Hendrickson A E
Department of Biological Structure, University of Washington, Seattle 98195, USA.
Perspect Dev Neurobiol. 1996;3(3):195-201.
New and existing data are presented regarding synaptic development in primate retina with the aims to identify the sequence in which individual cell types form synapses in the inner plexiform (IPL) and outer plexiform (OPL) layers; to compare synaptic development sequences in cone-dominated fovea and rod-dominated peripheral retina; to compare synaptic formation with other aspects of cell differentiation; and to explore the possible roles for synapses in development. The first synapses are formed in the foveal IPL by bipolar axons at fetal day 55, followed at fetal day 60 by cone ribbon synapses. Amacrine synapses in the foveal IPL only appear in significant numbers at fetal day 88. In peripheral retina amacrine synapses are formed at fetal day 78, bipolar at 99, and photoreceptors at 105. Thus, the fovea forms the first synapses and the IPL matures before the OPL across the retina, but the fovea has a different bipolar/amacrine sequence than peripheral retina. Foveal synapses are present before many photoreceptor-specific proteins such as opsins can be detected, suggesting that some phenotypic information from the inner retina could influence the direction of photoreceptor development. The early synaptic development in the fovea may serve an important mechanical role during subsequent cell migrations that form the mature foveal pit and tightly packed cone foveola.
本文展示了有关灵长类动物视网膜突触发育的新数据和现有数据，目的是确定不同细胞类型在视网膜内网状层（IPL）和外网状层（OPL）形成突触的顺序；比较在以视锥细胞为主的中央凹和以视杆细胞为主的周边视网膜中的突触发育顺序；将突触形成与细胞分化的其他方面进行比较；并探讨突触在发育过程中的可能作用。最早的突触在胚胎第55天时由双极轴突在中央凹的IPL中形成，随后在胚胎第60天时出现视锥细胞的带状突触。中央凹IPL中的无长突细胞突触在胚胎第88天时才大量出现。在周边视网膜中，无长突细胞突触在胚胎第78天时形成，双极细胞突触在第99天时形成，光感受器突触在第105天时形成。因此，中央凹形成最早的突触，并且在整个视网膜中IPL比OPL先成熟，但中央凹的双极细胞/无长突细胞顺序与周边视网膜不同。在许多光感受器特异性蛋白（如视蛋白）能够被检测到之前，中央凹的突触就已存在，这表明来自内视网膜的一些表型信息可能会影响光感受器发育的方向。中央凹早期的突触发育可能在随后形成成熟中央凹坑和紧密排列视锥小凹的细胞迁移过程中发挥重要的机械作用。
