Molecular and functional maturation of the murine cardiac conduction system.

The rhythmic heartbeat reflects a highly coordinated electrical wave, initiated and propagated throughout the myocardium by the specialized cardiac conduction system (CCS). Conduction system abnormalities affect millions of individuals, with symptoms from merely bothersome palpitations to fainting or even sudden death. Despite years of investigation, knowledge of the genes and molecules that direct CCS development and function are incomplete. In 1977, Viragh and Challice published the first in a series of articles describing the morphologic development of the murine CCS. The framework established by those reports now can be revisited in light of recent data. Imaging the developing CCS-using genetically engineered mice combined with functional assays, including optical mapping of cardiac electrical excitation-reveal some of the earliest events in CCS formation and function. These findings build on the experiments of Viragh and Challice, leading to a more integrated picture of conduction system development in the mammalian embryo.