Dispersion Patterns for Retinal Neuroblasts

描述(申请人提供)：视网膜的结构复杂性是由一系列发育事件引起的，这些事件控制着增殖、命运决定、迁移、过程生长、目标识别、突触发生和细胞死亡。这些过程建立了一个精确的分层结构，其中视网膜神经元位于不同的深度，通过两个中间的突触层连接。叠加在这种分层组织之上，某些类型的细胞以有序的阵列分布在给定层上，以便它们及其过程确保在建立与其传入神经元和靶神经元的连接时对视网膜表面进行统一采样。这项研究计划试图了解这种模式的细胞、分子和遗传决定因素以及这种阵列中的连通性，重点是水平细胞的数量。对重组近交系水平细胞数量的定量性状分析将首先确定控制这一神经元群体大小的基因。嵌合小鼠将从水平细胞数量不同的亲本菌株中产生，以确定树突场的大小是否受细胞固有指令和环境指令的控制。还将对视锥感光细胞进行类似的数量性状分析，并将在调节视锥细胞与水平细胞之间的汇聚比例或改变或取消这些传入细胞与树突之间的神经传递的各种敲除和重组近交系中，研究传入细胞在指定水平细胞的树突模式中所起的作用。将确定同型邻居和传入细胞在建立这种连通性中所扮演的角色，以检验这样的假设，即视觉活动的开始推动相邻水平细胞之间的竞争性相互作用，因为它们寻求在发育中的外丛状层定植单个椎弓根。来自两个亲本菌株的胚胎视网膜的微阵列分析显示，水平和锥体细胞数量都有两倍的差异，将被用来识别对建立这些差异至关重要的下游基因。这些实验将揭示调节水平和锥体细胞数量的基因，以及水平细胞在发育过程中建立其形态模式、树突覆盖和与锥体传入细胞的连接的生物学机制。

DESCRIPTION (provided by applicant): The architectural complexity of the retina is brought about by a series of developmental events controlling proliferation, fate determination, migration, process outgrowth, target recognition, synaptogenesis and cell death. These processes establish a precisely layered structure in which retinal neurons become positioned at different depths, connected via two intervening synaptic layers. Superimposed upon this layered organization, certain cell types are distributed as orderly arrays across a given layer so that they, and their processes, ensure a uniform sampling of the retinal surface as they establish connectivity with their afferent and target neurons. This research program is seeking to understand the cellular, molecular and genetic determinants of this patterning and connectivity in such arrays, focusing upon the population of horizontal cells. A quantitative trait analysis of horizontal cell number in recombinant inbred strains will first identify genes that control the size of this neuronal population. Chimeric mice will be produced from parental strains that differ in horizontal cell number, to determine whether dendritic field size is controlled by cell-intrinsic vs. environmental instructions. A comparable quantitative trait analysis of the cone photoreceptors will also be conducted, and the role played by the afferents in specifying dendritic patterning of horizontal cells will be examined in various knockout and recombinant inbred strains in which the convergence ratio between cones and horizontal cells is modulated, or in which neurotransmission between these afferents and the dendrites is altered or abolished. The roles played by both homotypic neighbors and by afferents in the establishment of this connectivity will be determined, examining the hypothesis that the onset of visual activity drives a competitive interaction between neighboring horizontal cells as they seek to colonize individual pedicles in the developing outer plexiform layer. Microarray analysis of embryonic retina from two parental strains showing a two-fold difference in both horizontal and cone cell number will be used to identify downstream genes critical for the establishment of these differences. These experiments will reveal the genes that regulate horizontal and cone cell number, as well as the biological mechanisms by which horizontal cells establish their morphological patterning, dendritic coverage and connectivity with cone afferents during development.