TBX5 drives Scn5a expression to regulate cardiac conduction system function.
Cardiac conduction system (CCS) disease, which results in disrupted conduction and impaired cardiac rhythm, is common with significant morbidity and mortality. Current treatment options are limited, and rational efforts to develop cell-based and regenerative therapies require knowledge of the molecular networks that establish and maintain CCS function. Recent genome-wide association studies (GWAS) have identified numerous loci associated with adult human CCS function, including TBX5 and SCN5A. We hypothesized that TBX5, a critical developmental transcription factor, regulates transcriptional networks required for mature CCS function. We found that deletion of Tbx5 from the mature murine ventricular conduction system (VCS), including the AV bundle and bundle branches, resulted in severe VCS functional consequences, including loss of fast conduction, arrhythmias, and sudden death. Ventricular contractile function and the VCS fate map remained unchanged in VCS-specific Tbx5 knockouts. However, key mediators of fast conduction, including Nav1.5, which is encoded by Scn5a, and connexin 40 (Cx40), demonstrated Tbx5-dependent expression in the VCS. We identified a TBX5-responsive enhancer downstream of Scn5a sufficient to drive VCS expression in vivo, dependent on canonical T-box binding sites. Our results establish a direct molecular link between Tbx5 and Scn5a and elucidate a hierarchy between human GWAS loci that affects function of the mature VCS, establishing a paradigm for understanding the molecular pathology of CCS disease.
Department of Pediatrics, University of Chicago, Chicago, IL, USA.
David E
DE
Arnolds
Fang
F
Liu
John P
JP
Fahrenbach
Gene H
GH
Kim
Kurt J
KJ
Schillinger
Scott
S
Smemo
Elizabeth M
EM
McNally
Marcelo A
MA
Nobrega
Vickas V
VV
Patel
Ivan P
IP
Moskowitz
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging / Q000235:genetics / Q000503:physiopathology; D001665:Binding Sites; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D004562:Electrocardiography; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D055786:Gene Knockout Techniques; D006329:Heart Conduction System / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction; D062554:NAV1.5 Voltage-Gated Sodium Channel; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014463:Ultrasonography; D000097003:Gap Junction alpha-5 Protein
D017630:Connexins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D015222:Sodium Channels; D020825:T-Box Domain Proteins; D000097003:Gap Junction alpha-5 Protein; C568320:SCN5A protein, human; C568321:Scn5a protein, mouse; C103172:T-box transcription factor 5