Northcott Neuroscience Laboratory, ANZAC Research Institute, Concord, New South Wales, Australia.
Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.
J Peripher Nerv Syst. 2022 Jun;27(2):120-126. doi: 10.1111/jns.12485. Epub 2022 Mar 5.
Biallelic mutations in sorbitol dehydrogenase (SORD) have been recently identified as a common cause of recessive axonal Charcot-Marie-Tooth neuropathy (CMT2). We aimed to assess a novel long-read sequencing approach to overcome current limitations in SORD neuropathy diagnostics due to the SORD2P pseudogene and the phasing of biallelic mutations in recessive disease. We conducted a screen of our Australian whole exome sequencing (WES) CMT cohort to identify individuals with homozygous or compound heterozygous SORD variants. Individuals detected with SORD mutations then underwent long-read sequencing, clinical assessment, and serum sorbitol analysis. An individual was detected with compound heterozygous truncating mutations in SORD exon 7, NM_003104.5:c.625C>T (p.Arg209Ter) and NM_003104.5:c.757del (p.Ala253GlnfsTer27). Subsequent Oxford Nanopore Tech (ONT) long-read sequencing was used to successfully differentiate SORD from the highly homologous non-functional SORD2P pseudogene and confirmed that the mutations were biallelic through haplotype-resolved analysis. The patient presented with axonal sensorimotor polyneuropathy (CMT2) and ulnar neuropathy without compression at the elbow. Burning neuropathic pain in the forearms and feet was also reported and was exacerbated by alcohol consumption and improved with alcohol cessation. UPLC-tandem mass spectrometry confirmed that the patient had elevated serum sorbitol levels (12.0 mg/L) consistent with levels previously observed in patients with biallelic SORD mutations. This represents a novel clinical presentation and expands the phenotype associated with biallelic SORD mutations causing CMT2. Our study is the first report of long-read sequencing for an individual with CMT and demonstrates the utility of this approach for clinical genomics.
最近发现,双等位基因突变 Sorbitol dehydrogenase (SORD) 是常染色体隐性遗传轴索型腓骨肌萎缩症 (CMT2) 的一个常见病因。我们旨在评估一种新的长读测序方法,以克服由于 SORD2P 假基因和隐性疾病中双等位基因突变的相位问题导致的 SORD 神经病诊断的当前局限性。我们对澳大利亚全外显子组测序 (WES) CMT 队列进行了筛查,以鉴定纯合子或复合杂合 SORD 变体的个体。发现 SORD 突变的个体随后进行长读测序、临床评估和血清山梨醇分析。发现个体在 SORD 外显子 7 中具有复合杂合截断突变,NM_003104.5:c.625C>T (p.Arg209Ter) 和 NM_003104.5:c.757del (p.Ala253GlnfsTer27)。随后使用 Oxford Nanopore Tech (ONT) 长读测序成功区分 SORD 和高度同源的非功能 SORD2P 假基因,并通过单倍型解析分析证实突变是双等位基因。该患者表现为轴索感觉运动性多发性神经病 (CMT2) 和肘部无压迫的尺神经病变。还报告了前臂和脚部灼痛性神经痛,饮酒会加重,戒酒会改善。UPLC-串联质谱证实患者的血清山梨醇水平升高 (12.0mg/L),与先前观察到的双等位基因突变患者的水平一致。这代表了一种新的临床表现,并扩展了与双等位基因突变导致 CMT2 相关的表型。我们的研究是首例使用长读测序对 CMT 患者进行的报告,并证明了该方法在临床基因组学中的应用。