Caballero Ricardo, Utrilla Raquel G, Amorós Irene, Matamoros Marcos, Pérez-Hernández Marta, Tinaquero David, Alfayate Silvia, Nieto-Marín Paloma, Guerrero-Serna Guadalupe, Liu Qing-Hua, Ramos-Mondragón Roberto, Ponce-Balbuena Daniela, Herron Todd, Campbell Katherine F, Filgueiras-Rama David, Peinado Rafael, López-Sendón José L, Jalife José, Delpón Eva, Tamargo Juan
Department of Pharmacology, School of Medicine, Instituto de Investigación Sanitaria Gregorio Marañón, Universidad Complutense, 28040 Madrid, Spain.
Centro de Investigación Biomédica en Red (CIBER), Spain.
Proc Natl Acad Sci U S A. 2017 Jan 17;114(3):E416-E425. doi: 10.1073/pnas.1612383114. Epub 2017 Jan 3.
Long QT syndrome (LQTS) exhibits great phenotype variability among family members carrying the same mutation, which can be partially attributed to genetic factors. We functionally analyzed the KCNH2 (encoding for Kv11.1 or hERG channels) and TBX20 (encoding for the transcription factor Tbx20) variants found by next-generation sequencing in two siblings with LQTS in a Spanish family of African ancestry. Affected relatives harbor a heterozygous mutation in KCNH2 that encodes for p.T152HfsX180 Kv11.1 (hERG). This peptide, by itself, failed to generate any current when transfected into Chinese hamster ovary (CHO) cells but, surprisingly, exerted "chaperone-like" effects over native hERG channels in both CHO cells and mouse atrial-derived HL-1 cells. Therefore, heterozygous transfection of native (WT) and p.T152HfsX180 hERG channels generated a current that was indistinguishable from that generated by WT channels alone. Some affected relatives also harbor the p.R311C mutation in Tbx20. In human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), Tbx20 enhanced human KCNH2 gene expression and hERG currents (I) and shortened action-potential duration (APD). However, Tbx20 did not modify the expression or activity of any other channel involved in ventricular repolarization. Conversely, p.R311C Tbx20 did not increase KCNH2 expression in hiPSC-CMs, which led to decreased I and increased APD. Our results suggest that Tbx20 controls the expression of hERG channels responsible for the rapid component of the delayed rectifier current. On the contrary, p.R311C Tbx20 specifically disables the Tbx20 protranscriptional activity over KCNH2 Therefore, TBX20 can be considered a KCNH2-modifying gene.
长QT综合征（LQTS）在携带相同突变的家庭成员中表现出很大的表型变异性，这部分可归因于遗传因素。我们对在一个非洲裔西班牙家庭中患有LQTS的两名兄弟姐妹中通过下一代测序发现的KCNH2（编码Kv11.1或hERG通道）和TBX20（编码转录因子Tbx20）变体进行了功能分析。受影响的亲属在KCNH2中存在一个杂合突变，该突变编码p.T152HfsX180 Kv11.1（hERG）。当该肽单独转染到中国仓鼠卵巢（CHO）细胞中时，未能产生任何电流，但令人惊讶的是，它在CHO细胞和小鼠心房来源的HL-1细胞中对天然hERG通道发挥了“伴侣样”作用。因此，天然（野生型，WT）和p.T152HfsX180 hERG通道的杂合转染产生的电流与仅由WT通道产生的电流无法区分。一些受影响的亲属在Tbx20中也存在p.R311C突变。在人诱导多能干细胞衍生的心肌细胞（hiPSC-CMs）中，Tbx20增强了人KCNH2基因的表达和hERG电流（I），并缩短了动作电位持续时间（APD）。然而，Tbx20并未改变参与心室复极的任何其他通道的表达或活性。相反，p.R311C Tbx20并未增加hiPSC-CMs中KCNH2的表达，这导致I降低和APD增加。我们的结果表明，Tbx20控制负责延迟整流电流快速成分的hERG通道的表达。相反，p.R311C Tbx20特异性地使Tbx20对KCNH2的转录前活性失活。因此，TBX20可被视为一个KCNH2修饰基因。
