Holt C E, Bertsch T W, Ellis H M, Harris W A
Department of Biology, University of California at San Diego, La Jolla 92093.
Neuron. 1988 Mar;1(1):15-26. doi: 10.1016/0896-6273(88)90205-x.
Xenopus embryos injected with tritiated thymidine throughout the stages of embryonic retinal neurogenesis showed that more than 95% of the embryonic retinal cells are born within a 25 hr period. While there are shallow central to peripheral, dorsal to ventral, and interlaminar gradients of neurogenesis in these eyes, throughout most of this 25 hr period, postmitotic cells are being added to all sectors and layers. Small clones of differentiated retinal neurons and glia derived from single neuroepithelial cells injected with HRP. These clones were elongated radially. They were also composed of many different combinations of cell types, suggesting a mechanism whereby determination is arbitrarily and independently assigned to postmitotic cells. Such a model, when tested statistically, fits our data very well. We present a scheme for cellular determination in the Xenopus retina in which a coherent group of clonally related cells stretch out radially as lamination begins. This brings different cells into different microenvironments. Local interactions in these microenvironments then lead the cells toward specific fates.
在胚胎视网膜神经发生的各个阶段注射了氚标记胸腺嘧啶核苷的非洲爪蟾胚胎显示，超过95%的胚胎视网膜细胞在25小时内生成。虽然这些眼睛中存在从中央到周边、从背侧到腹侧以及层间的神经发生浅梯度，但在这25小时的大部分时间里，有丝分裂后细胞被添加到所有区域和层。从注射了辣根过氧化物酶（HRP）的单个神经上皮细胞衍生出分化的视网膜神经元和神经胶质细胞的小克隆。这些克隆呈放射状伸长。它们还由许多不同的细胞类型组合组成，这表明有一种机制，通过该机制，分化是随机且独立地赋予有丝分裂后细胞的。当进行统计测试时，这样一个模型与我们的数据非常吻合。我们提出了一个非洲爪蟾视网膜细胞分化的方案，其中一组克隆相关的细胞在分层开始时呈放射状伸展。这将不同的细胞带入不同的微环境。这些微环境中的局部相互作用随后引导细胞走向特定的命运。
