Molecular analysis of the SMN and NAIP genes in Iranian spinal muscular atrophy patients

Background:  Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by degeneration of spinal cord anterior horn cells, leading to muscular atrophy. SMA is clinically classified into three subgroups based on the age of onset and severity. The majority of patients with SMA have homozygous deletions of exons 7 and 8 of the survival motor neuron ( SMN ) gene. The purpose of the present study was to determine the frequency of SMN and neuronal apoptosis inhibitory protein ( NAIP ) gene deletions in Iranian SMA patients. Experience in prenatal diagnosis of SMA in this population is also reported.
Methods:  To study the frequency of deletions of SMN and NAIP genes in an Iranian sample group, 75 unrelated SMA patients (54 type I, eight type II and 13 type III) were analyzed according to the methods described by van der Steege et al and Roy et al .
Results:  Homozygous deletion of SMN1 exons 7 and/or 8 were identified in 68 out of 75 patients (90%). Deletion of exon 5 of the NAIP gene was found in 40/54 of type I, 2/8 of type II and 1/13 of type III patients.
Conclusions:  Deletion of the SMN1 gene is a major cause of SMA in Iran, and NAIP gene deletions were common in the present patients with type I SMA. Also, the incidence of NAIP deletion is higher in more severe SMA.     

Deletion analyses of SMN1 and NAIP genes in Malaysian spinal muscular atrophy patients

BACKGROUND: The survival motor neuron 1 (SMN1) gene has been recognized to be responsible for spinal muscular atrophy (SMA) because it is homozygously deleted in more than 90% of SMA patients, irrespective of their clinical severity, whereas the neuronal apoptosis inhibitory protein (NAIP) gene is now considered to be a modifying factor of the severity of SMA. In Malaysia, it remains to be elucidated whether deletion of the SMN1 gene is also a main cause of SMA or whether deletion of the NAIP gene is found in the SMA patients. METHODS: To clarify the pathogenesis of SMA in Malaysia, a deletion analysis of the SMN1 and NAIP genes was performed in 24 Malaysian SMA patients. Deletion analysis of exons 7 and 8 of the SMN1 gene was performed according to the method described by van der Steege et al., while deletion analysis of exon 5 of the NAIP gene was performed according to a method described by Roy et al. RESULTS: Homozygous deletion of SMN1 exon 7 and exon 8 were identified in 19 out of 24 patients (79%). As to the NAIP gene, deletion of exon 5 was detected in six out of 24 patients (25%). NAIP gene deletion was correlated with severity of the disease. CONCLUSIONS: Deletion of the SMN1 exon 7 is a major cause of SMA in Malaysia, and NAIP gene deletions are not rare in type I SMA in Malaysia. The lower percentage of the SMN1 gene deletion may be due to the possibility that the present study included some patients without SMN1 gene abnormality and/or some patients with non-deletion type mutations in the SMN1 gene.     

Correlation between deletion patterns of SMN and NAIP genes and the clinical features of spinal muscular atrophy in Japanese patients

We conducted molecular analysis of two candidate genes for spinal muscular atrophy (SMA), the survival motor neuron gene (SMN) and the neuronal apoptosis inhibitory protein gene (NAIP), in 16 Japanese patients with SMA and compared the phenotypic features of SMA in these patients with the corresponding genotypes. Exons 7 and/or 8 of SMN were homozygously deleted in 11 SMA type I (Werdnig-Hoffmann disease) patients, two SMA type II patients and one SMA type III patient. Exons 5 and 6 of NAIP were homozygously deleted in six SMA type I patients. No patient had a deletion in NAIP without a deletion in SMN. Mechanical ventilation was required during the first 7 months of life in the SMA type I patients who had a deletion in both SMN and NAIP. Ventilatory support was initiated within 2 years after birth in patients who had a deletion in SMN but not in NAIP. We detected homozygous deletion of exon 5 of NAIP in the unaffected mothers of two SMA type I patients. In these families, the patients exhibited a deletion in both SMN and NAIP. The parents and unaffected siblings of these patients did not have a deletion in SMN. The present findings support the hypothesis that SMN deletion plays an important role in the development of SMA and suggest that combined deletion of both SMN and NAIP may be relevant for determining the disease severity.     

