Chromatin remodeling in transgenic mouse models of HD

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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.