DISPERSION PATTERNS OF RETINAL NEUROBLASTS

这项研究计划将确定神经母细胞的方式， 不同的层状和功能性命运分散在视网膜内。 携带细菌lacZ基因插入X染色体的转基因小鼠 染色体将被使用，X染色体的自然随机现象 在半合子雌性中的失活将限制 一半的视网膜神经元。由于X染色体失活 在任何视网膜神经母细胞出生之前， 继承了它们祖先的X-活性状态，这种方法允许 大量视网膜克隆的标记。嵌合小鼠，形成 通过将表达lacZ的胚胎细胞与野生型胚胎结合， 也将用于标记少量的视网膜克隆， 证实了X-失活转基因嵌合体小鼠的结果。 来自转基因和嵌合体成年小鼠的视网膜显示出明显的 这种细胞克隆的柱状排列，但也表明， 不同类型的视网膜细胞不尊重这种柱状细胞， 种族隔离克隆相关细胞的分布表明 从大脑皮层的生发区的成神经细胞的分布模式 发育中的视网膜可以包括切向和径向 分量，但切向分量的表达式是 局限于视网膜成神经细胞的不同亚群。本 调查将检验两个假设，这种切线 分散体第一，是由于无源辐射引起的切向色散， 这些细胞作为视网膜细胞的其余部分的移位 扩散？第二，是由于一个活跃的切向色散， 有丝分裂后神经母细胞的移位，在有丝分裂后神经母细胞的分化中发挥作用。 建立特定神经元之间的有序间隔 上课？将检查成人和发育中的视网膜，其中 出生日期相同的视网膜细胞群 在胚胎发生过程中标记。不同类型的视网膜细胞将被B 使用免疫细胞化学鉴定以关联表型， 细胞间距与切向分散程度。这些 研究将阐明产生这种现象的机制， 成熟的视网膜结构。

This research proposal will define the ways in which neuroblasts of distinct laminar and functional fate disperse within the retina. Transgenic mice carrying the bacterial lacZ gene inserted on the X chromosome will be used, and the natural, random phenomenon of X inactivation in hemizygous females will restrict expression of the transgene to half of all retinal neurons. Since X inactivation occurs before any retinal neuroblasts have been born, and because progeny inherit the X-active status of their progenitors, this approach permits the marking of large numbers of retinal clones. Chimeric mice, formed by combining lacZ-expressing embryonic cells with wild-type embryos, will also be used to label small numbers of retinal clones in order to confirm the results from the X-inactivation transgenic mosaic mice. Retinae from both transgenic and chimeric adult mice show a conspicuous columnar arrangement of such clones of cells, but also reveal that distinct types of retinal cell do not respect this columnar segregation. The distributions of the clonally related cells suggest that the dispersion pattern of a neuroblast from the germinal zone of the developing retina can include a tangential as well as a radial component, but that the expression of the tangential component is confined to distinct subsets of retinal neuroblast. The present investigation will examine two hypotheses for this tangential dispersion. First, is tangential dispersion due to a passive displacement of these cells as the remainder of the retinal cells proliferate? And second, is the tangential dispersion due to an active displacement of the postmitotic neuroblasts, playing a role in the establishment of the orderly spacing between neurons of particular classes? Adult and developing retinae will be examined, in which cohorts of retinal cells sharing common birthdates will have been labelled during embryogenesis. Distinct types of retinal cells will b identified using immunocytochemistry to correlate phenotype and intercellular spacing with extent of tangential dispersion. These studies will clarify the mechanisms underlying the creation of the mature retinal architecture.