Gap junctions are specialized matched membrane domains that contain channels that allow exchange of small molecules including ions, metabolites, and second messengers (e.g., Ca2+ and IP3) between neighboring cells. These channels are necessary for proper development and genetic linkage analyses have implicated connexins in at least 14 human diseases. The gap junction protein connexin43 (Cx43) is regulated via phosphorylation and its interactions with other proteins. This proposal focuses on the role that these two regulatory processes play and interplay in vivo to affect tissue development and function. We will examine the role Cx43 regulation plays during fundamental biological processes such as in the heart during ischemia, tachycardia and preconditioning, in skin during wound repair, and in the eye during development. We propose to (1) determine the consequences of specific Cx43 phosphorylation events on Cx43 function. (2) characterize changes in Cx43 phosphorylation and function in skin and heart in response to conditions such as wounding and hypoxia/ischemia., and (3) investigate the in vivo role of Cx43 phosphorylation in skin, heart, ovary, and eye at different developmental stages using knock-in mice expressing phosphorylation site mutants of Cx43. Understanding the linkage of changes in Cx43 phosphorylation to the exquisite control of fundamental biological events is in itself important but given that drugs to affect Cx43-related cardiac function and Cx43 anti-sense gels to speed wound healing are being tested in humans, we need to fully define these medically important biological events to better understand their implications and opportunities for patient treatment.