Agnes Ginges Centre for Molecular Cardiology Centenary Institute, The University of Sydney, Australia (E.S.S., J.I., C.S., R.D.B.).
Faculty of Medicine and Health, The University of Sydney, Australia (J.I., C.S., R.D.B.).
Circ Genom Precis Med. 2019 Jan;12(1):e002368. doi: 10.1161/CIRCGEN.118.002368.
MYBPC3 splicing errors are a common cause of hypertrophic cardiomyopathy (HCM). Variants affecting essential splice-site dinucleotides inhibit splicing, whereas the impact of variants at conserved flanking nucleotides is less clear. We evaluated the contribution of MYBPC3 splice-site variants in a large cohort of patients with HCM and assessed the impact on splicing with RNA analysis.
Patients attending a specialized multidisciplinary clinic, with a clinical diagnosis of HCM and genetic testing of at least 46 cardiomyopathy-associated genes, were included. Patients with variants in MYBPC3 splice sites with in silico-predicted effects on splicing were selected. RNA was extracted from fresh venous blood or paraffin-embedded myocardial tissue of the patients, amplified, and sequenced. Variants were classified for pathogenicity using the American College of Medical Genetics and Genomics guidelines.
We found 29 rare MYBPC3 splice-site variants in 56 of 557 (10%) unrelated HCM probands. Three variants were not predicted to alter RNA splicing, and 13 essential splice dinucleotide, nonsense, and short insertion or deletion variants were not further assessed. RNA analysis was performed on 9 variants (c.654+5G>C, c.772G>A, c.821+3G>T, c.927-9G>A, c.1090G>A, c.1624G>A, c.1624+4A>T, c.3190+5G>A, and c.3491-3C>G), and RNA splicing errors were confirmed for 7. Four variants in 4 families resulted in clinically meaningful reclassifications.
After RNA analysis, 4 of 56 (7%) families with MYBPC3 splice-site variants were reclassified from uncertain clinical significance to likely pathogenic. RNA analysis of splice-site variants can assist in understanding pathogenicity and increase the diagnostic yield of genetic testing in HCM.
肌球蛋白结合蛋白 C3（MYBPC3）剪接错误是肥厚型心肌病（HCM）的常见病因。影响关键剪接位点二核苷酸的变异会抑制剪接，而保守侧翼核苷酸变异的影响则不太清楚。我们评估了 MYBPC3 剪接位点变异在一大组 HCM 患者中的作用，并通过 RNA 分析评估其对剪接的影响。
我们纳入了在专门的多学科诊所就诊的、具有 HCM 临床诊断且至少接受了 46 种心肌病相关基因遗传检测的患者。选择具有预测对剪接有影响的 MYBPC3 剪接位点变异的患者。从患者的新鲜静脉血或石蜡包埋心肌组织中提取 RNA，进行扩增和测序。根据美国医学遗传学与基因组学学院的指南对变异进行致病性分类。
我们在 557 名无关 HCM 先证者中发现了 29 种罕见的 MYBPC3 剪接位点变异，发生率为 10%。其中 3 种变异未被预测会改变 RNA 剪接，13 种关键剪接二核苷酸、无义、短插入或缺失变异未进一步评估。对 9 种变异（c.654+5G>C、c.772G>A、c.821+3G>T、c.927-9G>A、c.1090G>A、c.1624G>A、c.1624+4A>T、c.3190+5G>A 和 c.3491-3C>G）进行了 RNA 分析，并证实了 7 种存在 RNA 剪接错误。4 个家系中的 4 种变异导致了有临床意义的重新分类。
经过 RNA 分析，56 个 MYBPC3 剪接位点变异家系中有 4 个（7%）从不确定的临床意义重新分类为可能致病性。对剪接位点变异进行 RNA 分析有助于理解致病性，并提高 HCM 基因检测的诊断率。
