Molecular Mechanisms of Cerebral Cortical Patterning

描述（由申请人提供）：我的长期目标是了解启动哺乳动物大脑皮层发育并控制皮质区域图（皮质的基本功能组织）形成的机制。研究结果应该有助于了解各种皮质出生缺陷以及由早期皮质异常引起的后期发病的疾病。我在此建议继续开展一系列卓有成效的研究，其中我的研究小组发现，分泌的信号分子 FGF8 沿着皮质原基的前/后 (A/P) 轴调节皮质区域图的模式。该提案有三个目标。第一个目标是更好地理解 A/P 模式信号。目前我们不知道 FGF8 和同一 FGF 亚家族的成员是否形成信号梯度以向皮质传递位置值，或者它们是否触发其他模式机制的中继。利用小鼠遗传学，我们将产生 FGF8 亚家族配体水平逐渐降低的小鼠，以确定皮质区域图是否显示增加的变化。如果是这样，这将为梯度模型提供支持，并折扣最简单的中继模型。为了确定哪些 FGF 受体传递模式信号，将对缺乏 FGF 受体组合的小鼠进行分析，以确定它们的皮质图是否显示出类似于 FGF8 缺陷的缺陷。由于 FGF/FGFR 结合需要硫酸乙酰肝素 (HS)，因此我们将评估大脑皮层中缺乏 HS 的小鼠的皮质区域图。尽管其他生长因子需要 HS，但我们想知道 FGF 信号传导的丧失将如何影响区域图案。地图会同质化，还是会出现默认模式？在目标 2 中，我们将使用显性失活 FGFR 的子宫内电穿孔来确定皮质细胞是否在距 FGF8 源一定距离处检测到 FGF 信号传导水平，并且当这些水平发生变化时，通过采用新的区域命运进行响应。我们还将通过电穿孔引入 FGF8 的第二个来源，并确定多个区域是否重复，如果是，则重复的图谱是否以及如何沿辅助 A/P 轴排序。在目标 3 中，我们将检验以下假设：FGF 信号传导也参与端脑初级分裂为背侧大脑皮层和基底前脑核。我们将使用小鼠遗传学，在子宫内电穿孔，并尝试拯救具有过量 FGF 的小鼠突变体，以测试 FGF 信号传导是否抑制皮质命运并促进腹侧端脑命运。

DESCRIPTION (provided by applicant): My long term goal is to understand the mechanisms that initiate development of the mammalian cerebral cortex and control the formation of the cortical area map, the basic functional organization of the cortex. Findings should be relevant to understanding a wide variety of cortical birth defects, and diseases with later onset that stem from early cortical abnormalities. I propose here to continue a fruitful line of research in which my research group found that the secreted signaling molecule FGF8 regulates patterning of the cortical area map along the anterior/posterior (A/P) axis of the cortical primordium. This proposal has three aims. The first aim is to understand the A/P patterning signal better. At present we do not know if FGF8 and members of the same FGF subfamily form a signaling gradient to impart positional values to the cortex, or if they trigger a relay of other patterning mechanisms. Using mouse genetics we will generate mice with progressively lower levels of FGF8 subfamily ligands to determine if the cortical area map shows increasing shifts. If so, this would provide support for a gradient model, and discount the simplest relay model. To determine which FGF receptors relay the patterning signal, mice that lack combinations of FGF receptors will be analyzed to determine if their cortical maps show defects similar to an FGF8 deficiency. Because FGF/FGFR binding requires heparan sulfate (HS), we will evaluate the cortical area map in mice that lack HS in the cerebral cortex. Although other growth factors require HS, we want to know how loss of FGF signaling will affect area patterning. Will the map be homogenized, or will a default pattern be present? In Aim 2 we will use in utero electroporation of dominant negative FGFRs to determine if cortical cells detect levels of FGF signaling at a distance from the FGF8 source, and, when these levels change, respond by adopting a new area fate. We will also introduce a second source of FGF8 by electroporation and determine if multiple areas are duplicated, and if so, whether and how duplicate maps are ordered along a secondary A/P axis. In Aim 3, we will test the hypothesis that FGF signaling is also involved in the primary division of the telencephalon into the dorsal cerebral cortex and the nuclei of the basal forebrain. We will use mouse genetics, in utero electroporation, and attempted rescue of mouse mutants with excess FGFs to test whether FGF signaling suppresses the cortical fate and promotes ventral telencephalic fates.