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层区域图（皮层的基本功能组织）形成的机制。这些发现对于理解各种各样的皮质出生缺陷和源于早期皮质异常的迟发性疾病具有重要意义。我在这里建议继续一个富有成效的研究路线，在我的研究小组发现，分泌的信号分子FGF 8调节图案的皮质区地图沿着前/后（A/P）轴的皮质原基。这项建议有三个目的。第一个目的是更好地理解A/P图案化信号。目前，我们还不知道FGF 8和同一FGF亚家族的成员是否形成了一个信号梯度，将位置值传递给皮层，或者它们是否触发了其他模式机制的中继。使用小鼠遗传学，我们将产生具有逐渐降低的FGF 8亚家族配体水平的小鼠，以确定皮质区域图是否显示增加的变化。如果是这样的话，这将为梯度模型提供支持，而不考虑最简单的中继模型。为了确定哪些FGF受体传递图案化信号，将分析缺乏FGF受体组合的小鼠，以确定它们的皮质图谱是否显示出类似于FGF 8缺乏的缺陷。由于FGF/FGFR结合需要硫酸乙酰肝素（HS），我们将评估大脑皮质中缺乏HS的小鼠的皮质区域图。虽然其他生长因子需要HS，但我们想知道FGF信号传导的丧失将如何影响区域模式。地图是同质化的，还是默认的模式？在目标2中，我们将使用显性阴性FGFR的子宫内电穿孔来确定皮质细胞是否在远离FGF 8源的距离处检测到FGF信号传导水平，并且当这些水平改变时，通过采用新的区域命运来响应。我们还将通过电穿孔引入FGF 8的第二来源，并确定多个区域是否重复，如果是，是否以及如何沿着次级A/P轴对重复图进行排序。在目标3中，我们将测试的假设，FGF信号也参与了端脑到背侧大脑皮层和基底前脑的核的初级分裂。我们将使用小鼠遗传学，在子宫内电穿孔，并试图拯救小鼠突变体与过量的FGF测试是否FGF信号抑制皮质的命运，促进腹侧端脑的命运。

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.