Defective Tbx2-dependent patterning of the atrioventricular canal myocardium causes accessory pathway formation in mice

J Clin Invest. 2011 Feb;121(2):534-44. doi: 10.1172/JCI44350. Epub 2011 Jan 25.


Ventricular preexcitation, a feature of Wolff-Parkinson-White syndrome, is caused by accessory myocardial pathways that bypass the annulus fibrosus. This condition increases the risk of atrioventricular tachycardia and, in the presence of atrial fibrillation, sudden death. The developmental mechanisms underlying accessory pathway formation are poorly understood but are thought to primarily involve malformation of the annulus fibrosus. Before birth, slowly conducting atrioventricular myocardium causes a functional atrioventricular activation delay in the absence of the annulus fibrosus. This myocardium remains present after birth, suggesting that the disturbed development of the atrioventricular canal myocardium may mediate the formation of rapidly conducting accessory pathways. Here we show that myocardium-specific inactivation of T-box 2 (Tbx2), a transcription factor essential for atrioventricular canal patterning, leads to the formation of fast-conducting accessory pathways, malformation of the annulus fibrosus, and ventricular preexcitation in mice. The accessory pathways ectopically express proteins required for fast conduction (connexin-40 [Cx40], Cx43, and sodium channel, voltage-gated, type V, α [Scn5a]). Additional inactivation of Cx30.2, a subunit for gap junctions with low conductance expressed in the atrioventricular canal and unaffected by the loss of Tbx2, did not affect the functionality of the accessory pathways. Our results suggest that malformation of the annulus fibrosus and preexcitation arise from the disturbed development of the atrioventricular myocardium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Accessory Atrioventricular Bundle* / embryology
  • Accessory Atrioventricular Bundle* / pathology
  • Accessory Atrioventricular Bundle* / physiopathology
  • Animals
  • Atrioventricular Node* / embryology
  • Atrioventricular Node* / pathology
  • Atrioventricular Node* / physiopathology
  • Connexin 43 / genetics
  • Connexin 43 / metabolism
  • Female
  • Gene Expression Regulation, Developmental
  • Heart Conduction System* / embryology
  • Heart Conduction System* / pathology
  • Heart Conduction System* / physiopathology
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Morphogenesis*
  • Myocardium / cytology
  • Myocardium / metabolism
  • Pregnancy
  • T-Box Domain Proteins / genetics
  • T-Box Domain Proteins / metabolism*
  • Wolff-Parkinson-White Syndrome / pathology*
  • Wolff-Parkinson-White Syndrome / physiopathology*


  • Connexin 43
  • T-Box Domain Protein 2
  • T-Box Domain Proteins