Genetic Specification Of Thalamocortical Projections

描述(由申请人提供)：每个丘脑核团到一组独特的皮质区域的地形投影是描述每个感觉通道的输入特异性的基础。尽管丘脑皮质投射的模式对正常大脑功能的重要性早已被认识到，但其潜在的发育机制在很大程度上仍不清楚。该项目的目的是确定哺乳动物丘脑皮质投射的关键分子线索。 我们最近获得的证据表明：(I)存在于中间靶点腹侧端脑的地形图线索，在丘脑皮质投射到不同皮质区域的分类中发挥关键作用，以及(Ii)bHLH转录因子Neurogenin2通过控制存在于腹侧端脑的中间线索的轴突反应性，自主地指定丘脑投射的地形图。在这些初步成果的基础上，将实现以下具体目标： 1.使用一种新的“整体安装”体外实验来确定腹侧端脑在丘脑轴突投射到不同皮质区域的模式中的作用。该方法概括了体内观察到的丘脑轴突投射的一些关键方面。 2.确定神经生长素2在丘脑皮质投射定位中的作用。我们将使用功能增益方法测试在丘脑神经元连通性规范中对Ngn2表达的空间和时间要求，其中全长Ngn2或干扰结构将使用电穿孔介导的基因转移在丘脑背侧异位或异时表达。 3.分离并鉴定发育中丘脑中神经原蛋白2的转录靶点。我们将使用候选方法和无偏见的全基因组方法确定由Ngn2转录控制并参与丘脑轴突投射模式的一组基因。

DESCRIPTION (provided by applicant): The topographic projection of each thalamic nucleus to a unique set of cortical areas underlies the input specificity characterizing each sensory modality. Although the importance of the patterning of thalamocortical projections for normal brain function has long been appreciated, the underlying developmental mechanisms remain largely unknown. The aim of this project is to identify the key molecular cues patterning thalamocortical projections in mammals. We recently obtained evidence demonstrating that (i) topographic cues present in an intermediate target, the ventral telencephalon, play a critical role in the sorting of thalamocortical projections to distinct cortical domains and (ii) that the bHLH transcription factor Neurogenin2 specifies cell-autonomously the topography of thalamic projections by controlling axon responsiveness to the intermediate cues present in the ventral telencephalon. Based on these preliminary results, the following Specific Aims will be carried out: 1. Determine the role of the ventral telencephalon in the patterning of thalamic axons projections to distinct cortical domains using a new 'whole-mount' in vitro assay recapitulating some of the key aspects of the topography of thalamic axon projections observed in vivo. 2. Determine the role of Neurogenin2 in the specification of the topography of thalamocortical projection. We will test the spatial and temporal requirement of Ngn2 expression in the specification of thalamic neurons connectivity using a gain-of-function approach where full-length Ngn2 or interfering constructs will be ectopically or heterochronically expressed in the dorsal thalamus using an electroporation-mediated gene transfer. 3. Isolate and characterize the transcriptional targets of Neurogenin2 in the developing thalamus. We will identify the set of genes controlled transcriptionally by Ngn2 and involved in the patterning of thalamic axon projections using both a candidate approach and an unbiased genome-wide approach.