quantitative PCR, immunocytochemistry (ICC), in situ hybridization (ISH) and confocal microscopy were used to investigate expression patterns of 14 pre– synaptic (e.g., syntaxin, CSP–1, etc.), 3 post– synaptic (e.g. homer1–3) and 30 cell interaction molecules (e.g., neurexin, neuroligin, etc.). Results:All of these candidate molecules, selected for analysis based on their localization at synapses or a role in synaptogenesis in other CNS tissues, were expressed in the embryonic retina in at least two different temporal patterns. Several pre–synaptic, post–synaptic and cell interaction molecules were detected at early developmental stages, preceding the reported onset of retinal synaptogenesis. Other molecules appeared much later, at stages corresponding to the time of synaptogenesis in the OPL. Interestingly, several molecules exhibiting this pattern were strongly expressed by photoreceptors. Molecular constituents typical of ribbon synapses were frequently detected prior to the morphological organization of the synapses (e.g., CSP–1). Conclusions: Molecules known to regulate synaptogenesis in other parts of the CNS have now been identified in the developing chick retina. These studies lay the foundation for gain– and loss–of–function studies aimed at identifying the role of these molecules in synapse formation.
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