Dräger U C
Proc R Soc Lond B Biol Sci. 1985 Mar 22;224(1234):57-77. doi: 10.1098/rspb.1985.0021.
In the mouse, as in most mammals, the crossed optic projections originate from the entire extent of the retina, whereas ganglion cells giving rise to the uncrossed (ipsilateral) projection are restricted to the temporal and ventral retina. The nasal border of this bilaterally projecting region in the retina corresponds to the midline of the visual field. Here the birth dates of ipsilaterally and contralaterally projecting ganglion cells were determined by combining tritiated thymidine labelling in the embryo with horseradish peroxidase tracings from the optic tract in the adult. Contralaterally projecting ganglion cells were found to be generated from embryonic day E11 to about E19 in a crude concentric fashion with the oldest cells in central and youngest ones in peripheral retina. Ipsilaterally projecting cells were born from E11 to E16, that is, during the earlier part of the period in which the contralateral projection was born. At the earliest time of ganglion cell generation (E11-12) ipsi- and contralaterally projecting cells were born within separate retinal regions, with the future midline representation forming the border between the two zones. This distinction became lost after E13, when both ipsi- and contralaterally projecting cells were born in the bilaterally projecting region. Hence at E11-12 the retina was found to have a bipartite organization that may allow the specification of the two maps of opposite topographical polarity in which the crossed and uncrossed projections are organized. Since in the adult retina this bipartite organization is preserved only in the large ganglion cells that project to the lateral geniculate nucleus, and since large ganglion cells are known to be the earliest ones formed in the mouse, these cells may be the ones that establish the early and bilateral projections of the retina. The conclusion that the bilateral projection system in the retina reflects an early developmental programme, and not the result of competition between the two eyes at later stages, was reinforced by observing a practically normal retinal origin of ipsilateral projections in mice which had only one normal eye from the earliest stages of eye development.
与大多数哺乳动物一样，在小鼠中，交叉性视投射起源于整个视网膜范围，而产生不交叉（同侧）投射的神经节细胞则局限于颞侧和腹侧视网膜。视网膜中这个双侧投射区域的鼻侧边界对应于视野的中线。在此，通过将胚胎期的氚标记胸腺嘧啶核苷标记与成年期视束的辣根过氧化物酶追踪相结合，确定了同侧和对侧投射神经节细胞的出生日期。发现对侧投射神经节细胞在胚胎第11天（E11）至约第19天（E19）以大致同心的方式产生，中央的细胞最老，周边视网膜的细胞最年轻。同侧投射细胞在E11至E16期间产生，即在对侧投射产生时期的较早阶段。在神经节细胞产生的最早时间（E11 - 12），同侧和对侧投射细胞在视网膜的不同区域产生，未来的中线代表区域形成两个区域之间的边界。在E13之后这种区分消失，此时同侧和对侧投射细胞都在双侧投射区域产生。因此，在E11 - 12时发现视网膜具有二分组织，这可能允许确定交叉和不交叉投射所组织的两个具有相反拓扑极性的图谱。由于在成年视网膜中，这种二分组织仅在投射到外侧膝状体核的大神经节细胞中保留，并且由于已知大神经节细胞是小鼠中最早形成的细胞，这些细胞可能是建立视网膜早期双侧投射的细胞。通过观察在眼睛发育最早阶段只有一只正常眼睛的小鼠中同侧投射的视网膜起源实际上正常，进一步证实了视网膜中的双侧投射系统反映了早期发育程序，而不是后期两眼之间竞争的结果这一结论。
