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目的:探索无创产前检测(NIPT)脊髓性肌肉萎缩症(SMA)在临床应用的可行性。方法:招募生育过SMA先证者且再次妊娠的24个家系,其家系中夫妻双方及先证者致病突变经多重连接探针扩增技术(MLPA)测定。采集家系外周血及孕11周以后的孕妇血浆,通过目标序列捕获及高通量测序技术,首先对夫妻双方及先证者外周血DNA样品进行目标区域捕获测序,获得与致病位点连锁的亲本单体型信息,再结合血浆测序数据中提供的单核苷酸多态性位点的分析结果,构建隐马尔可夫模型,推断胎儿单体型,从而得到胎儿的基因型。同时利用有创产前诊断MLPA检测验证其准确性。本次研究主要针对SMN1基因第7、8号外显子的检测。结果:24个家系通过NIPT检测检出患胎5例,携带者7例,余12例正常;MLPA检测结果为5例患胎,8例携带者,11例正常。患胎均为SMN1基因第7、8号外显子纯合缺失。NIPT与MLPA检测结果一致率为95.83%(23/24),两种方法诊断结果差异无统计学意义(P=0.317)。结论:基于母体血浆目标区域捕获测序、单体型分析NIPT胎儿SMA风险的方法准确、安全,应用于有先证者遗传信息的SMA NIPT有一定可行性。
Objective: To explore the feasibility of noninvasive prenatal detection (NIPT) spinal muscular atrophy (SMA) in clinical application. METHODS: Twenty-four pedigrees with fertilized SMA probands who were pregnant again were enrolled in this study. Pathogenesis mutations in both spouses and probands in their pedigrees were determined by multiplex ligation probe amplification (MLPA). Blood samples of peripheral blood of pregnant women and pregnant women after 11 weeks of gestation were collected. Sequencing by target sequence and high-throughput sequencing technology, the target region was captured and sequenced from the peripheral DNA samples of both spouses and probands. Parental haplotype information, combined with the analysis of single nucleotide polymorphism sites provided in the plasma sequencing data to construct a hidden Markov model to infer the fetus haplotype, thereby obtaining the fetal genotype. At the same time using invasive prenatal diagnosis of MLPA test to verify its accuracy. This study mainly focused on the detection of SMN1 exons 7,8. Results: Twenty-four pedigrees were detected with NIPT in 5 cases and 7 cases with carriers, the remaining 12 cases were normal. The MLPA test results were 5 cases of fetuses, 8 cases of carriers and 11 cases of normal. The fetuses were homozygous deletion of exon 7 and exon 8 of SMN1 gene. The agreement between NIPT and MLPA was 95.83% (23/24). There was no significant difference between the two methods (P = 0.317). CONCLUSIONS: Based on maternal plasma target capture sequencing, the method of haplotype analysis of SMA risk in NIPT fetuses is accurate and safe and may be applied to SMA NIPT with genetic information of probands.