Chromatin remodeling in transgenic mouse models of HD

亨廷顿病是一种常染色体显性遗传的神经退行性疾病，目前尚无有效的治疗方法。虽然已经提出了一些致病机制，转录失调已成为一个潜在的关键方面。在HD的转基因小鼠模型中，已经描述了mRNA稳态水平的许多改变。然而，mRNA扰动的机制尚不清楚。阐明这些机制将有重大意义的理解和发展的未来治疗HD。 在真核生物中，基因表达通过染色质的修饰和与特定转录因子的结合来调节。虽然转基因HD小鼠（R6/2）脑中稳态mRNA水平的改变是转录失调的事实证据，但尚不清楚染色质结构是否存在特异性改变。在这个项目中，我们将探讨染色质重塑转基因HD小鼠模型。首先，我们将确定光神霉素--一种与DNA富含GC的区域结合的金黄色抗生素，已被证明能延长R6/2小鼠的寿命--是否能纠正mRNA表达异常 我们之前在这些小鼠中描述过。我们将使用受体结合放射自显影和原位杂交来进行这些分析。接下来，我们将试图确定转录因子家族的作用，Sp家族，一组基因的表达已知在R6/2小鼠中被改变。我们将探讨Sp和相关的锌指转录因子的相互作用，通过使用染色质免疫沉淀（CHIP）分析与实时PCR检测。最后，我们将探讨光辉霉素逆转R6/2小鼠染色质异常的能力。 总之，这些实验将阐明亨廷顿病模型中转录失调的分子机制。这种阐明的一个中央致病机制将打开通往合理的，机制靶向治疗这一毁灭性疾病的道路。

Huntington's disease is an autosomal dominant neurodegenerative disease for which there is currently no effective treatment. Although a number of pathogenic mechanisms have been proposed, transcriptional dysregulation has emerged as a potential critical aspect. In transgenic mouse models of HD, numerous alterations in the steady state levels of mRNA have been described. However, the mechanisms underlying mRNA perturbation are undefined. Elucidation of such mechanisms will have significant relevance to the understanding and development of future treatment of HD. In eukaryotes, gene expression is regulated through modification of chromatin and association with specific transcription factors. While alteration of steady state mRNA levels in transgenic HD mouse (R6/2) brain is de facto evidence of transcriptional dysregulation, it is yet unknown whether there are specific alterations in chromatin structure. In this project, we will explore chromatin remodeling in a transgenic HD mouse model. First, we will determine if mithramycin--an aureolic antibiotic that binds to GC-rich regions of DNA and which has been shown to extend lifespan in R6/2 mice--corrects mRNA expression abnormalities that we have previously described in these mice. We will use receptor binding autoradiography and in situ hybridization to perform these analyses. Next, we will seek to determine the role of a fatnily of transcription factors, the Sp family, with a set of genes whose expression is known to be altered in R6/2 mice. We will explore the interactions of Sp and related zinc finger transcription factors by using Chromatin ImmunoPrecipitation (CHIP) assays with real-time PCR detection. Finally, we will explore the ability of mithramycin to reverse chromatin abnormalities in the R6/2 mice. Taken together, these experiments will elucidate the molecular mechanisms underlying transcriptional dysregulation in a model of Huntington's disease. Such elucidation of a central pathogenic mechanism will open the way towards rational, mechanism-targeted therapy for this devastating disease.