脊髓性肌萎缩症SMN1和SMN2基因拷贝数变异分析

目的:探讨运动神经元存活（SMN）1和SMN2基因拷贝数变异与脊髓性肌萎缩症（SMA）患儿临床表型的关系。方法:以2011年10月至2012年12月在复旦大学附属儿科医院临床诊断SMA患儿为研究对象,采用基因组DNA多重连接探针扩增（MLPA）技术进行SMN1基因缺失和SMN2基因拷贝数变异检测,探讨拷贝数变异与SMA临床分型的关系。结果:41例临床诊断SMA患儿行基因检测,其中SMN1基因第7和（或）8外显子缺失37例（90.2％）进入分析,男女之比为1∶0.8,发病年龄为（7.5±7.0）个月。Ⅰ型20例（54.1％）,Ⅱ型15例（40.5％）,Ⅲ型2例（5.4％）,发病年龄分别为（2.9±1.8）、（10.7±1.9）和（30.0±8.5)个月。37例SMN1基因第7和（或）8外显子缺失患儿中,18例SMN2基因第7和8外显子拷贝数为2个,其中13例（72.2％）为Ⅰ型,5例（27.8％）为Ⅱ型;19例SMN2基因第7和8外显子拷贝数增加（拷贝数3或4）,其中7例（36.8％）为Ⅰ型,10例（52.6％）为Ⅱ型,2例（10.5％）为Ⅲ型,两组差异有统计学意义。5例患儿父母行SMN1基因检测,共检出杂合缺失9例,其中4例患儿父母均为SMN1基因第7和8外显子杂合缺失,1例患儿父亲为SMN1基因第7和8外显子杂合缺失,母亲未检测到纯合或杂合缺失。结论:SMN1基因第7和（或）8外显子纯合缺失是SMA致病主要原因,SMN2基因拷贝数增加与SMA表型严重程度呈负相关。     

脊髓性肌萎缩症患儿SMN1和SMN2基因拷贝数与临床表型的相关性分析

目的 对脊髓性肌萎缩症（SMA）患儿的运动神经元存活基因1（SMN1）和SMN2拷贝数与临床表型之间的关系进行分析,提高对SMA患儿的早期诊断和临床干预水平。方法 选取45例SMA患儿,应用多重连接依赖性探针扩增技术对SMN1和SMN2基因拷贝数进行检测,分析SMN基因拷贝数同临床表型之间的关系。结果 45例SMA患儿中,SMN1第7和8外显子纯合缺失者为42例,占93%（42/45）;仅有第7外显子缺失者为3例,占7%（3/45）。SMA不同临床分型和SMN1基因第7、8外显子缺失类型间无相关性（P > 0.05）;SMA患儿和健康儿童的SMN2基因拷贝数分布差异有统计学意义（P < 0.05）,前者以2和3拷贝者居多,后者以1和2拷贝者居多;不同SMA临床分型间SMN2拷贝数分布差异有统计学意义（P < 0.05）,SMN2基因为2拷贝者发病年龄明显小于3和4拷贝者。Ⅰ型SMA患儿中SMN2拷贝数以2或3拷贝者居多,Ⅱ型以3拷贝者居多,Ⅲ型以3或4拷贝者居多。随着SMN2拷贝数增加,患儿发病年龄越大,保有的运动功能和临床结局越好,SMN2基因拷贝数同临床结局间的关系存在显著性差异（P < 0.05）。结论 SMN2基因通过剂量补偿效应减轻SMA疾病严重程度,SMN2拷贝数同SMA临床表型具有相关性,可将其作为预测疾病严重程度的依据之一。     

Correlation of SMN2, NAIP,p44, H4F5 and Occludin genes copy number with spinal muscular atrophy phenotype in Tunisian patients

ObjectivesSpinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder which is characterized by a high clinical variability with severe, intermediate, mild and adult forms. These forms are caused, in 95% of cases, by a homozygous deletion of exon 7 of SMN1 gene. Our purpose was the determination of a possible genotype–phenotype correlation between the copy number of SMN2, NAIP, p44, H4F5 and occludin genes localized in the same SMN1 region (5q13) and the severity of the disease in SMA Tunisian patients.Patients and methodsTwenty six patients affected by SMA were enrolled in our study. MLPA and QMPSF were used to measure copy numbers of these genes.ResultsWe found that 31.3% of type I patients carried one copy of SMN2, while all patients of other forms had at least 2 copies. NAIP was absent in 87.5% of type I patients. Furthermore, all SMA type I patients had one copy of H4F5. No correlation was found for p44 and occludin genes.ConclusionThere is a close relationship between SMN2, NAIP and H4F5 gene copy number and SMA disease severity, which is compatible with the previous reports.     

SMN1基因实时荧光定量分析在脊髓性肌萎缩携带者检测中的应用

目的：脊髓性肌萎缩（spinal muscular atrophy, SMA）是以脊髓前角运动神经元退化变性为特征的一种常见的常染色体隐性遗传病。SMA的发病率为1/10 000,携带者频率为1/50,因此,对于运动神经元存活基因（survival motor neuron,SMN1）缺失携带者的检测在遗传咨询中尤为重要。然而SMA位点的重复使得携带者的检测比较困难。该研究的目的是探讨SMN1基因定量分析在SMA携带者检测中的作用。方法：应用TaqMan技术的实时荧光定量PCR方法对109例不同临床表型的SMA患者父母和40例正常对照者的SMN1基因拷贝数进行检测。结果：①SMA肯定携带者的SMN1基因的平均拷贝数为0.777±0.035,变异系数（CV）值4.5%;正常人（1例,用于验证检测方法的重复性）SMN1基因的平均拷贝数为2.064±0.120,CV值5.8%;②SMA患者父母SMN1基因平均拷贝数为0.798±0.108,CV值13.5%;正常人（38/40,为人群SMN1拷贝数）SMN1基因平均拷贝数为2.106±0.18,CV值8.5%。结论：SMA患者父母和正常对照者的SMN1拷贝数的分布不同,前者为1个拷贝的SMN1基因;后者以2个拷贝的SMN1基因为主。因此,SMN1基因定量检测可用于区分大部分正常人和SMA携带者。 ［中国当代儿科杂志,2007,9（5）：457-460］     

Molecular diagnosis of spinal muscular atrophy

The frequency of deletions within the survival motor neurone (SMN) and neuronal apoptosis inhibitory protein (NAIP) genes in patients with spinal muscular atrophy (SMA), and the impact of this on the diagnosis and prenatal diagnosis of SMA, were investigated by molecular analysis of stored DNA and retrospective review of case notes. In type I SMA, 16 of 17 cases were homozygously deleted for exons 7 and 8 of SMN, 14 of 17 were homozygously deleted for exon 5 of NAIP, and 13 of 17 were deleted for both. In types II and III SMA, seven of nine cases were deleted for exons 7 and 8 of SMN. Deletions of SMN and NAIP occurred in four of nine cases. With one exception, the deletion genotypes of probands, affected siblings, and terminated fetuses were identical. Molecular studies are replacing conventional investigations for SMA and have a high uptake prenatally.

     

