Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China; National Center for Neurological Disorders, Shanghai, China; Huashan Rare Disease Center, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.
Department of Neurology and Institute of Neurology of First Affiliated Hospital, Institute of Neuroscience, and Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China.
J Mol Diagn. 2024 May;26(5):364-373. doi: 10.1016/j.jmoldx.2024.02.004. Epub 2024 Mar 13.
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder primarily caused by the deletion or mutation of the survival motor neuron 1 (SMN1) gene. This study assesses the diagnostic potential of long-read sequencing (LRS) in three patients with SMA. For Patient 1, who has a heterozygous SMN1 deletion, LRS unveiled a missense mutation in SMN1 exon 5. In Patient 2, an Alu/Alu-mediated rearrangement covering the SMN1 promoter and exon 1 was identified through a blend of multiplex ligation-dependent probe amplification, LRS, and PCR across the breakpoint. The third patient, born to a consanguineous family, bore four copies of hybrid SMN genes. LRS determined the genomic structures, indicating two distinct hybrids of SMN2 exon 7 and SMN1 exon 8. However, a discrepancy was found between the SMN1/SMN2 ratio interpretations by LRS (0:2) and multiplex ligation-dependent probe amplification (0:4), which suggested a limitation of LRS in SMA diagnosis. In conclusion, this newly adapted long PCR-based third-generation sequencing introduces an additional avenue for SMA diagnosis.
脊髓性肌萎缩症（SMA）是一种常染色体隐性神经肌肉疾病，主要由生存运动神经元 1（SMN1）基因的缺失或突变引起。本研究评估了长读测序（LRS）在 3 名 SMA 患者中的诊断潜力。对于杂合性 SMN1 缺失的患者 1，LRS 揭示了 SMN1 外显子 5 的错义突变。在患者 2 中，通过多重连接依赖性探针扩增、LRS 和跨断点的 PCR 混合，发现了涉及 SMN1 启动子和外显子 1 的 Alu/Alu 介导的重排。第三位患者出生于近亲家庭，携带四个混合 SMN 基因拷贝。LRS 确定了基因组结构，表明 SMN2 外显子 7 和 SMN1 外显子 8 存在两种不同的杂交体。然而，LRS（0:2）和多重连接依赖性探针扩增（0:4）对 SMN1/SMN2 比值的解释存在差异，这表明 LRS 在 SMA 诊断中存在局限性。总之，这种新适应的基于长 PCR 的第三代测序为 SMA 诊断提供了另一种途径。
