Genetic Analysis of Neurodegeneration

神经退行性疾病的遗传分析

• 批准号: 6703648
• 负责人: SUSAN L ACKERMAN
• 金额: $ 31.62万
• 依托单位: JACKSON LABORATORY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6703648
• 关键词: ataxia; cell cycle; free radical oxygen; gene expression; gene mutation; granule cell; immunocytochemistry; laboratory mouse; mitochondria; mitogens; neural degeneration; neurogenetics; oxidative stress; oxidoreductase

Although neurodegenerative disorders are prevalent in the aging human population, the molecular mechanisms underlying these diseases are not well understood. As in humans, genetic lesions have been associated with neurodegeneration in mice. Several mouse mutations exist that result in the abnormal death of embryonic or early postnatal neurons. In contrast, our studies of mice homozygous for the spontaneous mutation harlequin (Hq) have shown that this mutation causes progressive neuron loss in adult mice. Hq mutant mice are characterized initially by a loss of hair in homozygous females and hemizygous males. These mice develop progressive ataxia concomitant with loss of cerebellar neurons. Cell loss in Hq mutants peaks at 5-7 months and is initially confined to granule cells in the caudal cerebellum. Analysis of cell cycle markers demonstrates that granule cell apoptosis is accompanied by abortive cell cycle re-entry. These abnormally cycling cells express sonic hedgehog, a potent mitogen expressed by granule cell precursors, but down-regulated upon terminal differentiation of these cells. The Hq critical region has been refined to a 0.61 cM region of the X Chromosome, and a genomic contig across this region has been assembled. Genetic analysis of transcripts within the Hq region demonstrated that the gene encoding the apoptosis-inducing factor (Aif ), a mitochondrial oxidoreductase, cosegregates with the Hq gene. Further, Aif transcript levels are greatly reduced in pre-ataxic mutant mice, making Aif a likely candidate for the Hq gene. Immunohistochemistry results demonstrate oxidized DNA is present in mutant but not control granule cells, suggesting down-regulation of Aif results in oxidative stress. Experiments outlined in this grant will identify the molecular lesion in the Aif gene in Hq mutant mice. In addition, the effect of the Hq mutation on mitochondrial function and oxidative stress will be analyzed. Lastly, to test whether the ectopic expression of sonic hedgehog is sufficient to cause cell cycle re-entry and subsequent apoptosis, transgenic mice will be generated that abnormally express this molecule in terminally differentiated granule cells. The results of these experiments will allow validation of Hq mutant mice as a model for elucidation of the molecular interplay between oxidative stress, mitogen activation and cell cycle re-entry, and neuronal death in the adult nervous system.

尽管神经退行性疾病在人群衰老中很普遍，但这些疾病的分子机制尚不清楚。 与人类一样，遗传病变与小鼠的神经退行性有关。存在几种小鼠突变，导致胚胎或早期产后神经元的异常死亡。 相比之下，我们对自发突变广素（HQ）纯合的小鼠的研究表明，这种突变会导致成年小鼠的渐进性神经元丧失。 HQ突变小鼠最初的特征是纯合雌性和半合基因雄性的头发损失。 这些小鼠会发展出伴随的渐进性共济失调，而小脑神经元丧失。总部突变体中的细胞损失在5-7个月时达到峰值，最初仅限于尾小脑中的颗粒细胞。 细胞周期标志物的分析表明，颗粒细胞凋亡伴随着流产的细胞周期再进入。 这些异常的循环细胞表达了声音刺猬，这是一种由颗粒细胞前体表达的有效有丝分裂原，但在这些细胞的末端分化后下调。 HQ临界区域已被完善到X染色体的0.61 cm区域，并且已经组装了该区域的基因组重叠群。 HQ区域内转录本的遗传分析表明，编码凋亡诱导因子（AIF）的基因，线粒体氧化还原酶与HQ基因cosegregege cosegregege。 此外，AIF的转录水平大大降低了，在原质突变小鼠中，AIF可能是HQ基因的候选者。 免疫组织化学的结果表明，突变体中存在氧化DNA，但不能控制颗粒细胞，表明AIF的下调导致氧化应激。该赠款中概述的实验将确定HQ突变小鼠AIF基因中的分子病变。 另外，将分析总部突变对线粒体功能和氧化应激的影响。 最后，为了测试声音刺猬的异位表达是否足以引起细胞周期再入口和随后的凋亡，将产生转基因小鼠，以异常表达该分子在末端分化的颗粒细胞中。 这些实验的结果将允许验证HQ突变小鼠，以阐明成人神经系统中氧化应激，有丝分裂原激活和细胞周期再入口和神经元死亡之间分子相互作用的模型。