Non-missense variants of KCNH2 show better outcomes in Type 2 Long QT Syndrome

1. Mizusawa Y, Horie M, Wilde AA. Genetic and clinical advances in congenital long QT

syndrome. Circ J 2014;78:2827–33.

2. Schwartz PJ, Crotti L, Insolia R. Long-QT syndrome: from genetics to management. Circ

Arrhythm Electrophysiol 2012;5:868–77.

3. Tester DJ, Will ML, Haglund CM, Ackerman MJ. Effect of clinical phenotype on yield of

long QT syndrome genetic testing. J Am Coll Cardiol 2006;47:764–8.

4. Schwartz PJ, Ackerman MJ, George AL Jr, Wilde AAM. Impact of genetics on the clinical

management of channelopathies. J Am Coll Cardiol 2013;62:169–80.

5. Splawski I, Shen J, Timothy KW, Lehmann MH, Priori S, Robinson JL et al. Spectrum of

mutations in long-QT syndrome genes. KVLQT1, HERG, SCN5A, KCNE1, and KCNE2.

Circulation 2000;102:1178–85.

6. Ono M, Burgess DE, Schroder EA, Elayi CS, Anderson CL, January CT et al. Long QT

syndrome type 2: emerging strategies for correcting class 2 KCNH2 (hERG) mutations

and identifying new patients. Biomolecules 2020;10:1144.

7. Gong Q, Zhang L, Vincent GM, Horne BD, Zhou Z. Nonsense mutations in hERG cause

a decrease in mutant mRNA transcripts by nonsense-mediated mRNA decay in human

long-QT syndrome. Circulation 2007;116:17–24.

8. Gong Q, Stump MR, Zhou Z. Position of premature termination codons determines

susceptibility of hERG mutations to nonsense-mediated mRNA decay in long QT syndrome. Gene 2014;539:190–7.

9. Bhuiyan ZA, Momenah TS, Gong Q, Amin AS, Ghamdi SA, Carvalho JS et al. Recurrent

intrauterine fetal loss due to near absence of HERG: clinical and functional characterization of a homozygous nonsense HERG Q1070X mutation. Heart Rhythm 2008;5:

553–61.

10. Shimizu W, Moss AJ, Wilde AA, Towbin JA, Ackerman MJ, January CT et al.

Genotype-phenotype aspects of type 2 long QT syndrome. J Am Coll Cardiol 2009;

54:2052–62.

11. Zarraga IG, Zhang L, Stump MR, Gong Q, Vincent GM, Zhou Z. Nonsense-mediated

mRNA decay caused by a frameshift mutation in a large kindred of type 2 long QT syndrome. Heart Rhythm 2011;8:1200–6.

12. Doyle DA, Morais Cabral J, Pfuetzner RA, Kuo A, Gulbis JM, Cohen SL et al. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science

1998;280:69–77.

13. Morais Cabral JH, Lee A, Cohen SL, Chait BT, Li M, Mackinnon R. Crystal structure and

functional analysis of the HERG potassium channel N terminus: a eukaryotic PAS domain. Cell 1998;95:649–55.

14. Brelidze TI, Gianulis EC, DiMaio F, Trudeau MC, Zagotta WN. Structure of the

C-terminal region of an ERG channel and functional implications. Proc Natl Acad Sci

U S A 2013;110:11648–53.

15. Moss AJ, Zareba W, Kaufman ES, Gartman E, Peterson DR, Benhorin J et al. Increased

risk of arrhythmic events in long-QT syndrome with mutations in the pore region

of the human ether-a-go-go-related gene potassium channel. Circulation 2002;105:

794–9.

16. Anderson CL, Delisle BP, Anson BD, Kilby JA, Will ML, Tester DJ et al. Most LQT2 mutations reduce Kv11.1 (hERG) current by a class 2 (trafficking-deficient) mechanism.

Circulation 2006;113:365–73.

17. Anderson CL, Kuzmicki CE, Childs RR, Hintz CJ, Delisle BP, January CT. Large-scale mutational analysis of Kv11.1 reveals molecular insights into type 2 long QT syndrome. Nat

Commun 2014;5:5535.

18. Gong Q, Keeney DR, Molinari M, Zhou Z. Degradation of trafficking-defective long QT

syndrome type II mutant channels by the ubiquitin-proteasome pathway. J Biol Chem

2005;280:19419–25.

19. Foo B, Barbier C, Guo K, Vasantharuban J, Lukacs GL, Shrier A. Mutation-specific peripheral and ER quality control of hERG channel cell-surface expression. Sci Rep 2019;9:

6066.

20. Ohno S, Ozawa J, Fukuyama M, Makiyama T, Horie M. An NGS-based genotyping in

LQTS; minor genes are no longer minor. J Hum Genet 2020;65:1083–91.

