Cx43, or Connexin 43, is a protein that forms gap junctions between cells, allowing for direct communication and the transfer of small molecules and ions. It plays a crucial role in various physiological processes, including heart function, where it helps coordinate the contraction of cardiac muscle cells. This protein is encoded by the GJA1 gene and is found in many tissues, including the heart, brain, and skin. Abnormalities in Cx43 expression or function can lead to various diseases, including cardiac arrhythmias and skin disorders, highlighting its importance in maintaining cellular health and communication.