Regulation of Forebrain Neurogenesis by the Energy Sensor AMP Kinase

描述（由申请人提供）：哺乳动物皮质发育是一个复杂且受到严格调控的过程。虽然它是已知的，体液和转录调节产生的哺乳动物端脑中的细胞多样性，一个相对未开发的领域是祖细胞群体是否也代谢不同，在何种程度上代谢调节的前体细胞有助于端脑神经发生。AMP活化蛋白激酶（AMPK）是一种能量传感器，在所有真核细胞的能量和氧化还原稳态中起核心作用。近年来的研究表明，AMPK参与了许多重要的生物学过程，包括细胞结构、极性、细胞分裂、迁移以及生物体的正常生长发育。在本申请中，我们将测试我们的假设，AMPK调节神经发生在端脑通过其能量感应功能。AMPK作为催化和调节的异源三聚体存在，亚单位。哺乳动物表达2 <$，2 <$和3？亚单位。对AMPK在神经细胞中的功能知之甚少。在果蝇中的研究表明，AMPK是维持神经前体细胞有丝分裂能力所必需的，AMPK功能的丧失也会导致进行性神经变性。我们的研究（Dev。Cell，2009）在种系突变小鼠中显示大量细胞凋亡，其主要限于产前胚胎中发育端脑的中间祖细胞（IPC及其后代），而在出生后脑中，细胞凋亡限于发育小脑的外部颗粒层。体外分析表明，细胞内在的G2 M特异性缺陷和细胞凋亡的突变神经前体。在这个应用程序中，我们将集中在端脑。在我们最近产生的条件性敲除小鼠和其他转基因小鼠的帮助下，我们将进行生物能量学研究，以检查背侧和腹侧端脑IPC的代谢独特性是否使它们在增殖，存活，迁移和分化（Aim 1）期间对AMPK功能的丧失更敏感。我们将通过使用区域特异性Cre系来降低<$1功能（Aim 2），在体内研究<$1在端脑背侧和腹侧对神经发生的区域控制。在Aim 3中，我们将使用三种尖端技术来研究体内完整大脑中特定区域的组织生物能量学和代谢组学。我们希望我们的研究将提供新的层面，我们的理解皮质发育的光细胞代谢。新的AMPK效应子和AMPK亚基特异性小分子调节剂的鉴定可能有一天会导致神经退行性和代谢性疾病的新疗法。 公共卫生相关性：AMPK是CNS中葡萄糖敏感和营养代谢的重要介质。大脑中不适当的AMPK激活会导致有害影响。由于快速发育的大脑容易受到营养缺乏或过量的影响，妊娠糖尿病或营养不良（导致出生缺陷和记忆缺陷）可能会引发胎儿中AMPK的不当激活。这可能导致胎儿大脑皮质畸形和发育缺陷，以及儿童认知缺陷。因此，AMPK调节药物可能对胎儿皮质生成有直接影响。事实上，广泛使用的二甲双胍治疗2型糖尿病的一种机制是通过其对AMPK的作用。然而，二甲双胍是否对胎脑中AMPK活化有任何直接影响尚不清楚。了解AMPK的亚基特异性功能将导致对开发AMPK异源三聚体特异性AMPK调节剂的兴趣。此外，我们对AMPK 1突变小鼠的初步研究显示，产生中间神经元的IPC优先丢失。了解调节中间神经元产生和迁移的机制是重要的，因为灵长类动物大脑的复杂性归因于这些祖细胞的大量增殖，并且有缺陷的中间神经元发育和迁移与各种神经系统疾病如精神分裂症，癫痫和无脑畸形相关。我们的研究将在鉴定新型AMPK亚基特异性小分子调节剂方面开辟令人兴奋的新研究途径，这可能会导致神经退行性疾病和代谢疾病的新疗法。

DESCRIPTION (provided by applicant): Mammalian cortical development is a complex and tightly regulated process. While it is known that humoral and transcriptional regulation generates the cellular diversity in the mammalian telencephalon, a relatively unexplored area is whether the progenitor populations are also metabolically distinct and the extent to which metabolic regulation of precursor cells contribute to neurogenesis in the telencephalon. AMP- activated protein kinase (AMPK) is an energy sensor and plays a central role in energy and redox homeostasis in all eukaryotic cells. Recent studies show, that AMPK controls many fundamental processes including regulation of cell structures, polarity, cell division, migration and normal growth and development of organisms. In this application we will test our hypothesis that AMPK regulates neurogenesis in the telencephalon though its energy sensing functions. AMPK exists as a heterotrimer of catalytic ¿ and regulatory ¿ and ? subunits. Mammals express 2¿, 2¿ and 3? subunits. Not much is known about AMPK function in neural cells. Studies in Drosophila demonstrate that AMPK is necessary for maintaining mitotic competence of neural precursors and loss of AMPK function also causes progressive neurodegeneration. Our published study (Dev. Cell, 2009) in the germline ¿1 mutant mice shows massive apoptosis, which was primarily restricted to the intermediate progenitors (IPCs and their progeny) of developing telencephalon in the prenatal embryo, while in the postnatal brain apoptosis was restricted to the external granule layer of the developing cerebellum. In vitro analysis showed cell-intrinsic G2M-specific defects and apoptosis of ¿1 mutant neural precursors. In this application, we will focus on the telencephalon. With the help of our recently generated ¿1 conditional knockout mouse and other transgenic mice, we will conduct bioenergetics studies to examine whether metabolic uniqueness of dorsal and ventral telencephalon IPCs render them more sensitive to loss of AMPK function during their proliferation, survival, migration and differentiation (Aim1). We will examine regional control of neurogenesis by ¿1 in the dorsal and ventral telencephalon in vivo, by using region-specific Cre lines to reduce ¿1 function (Aim2). In Aim3, we will use three cutting edge technologies to investigate region-specific tissue bioenergetics and metabolomics in the intact brain in vivo. We expect that our studies will provide new dimensions to our understanding of cortical development in the light of cellular metabolism. Identification of novel AMPK effectors and AMPK subunit-specific small molecule modulators could one day potentially lead to novel therapeutics for neurodegenerative and metabolic diseases. PUBLIC HEALTH RELEVANCE: AMPK is an important mediator of glucose sensing and nutrient metabolism in the CNS. Inappropriate AMPK activation in the brain causes deleterious effects. Because the rapidly developing brain is vulnerable to nutrient deficiency or overabundance, gestational diabetes or malnutrition (that cause birth defects and memory deficits), is likely to trigger improper AMPK activation in the fetus. This could lead to cortical malformations and developmental defects in the fetal brain and cognitive deficits in children. Thus, AMPK modulating drugs could have a direct effect on fetal corticogenesis. In fact, one mechanism by which the widely prescribed drug metformin works in Type2 diabetes is by its action on AMPK. Little is known however, whether metformin has any direct effect on AMPK activation in the fetal brain. Understanding the subunit-specific functions of AMPK would lead to interest in developing AMPK heterotrimer-specific AMPK modulators. Moreover, our preliminary studies in the AMPK¿1 mutant mouse show preferential loss of IPCs that give rise to interneurons. Understanding the mechanisms that regulate interneuron generation and migration is important as the complexity of the primate brain is attributed to the massive proliferation of these progenitors and defective interneuron development and migration is correlated with various neurological disorders like schizophrenia, epilepsy and lissencephaly. Our studies will open exciting new avenues of research in identification of novel AMPK subunit-specific small molecule modulators which could potentially lead to novel therapeutics for neurodegenerative and metabolic diseases.