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SMN基因缺失多重连接探针扩增法检测和识别脊柱肌肉萎缩症的纯合型或杂合型SMN基因缺失
Objective: Spinal muscular atrophy(SMA), an autosomal recessive neuromuscular degeneration of the anterior horn cells of the spinal cord and brain stem, results in one of the most common diseases with muscle fatigue and atrophy. Most SMA cases including all the types are due to the homozygous deletion of at least exon 7 within the survival motor neuron 1 (SMN-1) gene. Although a "golden standard" assay (PCR with mismatch primer followed by enzyme digestion) is very reliable for the identification of homozygous SMN-1 deletion, the carrier detection of heterozygous SMN-1 deletion remains a challenge. Methods: Some PCR-based gene dosage assays or multiplex PCR allow for the determination of the copy number of SMN-1 gene to identify heterozygous deletion, but these procedures are often time consuming and available on a limited clinical basis. Recently developed MLPA (multiplex ligation-dependent probe amplification) is an efficient procedure that can accurately analyze relative quantification to establish the copy number of the SMN gene. We performed a validation for simultaneous detection of homozygous SMN-1 deletions of SMA patients and heterozygous SMN-1 deletions of SMA carriers in a simple assay using a MLPA-SMA assay specific reagent. Results: Six out of 20 patients with SMA were found to have homozygous SMN-1 deletion, confirmed by the PCR/digestion assay. All 4 parents of the children with SMA had heterozygous SMN-1 deletion, confirmed by an independent relative quantitative analysis. Conclusion: MLPA provides a simple, rapid and accurate method of simultaneously detecting homozygous deletions and heterozygous deletions in a single assay for both SMN-1 and SMN-2 genes.
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应用多重连接探针扩增法简便高效检测Prader-Willi综合征的基因缺失
Objective: Prader-Willi syndrome (PWS) is characterized by severe hypotonia and feeding difficulties in early infancy, followed by excessive eating and gradual development of morbid obesity in later infancy or early childhood. Patients with PWS are often too young to manifest sufficient features or have atypical findings, making genetic testing important to confirm the diagnosis of PWS. Approximately 99% of patients with PWS have a diagnostic abnormality in the parent-specific methylation imprint within the Prader-Willi critical region (PWCR) at chromosome 15q11.2-q12. Of them, 70% have a paternal deletion; 25% have a maternal uniparental disomy (UPD); and <5% have a mutation in the imprinting center. Methods: Current techniques can identify a diagnostic abnormality, such as paternal deletion or maternal UPD for most of patients with PWS, but they are labor-intensive and cost-expensive. Multiplex ligation-dependent probe amplification (MLPA) is a novel, simple, and cost-effective technique for analysis of relative quantification in a single assay, which has recently been applied for the detection of genomic deletions, duplications, and amplifications in a variety of genes. Results: Six out of 20 patients referred for genetic diagnosis of PWS were found to have a deletion by MLPA, confirmed by FISH and DNA methylation analysis with 100% concordance. Conclusion: MLPA's high sensitivity and specificity for deletion detection is the same as FISH or Southern blot based analysis. Additional collaborative effort for developing and validating the complete MLPA-PWS assay, for not only detecting deletion but also identifying methylation abnormality, is on going.
关键词： Prader-Willi综合征 多重连接探针扩增法 基因缺失 遗传筛查 -
兄妹同患假肥大型肌营养不良症
目的 探讨同患假肥大型肌营养不良症(DMD)兄妹的临床以及实验室检查特点.方法 对患者进行临床观察、血清酶、肌电图、心电图及心脏彩色超声检查、肌肉病理HE染色,免疫组织化学染色检测肌肉组织抗肌萎缩蛋白、utrophin的表达,用多重连接探针扩增法对抗肌萎缩蛋白基因1～79号外显子进行缺失和/或重复突变检测,利用抗肌萎缩蛋白基因的CA短串联重复序列(STR)对该家系进行STR-PCR连锁分析.结果 兄妹二人符合DMD诊断,具有典型的DMD临床表现,肌酸激酶、肌酸激酶同工酶、乳酸脱氢酶、羟丁酸脱氢酶和谷草转氨酶的水平均显著高于正常值,肌电图呈肌源性损害,肌肉HE染色符合DMD,男患者的抗肌萎缩蛋白表达阴性,女患者的少量肌纤维仍可见不连续膜阳性,两患者抗肌萎缩蛋白基因的1～79号外显子未见缺失和重复突变,女患者与男患者携带相同的母源性X染色体.结论 携带DMD致病基因的女性携带者可以具有临床以及实验室的典型表现,应加强对携带者的全面检查.
关键词： 假肥大型肌营养不良症 女性 家系 抗肌萎缩蛋白 多重连接探针扩增法
