Hypothalamic-pituitary-adrenal function Fragile X mouse

下丘脑-垂体-肾上腺功能脆性X小鼠

• 批准号: 7023445
• 负责人: JULIE C LAUTERBORN
• 金额: $ 7.63万
• 依托单位: UNIVERSITY OF CALIFORNIA-IRVINE
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-10 至 2008-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7023445
• 关键词: adrenocorticotropic hormone; anxiety; behavioral /social science research tag; corticosteroid receptors; corticosterone; corticotropin releasing factor; cortisol; developmental disease /disorder; developmental genetics; disease /disorder model; fragile X syndromes; genetically modified animals; glutamate receptor; hormone regulation /control mechanism; hypothalamic pituitary adrenal axis; immature animal; immunocytochemistry; laboratory mouse; mature animal; neurogenetics; neurotransmitter antagonist; stress; tissue /cell culture; western blottings

DESCRIPTION (provided by applicant): Fragile X syndrome (fraX), resulting from the loss of fragile X mental retardation protein (FMRP), is the most common cause of inheritable mental retardation. In addition to cognitive impairment, fraX is characterized by abnormal "stress-related" behaviors, and children with fraX have greater basal and stress-induced salivary levels of the adrenal hormone cortisol, as compared to unaffected siblings. These data suggest that hypothalamic-pituitary-adrenal (HPA) axis function is altered in fraX. A murine model of fraX has been developed that exhibits several features of this syndrome and holds promise for identifying the cellular and behavioral consequences of Fmr1 deletion. Work by the investigator has demonstrated that fragile X mental retardation 1 gene knockout (Fmr1-K0) mice also have greater responses to stress including elevated gene expression and glucocorticoid levels than do wild-type mice. These data indicate that Fmr1-KOs are exhibiting a hyper-stress response, similar to the phenotype in human fraX, yet more information is needed as to the extent the HPA axis is altered, the cellular basis of this dysfunction, and potential therapeutic targets. The goal of the proposed research is to obtain such information and lay the groundwork for understanding the contribution of an exaggerated stress response to cognitive impairment in fraX. Three aims are proposed. Specific Aim 1 will test the hypothesis that there is a generalized increase in HPA tone in fragile X mutants (Aims 1A & 1B), and that the disparity among genotypes is enhanced by chronic stress (Aim 1A). In Aim 1A, adrenocorticotropic hormone (ACTH) release and corticotropin-releasing factor receptor 1 (CRH-R1) mRNA levels will be analyzed at three ages (3 mo, 12 mo, 24 mo) in handled (unstressed) and stressed Fmr1-KO and WT mice. Aim 1B will examine basal, diurnal corticosterone fluctuations in Fmr1-KOs and WTs to determine if levels are altered as in fraX humans. Specific Aim 2 will test the hypothesis that immobilization stress will alter the subcellular compartmentalization of the glucocorticoid receptor in fraX mutants as compared to WT mice (Aim 2A) at the light microscopic level and, in particular, that there are greater levels of glucocorticoid receptor in nuclear fractions of cortical cells from Fmr1-KOs as compared to WTs under basal conditions and following stress (2B) using Western blot analysis. Specific Aim 3 will test the hypothesis that fraX mutant mice have an exaggerated stress-induced hyperthermic response, and that this is attenuated by antagonism of group I metabotropic glutamate receptor type 5 (mGluR5) function. The proposed research will build upon initial findings in the adult male Fmr1-KO to test the general hypothesis that in fraX there is a dysregulated HPA axis that leads to a heightened stress response, and that antagonism of the group I mGluR5 will reduce stress-related anxiety seen in this syndrome. Given that stress results in cognitive impairment and has been reported by some to increase dendritic spine densities, two attributes of fraX, studies on stress and the HPA axis in fraX may give valuable insight into the cause of mental retardation in this syndrome.

描述（由申请人提供）：脆性 X 综合征（fraX）是由脆性 X 智力低下蛋白（FMRP）丢失引起的，是遗传性智力低下的最常见原因。 除了认知障碍之外，fraX 的特点是异常的“压力相关”行为，与未受影响的兄弟姐妹相比，患有 fraX 的儿童的基础和压力诱导的肾上腺激素皮质醇唾液水平更高。 这些数据表明 fraX 中下丘脑-垂体-肾上腺 (HPA) 轴功能发生了改变。 已经开发出 fraX 小鼠模型，该模型表现出该综合征的几个特征，并有望识别 Fmr1 缺失的细胞和行为后果。 研究人员的工作表明，脆性 X 智力低下 1 基因敲除 (Fmr1-K0) 小鼠对压力的反应也比野生型小鼠更强，包括基因表达和糖皮质激素水平升高。 这些数据表明 Fmr1-KO 表现出超应激反应，类似于人类 fraX 的表型，但需要更多信息来了解 HPA 轴改变的程度、这种功能障碍的细胞基础以及潜在的治疗靶点。 拟议研究的目标是获得此类信息，并为理解 fraX 中夸大的压力反应对认知障碍的影响奠定基础。 提出了三个目标。 具体目标 1 将检验以下假设：脆弱 X 突变体中 HPA 张力普遍增加（目标 1A 和 1B），并且慢性应激会加剧基因型之间的差异（目标 1A）。 在目标 1A 中，将在处理（无应激）和应激 Fmr1-KO 中分析三个年龄（3 个月、12 个月、24 个月）的促肾上腺皮质激素 (ACTH) 释放和促肾上腺皮质激素释放因子受体 1 (CRH-R1) mRNA 水平和WT小鼠。 目标 1B 将检查 Fmr1-KO 和 WT 中的基础、每日皮质酮波动，以确定水平是否像 fraX 人类中那样发生变化。 具体目标 2 将检验以下假设：与 WT 小鼠 (Aim 2A) 相比，在光学显微镜水平上，固定应激将改变 fraX 突变体中糖皮质激素受体的亚细胞区室化，特别是，在 fraX 突变体中糖皮质激素受体的水平更高。使用蛋白质印迹分析，在基础条件下和应激后 (2B) 下，与 WT 相比，Fmr1-KO 的皮质细胞的核部分。 具体目标 3 将检验以下假设：fraX 突变小鼠具有过度的应激诱导的高温反应，并且这种反应会因 I 组代谢型谷氨酸受体 5 型 (mGluR5) 功能的拮抗作用而减弱。 拟议的研究将建立在成年男性 Fmr1-KO 的初步发现的基础上，以测试一般假设，即 fraX 中存在失调的 HPA 轴，导致应激反应加剧，并且 I 组 mGluR5 的拮抗作用将减少与应激相关的应激反应。焦虑症见于该综合征。 鉴于压力会导致认知障碍，并且据报道会增加树突棘密度（fraX 的两个属性），因此对压力和 fraX 中的 HPA 轴的研究可能会为该综合征中精神发育迟滞的原因提供有价值的见解。