成人起病散发性下运动神经元病基因检测的相关研究

Gene test in sporadic adult onset lower motor neuron disease

目的探讨成人散发起病的下运动神经元病(lower motor neuron disease,LMND)患者铜锌超氧化物歧化酶1(superoxide dismutase 1,SOD1)基因、运动神经元存活基因(survive motor neuron,SMN)及雄激素受体(androgen receptor,AR)基因对明确诊断疾病类型的作用。方法收集43例成人散发起病表现为LMND的患者取外周血提取基因组DNA,分别进行聚合酶链式反应(PCR)扩增SOD1基因外显子1-5,SMN基因外显子7及男性LMND患者AR基因外显子1,对产物进行高分辨熔解曲线分析、变性聚丙烯酰胺凝胶电泳分析及测序。结果在43例成年LMND患者中,未发现SOD1基因突变。2例男性患者有SMN1外显子7的纯合缺失,诊断为Ⅲ、Ⅳ型脊髓性肌萎缩(SMA)。在31例男性患者中发现3例AR基因外显子1的CAG三核苷酸重复序列数分别为49、50、52,可诊断肯尼迪病。结论对LMND患者进行SMN1基因外显子7及AR基因外显子1检测,可使部分散发或无明确家族史的患者明确诊断,并可对病情及预后进行评估。

Objective The clinical presentation of adult onset lower motor neuron disorders is variahle, atypical, may be undistinguished in patients who lack the classic signs of each disease such as spinobulbar muscular atrophy （SBMA; Kennedy disease）, multifocal motor neuropathy and spinal muscular atrophy （SMA）. With the identification of genes associated with motor neuron degeneration over the past years, such as superoxide dismutase 1 （SOD1）, survive motor neuron gene 1 （SMN1） and androgen receptor gene （AR）, an accurate molecular diagnosis can be made in some patients with lower motor neuron diseases （LMND）. Present study is adopted to screen whether any mutations of SOD1 gene, homozygous deletion of SMN gene and an expansion of AR gene exists in adult-onset LMND. Methods The genomic DNA was extracted from the leukocytes of whole blood samples in 43 patients with adult onset LMND, the region encoding the five exons of the SOD1 gene was amplified by a polymerase chain reaction （PCR） using five sets of primers previously described. The reaction products were purified and analyzed with an automated DNA sequencer. Exon 7 of SMN1 gene was amplified by PCR and the PCR product was digested by Dral enzyme. Exon 1 of AR gene was amplified by PCR in 31 male LMND patients. The product of each sample was analyzed by electrophoresis on a denaturing polyacrylamide gel. The samples with abnormality findings were analyzed with an automated DNA sequencer. Results There are no mutation among SOD1 gene in 43 LMND cases, while homozygous deletion of SMN1 exon 7 was identified in two cases who were diagnosed as typeⅢ and type Ⅳ SMA respectively. In 31 male LMND cases, three cases with enlarged （CAG） domains in AR exon 1 were identified. The repeat （CAG） numbers are 49, 50, 52 respectively, which should be diagnosis as SBMA. Conclusions Identification of one of these genetic abnormalities will allow specific diagnosis for patients and it is meaningful on their prognosis and therapy.