21. Schwartz PJ, Stramba-Badiale M, Crotti L, Pedrazzini M, Besana A, Bosi G et al.

Prevalence of the congenital long-QT syndrome. Circulation 2009;120:

1761–7.

22. Richards S, Aziz N, Bale S, Bick D, Das S, Gastier-Foster J et al. Standards and guidelines

for the interpretation of sequence variants: a joint consensus recommendation of the

American College of Medical Genetics And Genomics and the Association for

Molecular Pathology. Genet Med 2015;17:405–24.

23. Wang W, MacKinnon R. Cryo-EM structure of the open human ether-à-go-go-related

K+ channel hERG. Cell 2017;169:422–430.e10.

24. Vink AS, Neumann B, Lieve KVV, Sinner MF, Hofman N, El Kadi S et al. Determination

and interpretation of the QT interval. Circulation 2018;138:2345–58.

25. Rijnbeek PR, Witsenburg M, Schrama E, Hess J, Kors JA. New normal limits for the

paediatric electrocardiogram. Eur Heart J 2001;22:702–11.

26. Schwartz PJ, Ackerman MJ, Antzelevitch C, Bezzina CR, Borggrefe M, Cuneo BF et al.

Inherited cardiac arrhythmias. Nat Rev Dis Primers 2020;6:58.

27. Ozawa J, Ohno S, Hisamatsu T, Itoh H, Makiyama T, Suzuki H et al. Pediatric cohort with

long QT syndrome- KCNH2 mutation carriers present late onset but severe symptoms.

Circ J 2016;80:696–702.

Downloaded from https://academic.oup.com/europace/advance-article/doi/10.1093/europace/euac269/7067295 by Kyoto University user on 05 March 2023

or without WT subunits, revealing that the PD-mediated DN was caused

through Class 2 rather than Class 3 or 4 mechanisms. In contrast, other

missense variants may cause HI by Class 2 mechanism without affecting

the transport of WT subunit.

In this study with many LQT2 patients, the prediction of

loss-of-function mechanisms by functional domains (Figure 2C) was

found to be helpful for assessing the prognosis. These dominant functional effects in each domain (Figure 3) showed accordance with their

severity of clinical characteristics (see Supplementary material online,

Table S4). Furthermore, our data support for the first time that transmembrane domains including not only PD but VSD presented poorer

clinical outcomes than others. In the literature, 12 of 18 previously studied variants in the VSD exerted a DN phenotype (Figure 3), and in our

cohort, 15 carriers with variants in the VSD showed severe phenotypes

(see Supplementary material online, Table S4).

T. Aizawa et al.

Clinical outcomes of non-missense variants of KCNH2

32. Ficker E, Dennis AT, Obejero-Paz CA, Castaldo P, Taglialatela M, Brown AM. Retention

in the endoplasmic reticulum as a mechanism of dominant-negative current suppression

in human long QT syndrome. J Mol Cell Cardiol 2000;32:2327–37.

33. Huo J, Zhang Y, Huang N, Liu P, Huang C, Guo X et al. The G604S-hERG mutation alters

the biophysical properties and exerts a dominant-negative effect on expression of hERG

channels in HEK293 cells. Pflugers Arch 2008;456:917–28.

34. Zhao JT, Hill AP, Varghese A, Cooper AA, Swan H, Laitinen-Forsblom PJ et al. Not all

hERG pore domain mutations have a severe phenotype: G584S has an inactivation

gating defect with mild phenotype compared to G572S, which has a dominant negative trafficking defect and a severe phenotype. J Cardiovasc Electrophysiol 2009;20:

923–30.

Downloaded from https://academic.oup.com/europace/advance-article/doi/10.1093/europace/euac269/7067295 by Kyoto University user on 05 March 2023

28. Therneau TM, Grambsch PM. The cox model. In: Therneau TM and Grambsch PM

(eds.), Modeling Survival Data: Extending the Cox Model. Statistics for Biology and Health.

1st ed. Heidelberg, Germany: Springer; 2000. p39–79.

29. Moss AJ, Shimizu W, Wilde AA, Towbin JA, Zareba W, Robinson JL et al. Clinical aspects

of type-1 long-QT syndrome by location, coding type, and biophysical function of mutations involving the KCNQ1 gene. Circulation 2007;115:2481–9.

30. Fukuyama M, Horie M, Aoki H, Ozawa J, Kato K, Sawayama Y et al. School-based routine

screenings of electrocardiograms for the diagnosis of long QT syndrome. Europace

2022;24:1496–1503.

31. Delisle BP, Anson BD, Rajamani S, January CT. Biology of cardiac arrhythmias: ion channel protein trafficking. Circ Res 2004;94:1418–28.

...