The Role of Fzd9 in Hippocampal and Cortical Development

描述（由申请人提供）：Frizzled9是一个Wnt受体基因，在人类威廉姆斯综合征的染色体缺失区间内。这种疾病的症状包括视觉空间处理缺陷和癫痫发作的高发生率。Pleasure实验室最近的研究表明，Frizzled9基因突变的老鼠在齿状回有发育缺陷，包括细胞过度死亡，导致齿状颗粒神经元数量小幅减少。这些小鼠也有严重的视觉空间学习缺陷和较低的癫痫发作阈值，模仿威廉姆斯综合征患者的症状；因此，Frizzled9的功能似乎在这种综合征中起着关键作用。wnt在调节树突、轴突和突触形态中发挥重要作用，Fzd9在海马和后皮层中表达。因此，Fzd9转基因小鼠可能具有比已经证明的更广泛的缺陷。目前的研究计划将建立在先前对Fzd9功能的研究基础上，致力于回答三个问题：1。Frizzled9是否调节海马和皮质解剖？2. Frizzled9在成人大脑中有功能吗？和3。典型Wnt信号是否调节齿状回未成熟神经元的形态分化或存活？为了实现这些目标，我将检查Fzd9突变体中详细的细胞神经解剖学和海马体和新皮层的连通性。此外，我将生成条件功能丧失和功能获得突变体，以检查Fzd9在发育和成年期间的作用。这可能表明，突变小鼠成年后重新表达Fzd9可以挽救由于发育过程中Fzd9功能丧失而导致的一些行为缺陷。最后，我将研究Wnt过表达的影响，以更好地了解其在神经发育中的作用。Frizzled9是威廉姆斯综合征中大约20个缺失基因之一；因此，了解其功能对于辨别其在这种情况下的作用至关重要。这种神经发育障碍的特点是友好、热情的个性、语言能力增强和空间认知受损。由于在许多方面，这些患者中保存最完好的功能正是自闭症患者中受损最严重的功能，一些人认为，自闭症患者可能从另一种重要的神经发育综合征中吸取重要的教训。这些研究将有助于我们进一步了解这两种重要的发育障碍。

DESCRIPTION (provided by applicant): Frizzled9, a Wnt receptor gene, is within the chromosomal deletion interval for Williams syndrome in humans. Symptoms of this disease include visuospatial processing defects and a high incidence of seizures. Work from the Pleasure laboratory has recently demonstrated that mice with mutations in Frizzled9 have developmental defects in the dentate gyrus, including excess cell death that result in a small decrease in the number of dentate granule neurons. These mice also have profound visualspatial learning deficits and lowered seizure threshold, mimicking symptoms of Williams Syndrome patients; hence, it seems likely that Frizzled9 function is critical in this syndrome. Wnts have important roles in regulating dendritic, axonal, and synaptic morphology, and Fzd9 is expressed throughout the hippocampus and posterior neocortex. Hence, Fzd9 transgenic mice may have more widespread defects than has already been demonstrated. The current research proposal will build on the previous studies of Fzd9 function by working toward answering three questions: 1. Does Frizzled9 regulate hippocampal and cortical anatomy? 2. Does Frizzled9 have functions in the adult brain? and 3. Does canonical Wnt signaling regulate the morphological differentiation or survival of immature neurons in the dentate gyrus? To accomplish these goal I will examine the detailed cellular neuroanatomy and connectivity of the hippocampus and neocortex in Fzd9 mutants. In addition, I will generate conditional loss-of-function and gain-of-function mutants to examine the role of Fzd9 during development and in adulthood. This may demonstrate that adult re-expression of Fzd9 in mutant mice can rescue some of the behavioral deficits due to a loss of Fzd9 function during development. Finally, I will investigate the effects of Wnt overexpression to better understand its role in neurodevelopment. Frizzled9 is one of approximately 20 genes deleted in Williams syndrome; therefore, understanding its function is critical to discerning its role in this condition. This neurodevelopmental disorder is characterized by a friendly, effusive personality, enhanced language ability and impaired spatial cognition. Since in many ways the most preserved functions in these patients are the exact ones most impaired in autistic patients, some have suggested that there are likely to be important lessons for autism to be learned from this other important neurodevelopmental syndrome. These studies will help to further our understanding of both of these significant developmental disorders.