儿童脊髓性肌萎缩症的基因学研究

目的：研究我国儿童型脊髓性肌萎缩症(SMA)患者的运动神经元生存 (SMN)基因及神经细胞凋亡抑制蛋白 (NAIP)基因外显子的缺失情况,以探讨此二种基因与SMA表型之间的关系。方法：应用PCR和PCR -酶切法检测15例Ⅰ～Ⅲ型SMA患者(Ⅰ型4例,Ⅱ型3例,Ⅲ型8例)、20例表型正常的SMA直系亲属及30例正常对照的SMN基因的第7,8号外显子和NAIP基因的第5 ,6号外显子缺失情况。结果：7例Ⅰ型和Ⅱ型SMA患者中6例纯合缺失SMN基因外显子7和8,1例纯合缺失外显子7而保留外显子8;8例Ⅲ型SMA患者仅1例有外显子7和8的缺失,余7例均无SMN基因的缺失;15例Ⅰ～Ⅲ型SMA患者均未检测到NAIP基因外显子5和 /或 6的缺失。结论：Ⅰ型、Ⅱ型SMA可通过SMN基因第7,8号外显子的检测进行确诊,方法简便可靠,Ⅲ型SMA患者SMN基因缺失率低,故通过检测SMN基因 7,8外显子进行基因诊断尚需谨慎,NAIP基因在SMA发病中的作用尚不清楚,有待进一步研究。     

疑似脊髓性肌萎缩症患儿338例的运动神经元存活基因分析

目的 研究儿童脊髓性肌萎缩症(SMA)运动神经元存活基因SMN1缺失和诊断的意义.方法 根据国际诊断标准、病例随访和基因分析结果对338例疑似SMA的患儿进行诊断和分型.应用PCR-酶切方法分析患儿SMN1基因外显子7和外显子8的纯合缺失.应用等位基因特异PCR结合变性高效液相色谱分析(DHPLC)方法分析患儿的SMN1基因拷贝数,确定杂合缺失.结果 (1)确诊SMA 267例,其中Ⅰ型143例,Ⅱ型82例,Ⅲ型42例,分别占53.6%、30.7%和15.7%.(2)267例SMA患儿的SMN1基因缺失分析显示:SMN1基因外显子7和8均纯合缺失为183例,占68.5%(183/267),仅外显子7纯合缺失,外显子8不缺失为34例,占12.7%(34/267),外显子7杂合缺失为33例,占12.4%(33/267),非缺失为17例,占6.4%(17/267),未见SMN1基因外显子8的单独缺失.(3)Ⅰ型和Ⅱ型SMN1基因缺失率相近.Ⅲ型SMN1基因纯合缺失率较低于Ⅰ型和Ⅱ型,杂合缺失率较高于Ⅰ型和Ⅱ型.结论 (1)我国儿童SMA的SMN1基因纯合缺失和杂合缺失频率提示,SMN1基因突变存在种族异质性,SMN1基因内微小突变需要研究.(2)SMN1基因诊断具有特异性和无创性,80%SMA患儿通过SMN1基因纯合缺失分析得到诊断.(3)Ⅲ型SMA的临床诊断和基因分析需要进一步研究.     

85例脊肌萎缩症疑诊患儿的基因诊断和临床再评估

目的 确定运动神经元存活基因1(survival motor neuron gene 1,SMN1)纯合缺失在中国脊肌萎缩症(spinal muscular atrophy,SMA)患儿中的发生频率,判断SMN1基因纯合缺失检测在中国SMA患儿诊断中的临床价值,探讨基因检测后的临床回访在SMA疑诊患儿临床诊疗中的作用.方法 使用多聚酶链反应和限制性片段长度多态性的方法 (polymerase chain reaction and restriction fragment length polymorphism,PCR-RFLP)对85例临床疑诊SMA的患儿样本进行SMN1基因7号外显子纯合缺失检测.由小儿神经专科医师对SMA患儿进行分型,并对基因检测阴性的患儿依照SMA的诊断标准,必要时结合组织学病理检查进行临床再评估.结果 在85例中,57例(67%)检出SMN1纯合缺失.在19例随访的基因检测阴性患儿中,15例不符合SMA的诊断,4例可维持SMA的诊断.在确诊的SMA患儿中,SMN1纯合缺失率为95%.Ⅰ、Ⅱ、Ⅲ型SMA患儿的SMN1纯合缺失检出率分别为96%、93%和100%,SMA临床分型与SMN1纯合缺失率无显著相关性.结论 中国SMA患儿中SMN1基因纯合缺失约为95%,与高加索人群数据相似.SMN1纯合缺失检测应成为中国SMA疑诊患儿的首选诊断和排除诊断方法 .SMN1纯合缺失检测后患儿的临床回访对SMA疑诊患儿的临床诊疗具有重要意义.     

