Abstract
The cardiac conduction system (CCS) orchestrates the electrical impulses that enable coordinated contraction of the cardiac chambers. The T-box transcription factors TBX3 and TBX5 are required for cardiac conduction system development and associated with overlapping and distinct human cardiac conduction system diseases. We evaluated the coordinated role of Tbx3 and Tbx5 in the murine ventricular conduction system (VCS). We engineered a compound Tbx3:Tbx5 conditional knockout allele for both genes located in cis on mouse chromosome 5. Conditional deletion of both T-box transcriptional factors in the ventricular conduction system, using the VCS-specific Mink:Cre, caused loss of VCS function and molecular identity. Combined Tbx3 and Tbx5 deficiency in the adult VCS led to conduction defects, including prolonged PR and QRS intervals and elevated susceptibility to ventricular tachycardia. These electrophysiologic defects occurred prior to detectable alterations in cardiac contractility or histologic morphology, indicative of a primary conduction system defect. Tbx3:Tbx5 double knockout VCS cardiomyocytes revealed a transcriptional shift towards non-CCS-specialized working myocardium, suggesting reprogramming of their cellular identity. Furthermore, optical mapping revealed a loss of VCS-specific conduction system propagation. Collectively, these findings indicate that Tbx3 and Tbx5 coordinate to control VCS molecular fate and function, with implications for understanding cardiac conduction disorders in humans.
Competing Interest Statement
The authors have declared no competing interest.
Nonstandard Abbreviations and Acronyms
- ACUP
- animal care and use protocol
- AERP
- atrial effective refractory period
- A-H
- atrio-hisian interval
- APD50, 80
- action potential duration at 50 and 80% of repolarization
- AVB
- atrioventricular bundle
- AVERP
- atrioventricular nodal effective refractory period
- AVN
- atrioventricular node
- BBs
- bundle branches
- Cacna1d/Cav1.3
- calcium channel, voltage-dependent, L type, alpha 1D subunit
- Cacna1g/Cav3.1d
- calcium channel, voltage-dependent, T type, alpha 1G subunit
- Cacna1h/Cav3.2
- calcium channel, voltage-dependent, T type, alpha 1H subunit
- CCS
- cardiac conduction system
- Chr5
- chromosome 5
- Col1a1
- collagen, type I, alpha 1
- CREs
- cis-regulatory elements
- CRISPR
- clustered regularly interspaced short palindromic repeats
- EP studies
- electrophysiology studies
- ECG
- electrocardiography
- Eyfp
- enhanced yellow fluorescent protein
- FACS
- fluorescent-activated cell sorting
- FDR
- False Discovery Rate
- FS
- fractional shortening
- Gja1/Cx43
- gap junction protein, alpha 1
- Gja5/Cx40
- gap junction protein, alpha 5
- Gjc1/Cx45
- gap junction protein, gamma 1
- Gjd3/Cx30.2
- gap junction protein, delta 3
- GRN
- gene regulatory network
- GWAS
- genome wide association studies
- Hcn1
- hyperpolarization activated cyclic nucleotide gated potassium channel 1
- Hcn4
- hyperpolarization-activated, cyclic nucleotide-gated K+ 4
- Hd
- his-duration
- HOS
- Holt-Oram syndrome
- H-V
- hisio-ventricular interval
- IACUC
- institutional animal care and use committee
- Kcne1/MinK
- potassium voltage-gated channel, Isk-related subfamily, member 1
- Kcnj2/Kir2.1
- potassium inwardly-rectifying channel, subfamily J, member 2
- Kcnj3/Kir3.1
- potassium inwardly-rectifying channel, subfamily J, member 3
- Kcnj4/IRK3
- potassium inwardly-rectifying channel, subfamily J, member 4
- Kcnj12/Kir2.2
- potassium inwardly-rectifying channel, subfamily J, member 12
- Kcnk3/Task-1
- potassium channel, subfamily K, member 3
- lssDNA donor
- long single-stranded DNA donor
- LVEF
- left ventricular ejection fraction
- OAP
- optical action potential
- OE
- overexpression
- OMIM
- online Mendelian inheritance in man
- QRS
- QRS complex
- QT
- QT-interval duration
- PAM sequence
- protospacer-adjacent motif sequence
- Postn
- periostin, osteoblast specific factor
- PR
- PR-interval duration
- RFLP
- Restriction fragment length polymorphism
- RR
- RR-interval duration
- Ryr2
- ryanodine receptor 2, cardiac
- SAN
- sinoatrial node
- Scn5a/Nav1.5
- sodium channel, voltage-gated, type V, alpha
- sgRNA
- single guide RNA
- Smpx
- small muscle protein, X-linked
- Tbx3
- T-box 3
- Tbx5
- T-box 5
- TM
- tamoxifen
- VCS
- ventricular conduction system
- VERP
- ventricular effective refractory period
- VT
- ventricular tachycardia
