Connexins on the other hand play a vital role in physical cell-cell communication, as well as being associated with cell phenotype: Cx-45 has dominantly been detected in the conductive tissue, whilst Cx-40 and/or Cx-43 are expressed in adult working myocardium (atrial and ventricular CMs), with a reduced expression (number and location) of connexins reported in MI and heart failure [52]. This evidence concerns the gene GJA5 and heart failure.