Homeobox protein Hop functions in the adult cardiac conduction system

Circ Res. 2005 Apr 29;96(8):898-903. doi: 10.1161/01.RES.0000163108.47258.f3. Epub 2005 Mar 24.


Hop is an unusual homeobox gene expressed in the embryonic and adult heart. Hop acts downstream of Nkx2-5 during development, and Nkx2-5 mutations are associated with cardiac conduction system (CCS) defects. Inactivation of Hop in the mouse is lethal in half of the expected null embryos. Here, we show that Hop is expressed strongly in the adult CCS. Hop-/- adult mice display conduction defects below the atrioventricular node (AVN) as determined by invasive electrophysiological testing. These defects are associated with decreased expression of connexin40. Our results suggest that Hop functions in the adult CCS and demonstrate conservation of molecular hierarchies between embryonic myocardium and the specialized conduction tissue of the mature heart.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Connexins / analysis
  • Electrocardiography
  • Heart Conduction System / physiology*
  • Homeobox Protein Nkx-2.5
  • Homeodomain Proteins / physiology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Transcription Factors / physiology


  • Connexins
  • Homeobox Protein Nkx-2.5
  • Homeodomain Proteins
  • Hop protein, mouse
  • Nkx2-5 protein, mouse
  • Transcription Factors
  • connexin 40