Functional Role of Micro RNAs in Huntington's Disease Pathogenesis

描述（由申请人提供）：亨廷顿病（HD）是一种破坏性慢性神经退行性疾病。没有有效的治疗方法，这种疾病普遍是致命的。HD是由HD基因中的高度外显常染色体显性突变引起的。为了更好地了解突变htt表达的生物学效应和背侧纹状体的早期参与，我们使用miR表达阵列确定了正常人背侧纹状体与正常腹侧纹状体中microRNA（miR）表达的变化。同样，我们比较了HD患者与对照组背侧纹状体组织中的miR表达水平。我们已经鉴定了区分正常背侧纹状体与正常腹侧纹状体的miR签名，以及区分正常和HD背侧纹状体的miR签名。我们的假设是，正常组织中miR的差异表达可能为研究miR-1的表达提供线索。 MSN对突变htt表达的脆弱性增加的原因。我们已经扩大了这些初步的研究，通过用miR文库筛选表达突变htt的神经元细胞系。我们已经确定，三种特异性miR的过表达在突变体htt表达神经元中是保护性的，而另外一种miR的过表达是毒性的。这些数据导致本项目的总体假设：miR的差异表达可能使背侧纹状体对早期神经元死亡敏感，并且突变htt表达可能导致miR表达的额外失调并加剧HD细胞死亡表型。此外，我们假设这些miR及其靶基因代表了HD的潜在新治疗靶点。这将使用三个具体目的进行研究：1）确定HD小鼠模型脑中miR水平的操纵是否可以改变疾病发作和/或进展。2)确定miR-155敲除（与腹侧纹状体相比，背侧纹状体中的miR-155增加）是否会改变HD小鼠模型中的HD发作和进展。3)确定差异表达miR的下游靶点，以确定HD的新的潜在治疗靶点。因此，本申请中描述的工作的关键意义是确定新的关键调节途径（即miR）如何既可以使背侧纹状体神经元对细胞死亡敏感， 以及突变体htt如何主动改变miR表达，导致细胞死亡途径的明显激活。我们的希望是，通过了解是什么使背侧纹状体不同（即更脆弱），以及突变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.