Short QT Syndrome or Andersen Syndrome

Abstract

See related article, pages 800–807 In 1994, the complete human cDNA of an inwardly rectifying K+ channel gene, KCNJ2 or Kir2.1, was isolated. Kir2.1 channels are important regulators of resting membrane potential of the cardiac (and also skeletal) muscle and cellular excitability,1 since they cause an outflow of K+ in the hyperpolarized membrane state during the terminal phase of cardiac action potential repolarization. The cDNA encodes a small protein of 427 amino acids with 2 putative transmembrane domains (M1, M2) and a pore region (H5) and regulates the inward rectifier K+ current I K1. Northern blot analysis demonstrated a 5.5-kb transcript with high levels in the heart, brain, placenta, lung, and skeletal muscle and lower levels in the kidney; in the heart, Kir2.1 channels are abundant in the atria, ventricle (with a high I K1 conductance) and Purkinje fibers, but less frequent in nodal cells. On current knowledge, 4 subunits form a functional (ie, tetrameric) channel, but they also may co-assemble with other subunits of the Kir2.x family as heteromultimers2 which indicates functional complexity and diversity. In 2001, Plaster …