Early Events in Cortical Development

描述（由申请人提供）：新皮层是大脑皮层中最大的区域，负责处理产生知觉、意志运动反应以及学习和记忆等复杂现象的感觉信息。这些不同的功能由新皮层的专门“区域”执行，其特征是独特的连接和结构。该项目的持续目标是定义和研究指导哺乳动物新皮层的解剖、连接和功能组织的发育机制，并将其划分为不同的区域。新皮质区域的特异和分化可能是由新皮质固有的遗传调控和外在影响（如丘脑皮质（TCA）输入）之间的相互作用控制的，后者传递来自丘脑背侧主要感觉核的感觉信息。最近的一项重大进展是通过对EMX2和PAX6突变体的功能丧失分析（Sey/Sey），证明了涉及转录因子EMX2和PAX6的基因调控。然而，EMX2和PAX6的这种作用只能从用作皮质位置标记的基因的模式表达变化中推断出来，因为这些突变体在P0上死亡，远在该区域在解剖学和功能上被定义之前。TCA输入的作用主要局限于发现在缺乏TCAs的情况下，标记基因的胚胎模式是正常的，由于缺乏TCA的可用突变体在P0时死亡，TCA输入的作用也受到限制。因此，调节实现的机制仍然缺乏特征。我们的目标是定义EMX2和PAX6作为内在调节因子的充充性和需求，TCA输入作为外在影响，我们将使用功能获得（转基因）和功能丧失（条件敲除）分析以及遗传细胞切除来验证我们的假设，在设计为成年的小鼠中使用组织特异性基因激活/失活方法。我们将分析皮层神经元的区域特异性表型，包括位置身份标记的表达，区域特异性输入和输出投影，以及新皮层进入区域的解剖和功能组织。提出的多层次分析和备选战略将避免与更有限的方法有关的潜在问题，提供补充的发现，以证实解释和对实现规则的进一步见解。我们期望发现支持我们的假设，但实验的设计使得反驳我们假设的结果同样具有信息量。

DESCRIPTION (provided by applicant): The neocortex, the largest region of the cerebral cortex, processes sensory information giving rise to perception, volitional motor responses, and to complex phenomena such as learning and memory. These distinct functions are performed by specialized 'areas' of the neocortex, characterized by unique connectivity and architecture. The continuing objective of this project is to define and study developmental mechanisms that direct the anatomical, connectional, and functional organization of the mammalian neocortex, and its parcellation into areas. The specification and differentiation of neocortical areas is likely controlled by interplay between genetic regulation intrinsic to the neocortex and extrinsic influences such as thalamocortical (TCA) input that relays sensory information from the principal sensory nuclei of dorsal thalamus. A major recent advance is evidence for the genetic regulation of arealization that implicates the transcription factors EMX2 and PAX6 by loss of function analysis of mutants for Emx2 and Pax6 (Sey/Sey). However, this role for EMX2 and PAX6 is only inferred from changes in the patterned expression of genes used as positional markers in cortex because these mutants die on P0, well before areas become anatomically and functionally defined. The role of TCA input, which has been mainly limited to the finding that embryonic patterning of marker genes is normal in the absence of TCAs, is also limited because the available mutants that lack TCAs die at P0. Thus, mechanisms regulating arealization remain poorly characterized. Our goal is to define the sufficiency and requirements for EMX2 and PAX6 as intrinsic regulators, TCA input as an extrinsic influence, We will test our hypotheses using gain of function (transgenic) and loss of function (conditional knockouts) analyses, as well as genetic cell ablations, using tissue-specific gene activation / inactivation approaches in mice designed to live to be adults. We will analyze the area-specific phenotypes of cortical neurons, including expression of markers of positional identity, area-specific input and output projections, and the anatomical and functional organization of the neocortex into areas. The multilevel analyses and alternative strategies proposed will circumvent potential problems associated with more limited approaches, provide complementary findings to substantiate interpretations and further insights into the regulation of arealization. We expect findings that support our hypotheses, but the experiments are designed such that results that disprove our hypotheses will be equally informative.