Functional Role of Micro RNAs in Huntington's Disease Pathogenesis

描述(申请人提供)：亨廷顿病(HD)是一种毁灭性的慢性神经退行性疾病。目前还没有有效的治疗方法，这种疾病普遍是致命的。HD是由HD基因的一种高渗透性常染色体显性突变引起的。为了更好地了解hTT基因突变表达的生物学效应和纹状体早期受累的情况，我们利用miR表达芯片检测了正常人类背侧纹状体和正常腹侧纹状体中miR表达的变化。同样，我们比较了HD患者和对照组背侧纹状体组织中miR的表达水平。我们已经识别出区分正常背侧和正常腹侧纹状体的miR信号，以及区分正常和HD背侧纹状体的miR信号。我们的假设是，miR在正常组织中的差异表达可能为 导致MSN对突变的HTT表达的易感性增加。我们通过用miR文库导入表达突变HTT的神经元细胞系来扩展这些初步研究。我们已经确定，在突变的HTT表达的神经元中，三个特定的miRs的过度表达是保护的，而另外一个miRs的过度表达是有毒的。这些数据导致了这个项目的总体假设：miRs的差异表达可能使背侧纹状体对早期神经元死亡敏感，突变的htt表达可能导致miR表达的额外失调，并加剧HD细胞的死亡表型。此外，我们假设这些MIR及其靶基因是HD潜在的新治疗靶点。这将通过三个具体目标进行研究：1)确定操纵HD小鼠模型大脑中的miR水平是否可以改变疾病的发病和/或进展。2)确定miR-155基因敲除在背侧纹状体较腹侧纹状体增加，是否会改变HD小鼠模型的发病和进展。3)确定差异表达miRs的下游靶点，寻找HD新的潜在治疗靶点。因此，本申请中描述的工作的关键意义是确定新的关键调控途径(即miR)如何使背侧纹状体神经元对细胞死亡敏感，如 以及突变型HTT如何主动改变miR的表达，导致细胞死亡途径的公开激活。我们的希望是，通过了解背侧纹状体的不同之处(即更脆弱)，以及突变的HTT如何改变miR稳态，我们应该能够更好地了解HD的生物学，并开发新的治疗方法来治疗这种毁灭性的疾病。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a devastating chronic neurodegenerative disorder. No effective treatment is available and the disease is universally fatal. HD is caused by a highly penetrant, autosomal dominant mutation in the HD gene. To better understand the biologic affects of mutant htt expression and the early involvement of the dorsal striatum, we determined the changes in microRNA (miR) expression in normal human dorsal striatum versus normal ventral striatum using a miR expression array. Similarly, we compared the miR expression levels in dorsal striatal tissues of HD patients compared to controls. We have identified a miR signature that distinguishes normal dorsal versus normal ventral striatum, and a miR signature that distinguishes between normal and HD dorsal striatum. It is our hypothesis that the differential miR expression in normal tissue may provide clues to the cause of the increased vulnerability of MSN to mutant htt expression. We have expanded these preliminary studies by transfecting mutant htt expressing neuronal cell lines with a miR library. We have determined that over-expression of three specific miRs is protective in mutant htt expressing neurons while overexpression of one additional miRs is toxic. These data lead to the overall hypothesis of this project: Differential expression of miRs may sensitize dorsal striatum to early neuronal death and that mutant htt expression may lead to additional disregulation of miR expression and exacerbate the HD cell death phenotype. Furthermore, we hypothesize that these miRs and their target genes represent potential novel therapeutic targets for HD. This will be investigated using three specific aims: 1) To determine if manipulation of miR levels in the brain of mouse models of HD can alter disease onset and/or progression. 2) To determine if knockout of miR-155, which is increased in dorsal striatum as compared to ventral striatum, will alter HD onset and progression in a mouse model of HD. 3) To determine the downstream targets of differentially expressed miRs to identify new potential therapeutic targets for HD. Thus, the key significance of the work described in this application is to determine how a new critical regulatory pathway (i.e. miR) may both sensitize dorsal striatal neurons to cell death, as well as how mutant htt may actively alter miR expression resulting in overt activation of cell death pathways. Our hope is that by understanding what makes the dorsal striatum different (i.e. more vulnerable), as well as how mutant htt alters miR homeostasis, we should be able to both better understand the biology of HD as well as develop novel therapeutic approaches for the treatment of this devastating disease.