儿童型脊肌萎缩症SMN基因缺失与微突变检测

目的：研究儿童型脊肌萎缩症(SMA)患者中运动神经元生存基因缺失与微突变情况。方法：收集经临床和肌肉活检确诊的SMA I~III型25例,其中I型5例,II型3例,III 17例及直系亲属24例。采用PCR-RFLP检测SMNt缺失情况,对无SMNt缺失的患者及SMA直系亲属,应用PCR-SSCP结合DNA序列分析的方法,进行SMN基因微突变分析。结果：5例I型和3例II型SMA患者均见SMNt缺失,缺失率100%,6例III型见缺失,缺失率35%(6/17)。11例无缺失的SMA III型患者的gDNA编码区域未发现微突变;24例SMA的直系亲属中未发现SMN基因缺失及突变。结论：①检测到SMNt外显子7缺失可作为SMA的确诊手段,有望替代肌电图和肌活检等有创检查;②对无SMNt外显子7缺失的III型SMA患者,要结合临床进行诊断;③该组无SMNt缺失的III型患者未发现微突变,提示存在遗传异质性。[中国当代儿科杂志,2005,7(6):489-492]     

中国脊髓性肌萎缩症患儿的SMN基因学研究

目的：明确中国人各型脊髓性肌萎缩症(SMA)患儿SMN1基因外显子7和8缺失,SMN基因转变及微小突变情况。方法：对106例患者,采用PCR-RFLP检测基因缺失,RFLP筛查基因转变,并对PCR产物进行测序分析。基因转变率比较采用Fisher精确检验法进行统计学分析。结果：SMA患儿纯合SMN1外显子7和/或8缺失比率为91.5%,发现1例SMA中存在SMN1外显子7保留,而SMN1非编码外显子8缺失。在SMN1外显子7缺失而无外显子8缺失的患者中,各型间基因转变率差别无统计学意义,在SMN1外显子7缺失的SMA中,其基因转变率为8.3%。SMN第7外显子附近未发现基因微小突变。结论：SMN1基因外显子7和/或8缺失为中国SMA患儿的主要病因。SMA中存在SMN基因转变现象。SMN1基因外显子8的单独缺失可能致病。SMN1基因外显子7附近可能不是此病微小突变的热点区域。［中国当代儿科杂志,2010,12（7）：539-543］     

等位基因特异性扩增法检测脊髓性肌萎缩运动神经元生存基因缺失

目的：用单链构象多态性(SSCP)、限制性片段长度多态(RFLP)的方法诊断脊髓性肌萎缩(SMA)较普遍,但方法复杂。该文采用等位基因特异性扩增法进行SMA基因诊断,以探讨该方法的实用性和特异性。方法：应用等位基因特异性扩增法对40名SMA患者(Ⅰ型15例,Ⅱ型17例,Ⅲ型8例)和40名正常对照进行运动神经元生存基因(SMN)基因外显子7的基因缺失研究。所有SMA患者均经RFLP方法证实缺失SMN1基因外显子7。结果：等位基因特异性扩增法检测所有SMA患者均存在SMN1基因外显子7缺失,与RFLP的结果一致(诊断符合率为100%)。结论：等位基因特异性扩增是既简便又实用的SMA基因诊断方法。     

小儿进行性脊髓性肌萎缩83例临床分析

目的总结小儿进行性脊髓性肌萎缩(SMA)各类型的临床表现、神经电生理及肌肉病理特点,提高对本病的认识水平并探讨基因诊断及产前诊断的临床意义。方法83例各型SMA患儿,男55例,女28例,年龄1d∽14岁,平均23．7个月,对本组病例进行临床特点、神经电生理、肌肉病理及基因分析。结果83例SMA临床分为3型,其中SMA-1型60例,SMA-2型19例,SMA-3型4例,3型SMA各有特点,但临床均表现为近端肌肉无力,肌张力低下。本病为单纯运动神经元受累,故患儿电生理表现均为神经源性损害而无感觉神经受累及明显的运动神经传导速度减慢;2例行肌活检显示大组萎缩肌纤维;13例行运动神经元生存基因(SMN)检测,11例外显子7和8联合缺失,1例仅第7外显子缺失,1例仅第8外显子缺失。结论根据临床特点,电生理,肌肉病理及基因诊断可与其他松软婴综合征鉴别,而能确诊SMA。基因诊断可为产前诊断提供依据,达到预防本病发生的目的。     

