Genotype-Phenotype Correlations In Movement and Neuromuscular Disorders

临床神经遗传学研究计划的重点是识别和表征与遗传性运动和神经肌肉疾病有关的基因和遗传机制。 肌原纤维肌病：我们先前已经确定结蛋白基因是引起心脏和骨骼肌病的原因。到目前为止，该基因的42个突变已被证明是致病的。致病潜力与结蛋白突变的类型和位置有关：高度保守的2B螺旋结构域中的结蛋白突变尤其具有破坏性，因为2B控制着α-螺旋的完整性，并负责结蛋白细丝的组装和稳定性。非螺旋羧基末端尾部结构域突变也会导致心脏和骨骼肌病，其致病机制尚不清楚。我们已经鉴定并鉴定了Myotilin和ZASP的突变，这是另外两个引起肌原纤维肌病的基因，在表型上与结缔组织病不同。 DSMA-V/CMT2D型周围神经病GLYCyL-tRNA合成酶(GARS)突变的表型和功能分析：我们先前已经发现一个导致大鱼际和第一背侧骨间肌萎缩的基因，以及以运动性远端神经元病/轴索病为主的临床连续性疾病，伴有轻到中度的感觉受累。对疾病相关GARS突变的功能分析表明，突变的GARS蛋白在神经细胞中错误定位，因此内源性GARS相关颗粒存在于轴突投射中。结果提示，突变型GARS在外周轴突中表达，可能在DSMAV/CMT2D的发病机制中起关键作用。 导致特发性震颤的基因的染色体图谱：我们已经确定，获得知情同意，临床评估并收集了10个具有震颤或震颤/肌张力障碍表型的美国家庭成员的血液样本。在两个家系中建立了与染色体6p23上的一个区域的遗传连锁，其综合非淋巴细胞白血病评分为3.125(P=0.0008)，多点LOD评分为4.248，最大两点LOD评分为2.7。单倍型分析导致鉴定出两个家族共有的一个600kB的区间。对14个基因的编码外显子的突变分析发现了大量的序列变异，其中三个预测了编码氨基酸的变化。试图将这些基因与ET发病机制联系起来的功能研究正在进行中。在另外三个患有ET的美国家庭中，染色体11p15上的一个新的有希望的基因座与震颤有关，目前正在研究中。 用于大基因突变检测分析的高效新技术。与恶性高热相关的RYR1基因分析：我们开发了一种可靠的基因筛查策略，该策略基于对从活检骨骼肌提取的RNA样本进行变性高效液相色谱(DHPLC)分析，然后进行cDNA测序-作为检测和鉴定恶性高热(MH)患者RYR1突变的首选方法。这种方法显著地将突变检测率从25%提高到70%，并允许在北美人群中识别导致恶性高热的9种新的RYR1突变。 UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine激酶(GNE)基因突变导致遗传性包涵体肌病：在高加索人、印度人和希腊人家庭中发现了GNE基因突变，从而扩大了GNE突变相关肌病的种族范围。涉及α-营养不良糖链低糖基化的分子疾病机制正在评估中。

The Clinical Neurogenetics research program is focused on identification and characterization of genes and genetic mechanisms involved in hereditary movement and neuromuscular disorders. MYOFIBRILLAR MYOPATHIES: We have previously identified desmin gene as the cause of cardiac and skeletal myopathies. To-date, 42 mutations in this gene have been proven pathogenic. The pathogenic potentials correlate with the type and location of desmin mutations: those within the highly conserved 2B helical domain are especially damaging since 2B controls the integrity of the alpha-helix and is responsible for desmin filament assembly and stability. Pathogenic mechanisms of mutations in non-helical carboxy-terminal tail domain that also cause cardiac and skeletal myopathy remain unknown. We have identified and characterized mutations in Myotilin and ZASP, two other genes causing myofibrillar myopathy that is phenotypically distinct from desminopathy. PHENOTYPIC AND FUNCTIONAL ANALYSIS OF GLYCYL-tRNA SYNTHETASE (GARS) MUTATIONS IN dSMA-V/CMT2D TYPE OF PERIPHERAL NEUROPATHY: We have previously identified a gene causing atrophy in thenar and first dorsal interosseus muscles and a clinical continuum of predominantly motor distal neuronopathy/axonopathy with mild to moderate sensory involvement. Functional analyses of disease-associated GARS mutations have shown that the mutant GARS protein mislocalizes in neuronal cells so that endogenous GARS-associated granules are present in the neurite projections. The results suggest that mutant GARS is expressed in peripheral axons and may play a key role in dSMA-V/CMT2D pathogenesis. CHROMOSOMAL MAPPING OF GENES CAUSING ESSENTIAL TREMOR: We have identified, obtained informed consent, clinically evaluated and collected blood samples from members of ten American families with a tremor or tremor/dystonia phenotype. Genetic linkage to a region on chromosome 6p23 was established in two families with a combined NPL-all score 3.125 (P=0.0008), multipoint LOD score 4.248, and maximal two-point LOD score 2.70. Haplotype analysis led to the identification of a 600-kB interval shared by both families. Mutation analysis of coding exons in 14 genes discovered numerous sequence variants, three of which predicted a change of the encoded amino acid. Functional studies with attempts to implicate these genes in ET pathogenesis are under way. A new promising locus on chromosome 11p15 linked to tremor in three other American families suffering of ET is under study. NOVEL HIGHLY EFFICIENT TECHNIQUE FOR MUTATION-DETECTION ANALYSIS OF LARGE GENES. ANALYSIS OF THE RYANODINE RECEPTOR TYPE 1 (RYR1) GENE ASSOCIATED WITH MALIGNANT HYPERTHERMIA: We developed a reliable genetic screening strategy based on Denaturing high-performance liquid chromatography (DHPLC) analysis of RNA samples extracted from the biopsied skeletal muscle followed by cDNA sequencing - as a method of choice for RYR1 mutation detection and identification in patients with Malignant hyperthermia (MH). This methodology significantly increased the mutation-detection rate from 25% to 70% and allowed to identify nine novel RYR1 mutations causing malignant hyperthermia in North-American populations. MUTATIONS IN UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE) GENE CAUSING HEREDITARY INCLUSION BODY MYOPATHY: Mutations in the GNE gene were identified in Caucasian, Indian and Greek families thus expanding the ethnic spectrum of the GNE mutation-associated myopathy. Molecular disease mechanisms involving hypoglycosylation of alpha-dystroglycan are under evaluation.