Preclinical evidence for the therapeutic value of TBX5 normalization in arrhythmia control

Abstract

Aims Arrhythmias and sudden cardiac death (SCD) occur commonly in patients with heart failure. We found T-box 5 (TBX5) dysregulated in ventricular myocardium from heart failure patients and thus we hypothesized that TBX5 reduction contributes to arrhythmia development in these patients. To understand the underlying mechanisms, we aimed to reveal the ventricular TBX5-dependent transcriptional network and further test the therapeutic potential of TBX5 level normalization in mice with documented arrhythmias. Methods and Results We used a mouse model of TBX5 conditional deletion in ventricular cardiomyocytes. Ventricular (v) TBX5 loss in mice resulted in mild cardiac dysfunction and arrhythmias and was associated with a high mortality rate (60%) due to SCD. Upon angiotensin stimulation, vTbx5KO mice showed exacerbated cardiac remodelling and dysfunction suggesting a cardioprotective role of TBX5. RNA sequencing of a ventricular specific TBX5KO mouse and TBX5 chromatin immunoprecipitation were used to dissect TBX5 transcriptional network in cardiac ventricular tissue. Overall, we identified 47 transcripts expressed under the control of TBX5, which may have contributed to the fatal arrhythmias in vTbx5KO mice. These included transcripts encoding for proteins implicated in cardiac conduction and contraction (Gja1, Kcnj5, Kcng2, Cacna1g, Chrm2), in cytoskeleton organization (Fstl4, Pdlim4, Emilin2, Cmya5), and cardiac protection upon stress (Fhl2, Gpr22, Fgf16). Interestingly, after TBX5 loss and arrhythmia development in vTbx5KO mice, TBX5 protein level normalization by systemic adeno-associated-virus (AAV) 9 application, re-established TBX5-dependent transcriptome. Consequently, cardiac dysfunction was ameliorated and the propensity of arrhythmia occurrence was reduced. Conclusions This study uncovers a novel cardioprotective role of TBX5 in the adult heart and provides preclinical evidence for the therapeutic value of TBX5 protein normalization in the control of arrhythmia. Translational perspective Cardiovascular disease (CVD) is the number one cause of death worldwide (WHO factsheets 09/2016). Although more than 60% of CVD-related deaths are due to out-of-hospital sudden cardiac death (SCD), we have little insight in the mechanisms underlying SCD pathophysiology. Our data show a link between TBX5 dysregulation and arrhythmia occurrence in patients. To test the therapeutic potential of TBX5, we normalized TBX5 levels in a mouse model with TBX5 dysregulation, which developed arrhythmias and SCD. TBX5 normalization re-established TBX5 target gene expression and more importantly, rescued the arrhythmia phenotype. Altogether, we provide proof-of-concept for the therapeutic potential of TBX5 expression restoration against arrhythmia and SCD.

Return of the Tbx5; lineage-tracing reveals ventricular cardiomyocyte-like precursors in the injured adult mammalian heart

“…The fact that this is a BAC insert, allows for investigating the spatiotemporal expression of Tbx5 in the adult heart, without inducing a cardiac phenotype 23 . Importantly, our transgene is capable of lineage-tracing mostly ventricular Tbx5-expressing cardiac cells, which may be important for ventricle-specific repair/regeneration, in-line with recent published basic research and preclinical data 64–66 . In our study, Tbx5 re-activated CMs were located close to the lesion areas, but a few were also observed in non-injured areas of the adult heart.…”

“…The fact that this is a BAC insert, allows for investigating the spatiotemporal expression of Tbx5 in the adult heart, without inducing a cardiac phenotype 23 . Importantly, our transgene is capable of lineage-tracing mostly ventricular Tbx5-expressing cardiac cells, which may be important for ventricle-specific repair/regeneration, in-line with recent published basic research and preclinical data [64][65][66] In humans, TBX5 is expressed in both the embryonic and adult four-chambered heart, in yet unidentified cardiac cell populations 67 . In the adult mouse, Tbx5 has been shown to be primarily expressed in the atria but not in the ventricles, in the absence of injury, which we also observed 43 .…”

In vivo identification and validation of novel potential predictors for human cardiovascular diseases

“…The five positive controls, known to play key roles in heart functions such as cardiac contraction ( TTN [ 59 ] and NACA [ 60 ]) and heart rate regulation ( CASQ2 [ 61 ], KCNH2 [ 62 ] and SCN5A [ 63 , 64 ]) clearly responded in the assay. Beyond known cardiac genes, we revealed new genes linked to various biological functions ( CCDC141 , GIGYF1 , HOMEZ , MYRF , SMG6 , CMYA5 , CNOT1 , SLC17A3 , TRAPPC12 , SSPO and PADI4 ) which up to now, had little to no experimental evidence in cardiac function [ 65 – 68 ].…”

In vivoidentification and validation of novel potential predictors for human cardiovascular diseases

“…Across the hGWAS set of 40 genes, comparative heart rate analysis showed statistically significant heart rate phenotypes in a total of 16 genes ( Fig 3B). The five positive controls, known to play key roles in heart functions such as cardiac contraction (TTN and NACA) and heart rate regulation (CASQ2, Beyond known cardiac genes, we revealed new genes linked to various biological functions (CCDC141, GIGYF1, HOMEZ, MYRF, SMG6, CMYA5, CNOT1, SLC17A3, TRAPPC12, SSPO and PADI4) which up to now, had little to no experimental evidence in cardiac function (Rathjens et al 2020;Benson et al 2017;Yamaguchi et al 2018;Elmen et al 2020).…”

“…clearly responded in the assay. Beyond known cardiac genes, we revealed new genes linked to various biological functions (CCDC141, GIGYF1, HOMEZ, MYRF, SMG6, CMYA5, CNOT1, SLC17A3, TRAPPC12, SSPO and PADI4) which up to now, had little to no experimental evidence in cardiac function (Rathjens et al 2020;Benson et al 2017;Yamaguchi et al 2018;Elmen et al 2020).…”