Molecular Pathways Regulated By DUX4, an FSHD-Associated Gene

描述（由申请人提供）：面肩肱骨肌营养不良症（FSHD）是一种遗传显性进行性肌肉营养不良症，影响约1/20,000人。虽然该病是由4号染色体上重复序列的缺失引起的，这被认为是不适当地激活了附近的基因，但关键致病基因的身份尚不清楚，该区域基因与肌肉病理的相关机制也尚不清楚。目前对FSHD没有有效的治疗方法。我们在细胞培养系统中筛选了4号染色体FSHD区域的候选基因，并发现了一个对成肌细胞具有极大毒性的基因（双同源结构域转录因子DUX4，它嵌入在4号染色体的D4Z4重复序列中）。通过诱导基因表达系统，我们发现DUX4的表达会导致先前在微阵列和蛋白质组学研究中发现的一组基因的表达发生变化，这些基因在FHSD中被特异性失调，包括应激反应途径的元件和转录因子MyoD。我们进一步表明，这些反应涉及到与Pax7的竞争，Pax7是一种位于肌生成层次顶端的转录因子，具有高度相关的同源结构域。我们建议研究DUX4下游的分子通路，并鉴定与DUX4和Pax7相反调控的肌肉再生相关基因（Aim 1），基于患者来源的D4Z4/DUX4序列的表达，建立新的FSHD细胞和小鼠模型（Aim 2），并验证肌肉的干细胞或祖细胞区室在FSHD中受到DUX4特异性影响的假设（Aim 3）。

DESCRIPTION (provided by applicant): Facioscapulohumeral muscular dystrophy (FSHD) is a genetically dominant progressive muscular dystrophy affecting approximately 1/20,000 individuals. Although the disease is caused by a deletion of repeated sequence on chromosome 4, which is thought to inappropriately activate nearby genes, the identity of the key causative gene is unknown and mechanisms relating genes in the area to muscle pathology are unknown. There is currently no effective treatment for FSHD. We have screened candidate genes from the FSHD region of chromosome 4 in a cell culture system, and identified a gene (the double-homeodomain transcription factor, DUX4, which is embedded within the D4Z4 repeats on chromosome 4) with extreme toxicity to myoblasts. Using an inducible gene expression system, we show that expression of DUX4 causes changes in expression of a set of genes previously identified in microarray and proteomic studies as specifically misregulated in FHSD, including elements of stress response pathways, and the transcription factor MyoD. We further show that these responses involve competition with Pax7, a transcription factor at the apex of the myogenic hierarchy with a highly related homeodomain. We propose to investigate the molecular pathways downstream of DUX4 and identify genes relevant to muscle regeneration that are oppositely regulated by DUX4 and Pax7 (Aim 1), to generate novel cell and mouse models for FSHD based on expression of patient-derived D4Z4/DUX4 sequences (Aim 2), and to test the hypothesis that the stem or progenitor cell compartments of muscle are specifically affected by DUX4 in FSHD (Aim 3). PUBLIC HEALTH RELEVANCE: Facioscapulohumeral muscular dystrophy (FSHD) a genetically dominant progressive muscular dystrophy associated with a deletion of repetitive sequences on chromosome 4. This deletion is thought to deregulate nearby genes and we have shown that one of the genes associated with this deletion, DUX4, causes myoblasts to become sensitive to oxidative stress, and interferes with myogenic pathways by competing with the muscle stem cell master regulator, Pax7. We propose to investigate the molecular pathways downstream of DUX4 and identify genes relevant to muscle regeneration that are oppositely regulated by DUX4 and Pax7 (Aim 1), to generate a mouse model for FSHD based on expression of patient-derived D4Z4/DUX4 sequences (Aim 2), and to test the hypothesis that the stem or progenitor cell compartments of muscle are specifically affected by DUX4 in FSHD (Aim 3).