A population-based study of genotypic and phenotypic variability in children with spinal muscular atrophy

Aims: To describe the occurrence of spinal muscular atrophy (SMA) in childhood; to evaluate if any of the genes in the SMA region on chromosome 5q13 correlates with disease severity; to make genotype–phenotype correlations; to evaluate the variability of different disease alleles in carriers and the sensitivity of multiplex ligation-dependent probe amplification (MLPA) for detecting carriers.
Methods: In a population-based study from Western Sweden MLPA was used to determine the copy-numbers of several genes in the SMA region (SMN1, SMN2, BIRC1, GTF2H2 and SERF1A) in SMA-patients and their parents.
Results: We estimated the incidence of SMN1-related SMA in childhood at 1 in 11 800 live births and confirmed the relationship between the number of SMN2 copies and the severity of disease. No other direct relationships were found. All but one of the analysed parents were confirmed as carriers by MLPA analysis. A total of at least 30 different disease alleles were identified and no specific disease allele represented more than 15% of the total.
Conclusion: The childhood incidence of SMA in the Swedish population is around 1 in 12 000 live births and it is unlikely that there is any founder effect involved in SMA in western Sweden.     

117例儿童脊髓性肌萎缩症自然病史分析

目的 对重庆及周边地区脊髓性肌萎缩症（spinal muscular atrophy,SMA）的自然病史进行分析,为开展SMA的综合管理、基因修饰治疗提供临床依据。 方法 回顾性分析117例SMA患儿的临床资料及生存现状。 结果 117例患儿中,1型SMA 62例（53.0%）、2型45例（38.5%）、3型10例（8.5%）,中位起病年龄分别为2、10、15月龄。1型SMA起病、就诊、确诊时间均早于2、3型SMA（P<0.05）,1型SMA就诊时间窗（起病年龄至就诊年龄）短于2、3型SMA（P<0.05）。肺炎为首发症状、抬头无力、哭声无力、进食费力多见于1型SMA（P<0.05）,2型SMA脊柱侧弯和下肢关节挛缩发生率高于1型（P<0.05）。117例（100%）SMA患儿均为SMN1基因纯合缺失,其中以7号外显子纯合缺失最常见（68.4%,80/117）。1型SMA的6年生存率仅为10%±5%,低于2、3型SMA（P<0.05）。起病年龄≤3月龄、肺炎为首发症状、抬头无力为1型SMA死亡的危险因素（P<0.05）。2型SMA运动能力可呈非线性倒退。 结论 各型SMA患儿临床表现、生存率均存在异质性,1型SMA生存率低,2型SMA运动能力可呈非线性倒退,临床上应早期识别及管理SMA。     

Étude de la corrélation génotype–phénotype dans l’amyotrophie spinale infantile (ASI) dans une famille marocaine

Spinal muscular atrophy (SMA) is an autosomal recessive disorder with a highly variable clinical course and prognosis. We report on the cases of three siblings with SMA. The weakness muscular observes at three siblings but more earlier and severe to the index case with a fast evolution towards respiratory distress syndrome resulting in its death at 5 years. The homozygous deletions of exons 7 and 8 of the telomeric SMN gene were found in all three siblings. No child showed deletion of NAIP gene. Muscular weakness and respiratory distress severity however were different among the siblings. The index patient died at the age of 5 because of respiratory insufficiency. Several molecular mechanisms may be involved in such phenotypic variability. The PCR-RFLP method allows to confirm clinical diagnosis of SMA in children, while avoiding more invasive methods such as EMG and muscular biopsy. However, this diagnostic tool does not allow yet the distinction between different clinical forms of SMA.