The Pathogenesis of Facioscapulohumeral Muscular Dystrophy

描述（由申请人提供）：面肩肱骨肌营养不良症（FSHD）是最常见的成人肌肉营养不良症之一。亚端粒大卫星重复序列（D4Z4重复序列）的一个子集的缺失导致大多数FSHD病例，并导致显性遗传性疾病。我们小组最近的研究表明，缺失等位基因上的抑制表观遗传标记减少，调控因子与缺失等位基因的结合增加，D4Z4重复序列产生了一组复杂的编码和非编码rna。这些发现有力地支持了FSHD病理生理学的一个广泛假设：D4Z4重复序列中表观遗传沉默的缺失会通过RNA或蛋白质介导的机制导致导致该疾病的RNA物种的表达增加。我们的研究小组将解决具体和互补的目标，共同验证广泛的假设，并确定FSHD的具体机制，这对未来的治疗发展至关重要。项目1 （van der Maarel博士）的目标是确定4qA161特有的DNA序列和表观遗传变化，这是赋予FSHD病理所必需的。项目2 （Tapscott博士）的目标是确定D4Z4产生的编码和非编码rna是否在FSHD病理中起作用，并确定D4Z4重复区域的转录普遍抑制机制。项目3 （Filippova博士）的目的是确定CTCF与疾病相关等位基因的结合是否调节区域染色质结构、RNA转录或核定位。项目4 （Miller博士）的目标是使用FSHD衍生的IPS细胞来鉴定FSHD的转录和表观遗传决定因素，以及D4Z4区域的调控区域。Tawil博士（核心A）建立了FSHD生物资源核心，从FSHD和对照个体中统一收集和良好表征的生物样本。核心A的目的是从血液样本中收集DNA用于遗传分析，从皮肤和肌肉中收集成纤维细胞和成肌细胞用于生物学研究，以及从肌肉活检中进行组织化学和原位生物学分析。行政核心（核心B）将协调奖助金的行政管理、参与者之间的沟通和报告责任。总之，这些研究结合了遗传、表观遗传、转录和发育方法来定义导致FSHD的分子缺陷，并将为开发治疗方法提供新的基础。

DESCRIPTION (provided by applicant): Facioscapulohumeral muscular dystrophy (FSHD) Is one of the most common adult muscular dystrophies. Deletion of a subset of subtelomeric macrosatellite repeats (D4Z4 repeats) causes most cases of FSHD and results in a dominantly inherited disease. Recent work from our groups have shown a decrease of repressive epigenetic markings on the deleted allele, increased binding of regulatory factors to the deleted allele, and a complex set of coding and non-coding RNAs generated from the D4Z4 repeats. These findings strongly support a broad hypothesis for the pathophysiology of FSHD: loss of epigenetic silencing in the D4Z4 repeat leads to increased expression of an RNA species that causes the disease, either through an RNA or protein mediated mechanism. Our research groups will address specific and complementary aims that together will both test the broad hypothesis and identify the specific mechanism(s) of FSHD, which is critical for future therapy development. The aims of Project 1 (Dr. van der Maarel) will identify the DNA sequences and epigenetic changes specific to 4qA161 that are necessary to confer FSHD pathology. The aims of Project 2 (Dr. Tapscott) will determine whether the D4Z4-generated coding and non-coding RNAs have a role in FSHD pathology and identify mechanisms of generally suppressing transcription from the D4Z4 repeat region. The aims of Project 3 (Dr. Filippova) will be to determine whether CTCF binding on the disease associated allele regulates regional chromatin structure, RNA transcription, or nuclear localization. The aims of Project 4 (Dr. Miller) will be to use FSHD-derived IPS cells to identify the transcriptional an epigenetic determinants of FSHD, and the regulatory regions in the D4Z4 region. Dr. Tawil (Core A) has established an FSHD Bioresources Core with uniformly collected and well-characterized biological samples from FSHD and control individuals. The aims of Core A will be to collect DNA from blood samples for genetic analysis, fibroblast and myoblasts from skin and muscle for biological studies, and muscle biopsies for histochemical and in situ biological analyses. The Administrative Core (Core B) will coordinate the administration of the grant, communications among the participants, and reporting responsibilities. Together, these studies combine genetic, epigenetic, transcriptional and developmental approaches to defining the molecular deficits that cause FSHD and will provide a new basis for developing therapies. PUBLIC HEALTH RELEVANCE: The pathophsiology of FSHD is currently unknown and there are no validated targets or mechanisms that can provide the basis for therapeutic development. The significance of this proposed study is that it will identify and validate specific mechanisms for the pathophysiology of FSHD. The human health relevance of this work is that it will provide a new basis for rational therapeutic development for FSHD. PROJECT 1 Principal Investigator: Silvere van der Maarel, PhD Title: The Genetic and Epigenetic Basis for FSHD Description (provided by applicant): We have demonstrated that FSHD is caused by a contraction-cfepencfenf (FSHD1) or contractionindependent (FSHD2) change in chromatin structure of D4Z4 only when this contraction occurs on a specific genetic background (4qA161). This leads to the hypothesis that a change in D4Z4 chromatin structure on the 4qA161 haplotype is essential for FSHD pathology. Therefore, the long-term goal is to identify the specific DNA sequences and the epigenetic modifications that together confer pathogenicity to 4qA161. Aim 1 will identify and functionally characterize the disease haplotype-specific sequence variants of the distal repeat unit and flanking pLAM sequence. Recent studies identified this part of the FSHD locus as the minimal essential region; Aim 2 will identify and functionally characterize the chromatin structure of this minimal essential region test the hypothesis that the D4Z4 repeats regulate DUX4 expression and have a biological role in early embryonic development; and Aim 3 will determine the genetic and epigenetic characteristics of D4Z4 in human ES cells to establish the developmental role of D4Z4 in relation to the clinical features of FSHD. Public Health Relevance: The significance of these studies is that identifying the genetic and epigenetic conditions required for FSHD will provide fundamental insight into the pathophysiology of FSHD as well as providing new avenues for interventional therapies.