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）：脆弱的X综合征（FRAX）是由于脆弱的X智力低下蛋白（FMRP）导致的，是遗传性智障的最常见原因。 除了认知障碍外，FRAX的特征是异常的“与压力相关”行为，而FRAX的儿童的基础和应激诱导的肾上腺激素皮质醇水平更高，与未受影响的兄弟姐妹相比。 这些数据表明下丘脑 - 垂体 - 肾上腺（HPA）轴功能在FRAX中发生了改变。 已经开发了一种鼠模型，该模型表现出该综合征的几个特征，并具有识别FMR1缺失的细胞和行为后果的希望。 研究者的工作表明，脆弱的X智力障碍1基因敲除（FMR1-K0）小鼠对胁迫的反应也比野生型小鼠更大，包括基因表达和糖皮质激素水平升高。 这些数据表明，FMR1-KOS表现出一种超压力的反应，类似于人类Frax中的表型，但需要更多的信息就可以改变HPA轴，这种功能障碍的细胞基础和潜在的治疗靶标。 拟议的研究的目的是获取此类信息并为理解夸张的压力反应对FRAX认知障碍的贡献奠定基础。 提出了三个目标。 具体的目标1将检验以下假设：脆弱X突变体中HPA张力的普遍增加（AIMS 1a＆1b），并且基因型之间的差异通过慢性应激增强（AIM 1A）。 在AIM 1A中，将在处理（未加重的fmr1-ko-ko和WT小鼠中分析三个年龄（3 MO，12 MO，24 MO）的肾上腺皮质激素（ACTH）释放和皮质激素释放因子受体1（CRH-R1）mRNA水平。 AIM 1B将检查FMR1-KOS和WTS中的基础昼夜皮质酮波动，以确定是否像Frax人类一样改变了水平。 具体目标2将检验以下假说：与WT小鼠（AIM 2A）相比，在光显微镜水平上，FRAX突变体中糖皮质激素受体的亚细胞隔室化，尤其是使用FMR1-K相比，使用FMR1-K相比，在光中较大的糖层级别的糖层级别的情况下，在光显微镜水平上，尤其是较高的葡萄皮层受体中的糖皮质级别（AIM 2A）。印迹分析。 特定的目标3将检验以下假设：FRAX突变小鼠具有夸张的应激诱导的过度热反应，并且这会因I组A组的拮抗剂5型谷氨酸受体5型（MGLUR5）功能所削弱。 拟议的研究将基于成年男性FMR1-KO的初步发现，以检验一个普遍的假设，即在FRAX中，HPA轴的失调会导致压力增强，并且I组MGLUR5的拮抗作用将减少该综合征中看到的与压力相关的焦虑。 鉴于压力会导致认知障碍，并且有些人据报道增加树突状脊柱密度，两种frax的属性，关于FRAX中的压力和HPA轴的研究可能会给该综合征中的智力迟缓原因提供宝贵的见解。