Supplementary Material for: Premature Stroke Secondary to Severe Hypertension Results from Liddle Syndrome Caused by a Novel SCNN1B Mutation

Introduction: Liddle syndrome (LS), an autosomal dominant and inherited monogenic hypertension syndrome caused by pathogenic mutations in the epithelial sodium channel (ENaC) genes SCNN1A, SCNN1B, and SCNN1G. Objective: This study was designed to identify a novel SCNN1B missense mutation in a Chinese family with a history of stroke, and to confirm that the identified mutation is responsible for LS in this family. Methods: DNA samples were collected from the proband and 11 additional relatives. Next-generation sequencing was performed in the proband to find candidate variants. In order to exclude genetic polymorphism, the candidate variantin SCNN1B was verified in other family members, 100 hypertensives, and 100 healthy controls by Sanger sequencing. Results: Genetic testing revealeda novel and rare heterozygous variant in SCNN1B in the proband. This variant resulted in a substitution of threonine instead of proline at codon 617, altering the PY motif of β-ENaC. The identified mutation was only verified in 5 relatives. In silico analyses indicated that this variant was highly pathogenic. In this family, phenotypic heterogeneity was present among 6 LS patients. Tailored medicine with amiloride was effective in controlling hypertension and improving the serum potassium concentration in patients with LS. Conclusions:We identified a novel SCNN1B mutation (c.1849C>A) in a family affected by LS. Patients with LS, especially those with severe hypertension, should be alert for the occurrence of premature stroke. Timely diagnosis using genetic testing and tailored treatment with amiloride can help LS patients to avoid severe complications.

引言：利德尔综合征（Liddle syndrome, LS）是一种常染色体显性遗传性单基因高血压综合征，由上皮钠通道（epithelial sodium channel, ENaC）的SCNN1A、SCNN1B及SCNN1G基因的致病性突变引发。研究目的：本研究旨在鉴定一个伴有卒中家族史的中国家系中的新型SCNN1B错义突变，并确认该突变为本家系利德尔综合征的致病原因。研究方法：采集先证者及另外11名亲属的DNA样本。对先证者行二代测序（next-generation sequencing）以筛选候选变异。为排除遗传多态性，采用Sanger测序（Sanger sequencing）对该SCNN1B候选变异在其余家系成员、100名高血压患者及100名健康对照中进行验证。研究结果：基因检测显示先证者存在SCNN1B基因上一个新型罕见的杂合变异。该变异导致第617位密码子的脯氨酸被苏氨酸取代，改变了β-ENaC的PY基序。该突变仅在5名亲属中被检出。体外生物信息学分析（in silico analyses）表明该变异具有高度致病性。本家系中6名利德尔综合征患者存在表型异质性。采用阿米洛利的个体化治疗可有效控制利德尔综合征患者的高血压并改善血清钾浓度。研究结论：本研究在一个受累于利德尔综合征的家系中鉴定出新型SCNN1B突变（c.1849C>A）。利德尔综合征患者，尤其是重度高血压患者，应警惕早发性卒中的发生。通过基因检测及时诊断并采用阿米洛利行个体化治疗，可帮助利德尔综合征患者避免严重并发症。