Phenotypic feature and underlying mechanism of SLC4A3 variant associated short-QT syndrome in human induced pluripotent stem cell derived cardiomyocytes

Z. Meng (Mannheim)¹, B. Kovacs (Zürich)², C. Yan (Mannheim)¹, C. Hölscher (Mannheim)¹, O. Jarkas (Bochum)³, S. Zhazykbayeva (Bochum)⁴, L. Cyganek (Göttingen)⁵, N. Rehbehn (Mannheim)¹, F. Xuehui (Mannheim)¹, X. Lei (Mannheim)¹, R. Liu (Mannheim)¹, Z. Xue (Mannheim)¹, F. Duru (Zürich)², A. Aweimer (Bochum)⁶, A. Köppel (Heidelberg)⁷, K. Burau (Heidelberg)⁷, A. Mügge (Heidelberg)⁷, N. Hamdani (Bochum)⁸, W. Berger (Toronto)⁹, M. H. Gollob (Toronto)⁹, X. Zhou (Mannheim)¹, A. M. Saguner (Zürich)², I. Akin (Mannheim)¹, I. El-Battrawy (Bochum)^10
1Universitätsklinikum Mannheim GmbH I. Medizinische Klinik Mannheim, Deutschland; ²UniversitätsSpital Zürich Klinik für Kardiologie Zürich, Schweiz; ³Ruhr-Universität Bochum Bochum, Deutschland; ⁴Ruhr University Bochum Department of Cellular and Translational Physiology Bochum, Deutschland; ⁵Universitätsmedizin Göttingen Herzzentrum Göttingen - Stem Cell Unit Göttingen, Deutschland; ⁶Berufsgenossenschaftlliches Universitätsklinikum Bergmannsheil gGmbH Medizinische Klinik II, Kardiologie und Angiologie Bochum, Deutschland; ⁷Universitätsklinikum Heidelberg Institut für Humangenetik Heidelberg, Deutschland; ⁸Kath. Klinikum Bochum Cellular Physiology Bochum, Deutschland; ⁹University of Toronto Toronto, Kanada; ¹⁰Klinikum der Ruhr-Universität Bochum Medizinische Klinik II, Kardiologie Bochum, Deutschland

Aims: This study seeks to investigate the phenotypic characteristics and underlying pathogenic mechanisms associated with SQTS linked to variants in the SLC4A3 gene. Additionally, the study seeks to identify potential effective drugs for treating SLC4A3-related SQTS.

Methods: Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) generated from a patient with SQTS, who carried a variant in the SLC4A3 gene, as well as from a healthy donor (WT), an isogenic cell line with variant correction (using CRISPR/Cas9) were used, patch-clamp, Ca²⁺ imaging, single cell contraction, immunofluorescence, and molecular analyses were conducted for the study.

Results: Four family members presented with a shortened QT interval, with the proband experienced recurrent episodes of syncope. The total and membrane protein expression levels of the SLC4A3 were markedly reduced in SQTS-hiPSC-CMs, as evidenced by increased retention of  SLC4A3 within the endoplasmic reticulum. SQTS-hiPSC-CMs displayed a significantly shortened action potential duration (APD) and lower peak ICa-L current compared to WT and isogenic control cells. Unlike WT cells, which exhibited a frequency-dependent APD shortening, this adaptive response was absent in SQTS-hiPSC-CMs. A higher frequency of arrhythmia-like events detected in SQTS-hiPSC-CMs through recordings of spontaneous action potentials, calcium transient imaging, and single-cell contraction measurements. The elevated Na/Ca exchanger current (INCX) in SQTS-hiPSC-CMs may serve as a potential explanation for the higher incidence of delayed after depolarization (DAD) events observed. Quinidine and sotalol were found to prolong APD and decrease the occurrence of arrhythmic-like events in SQTS-hiPSC-CMs.

Conclusions: The SLC4A3 variant causes a loss-of-function in transporter activity and impaired cellular trafficking, leading to APD shortening; quinidine and sotalol may be effective drugs for SLC4A3-related SQTS.