Quantification of myocyte chemotaxis: a role for FAK in regulating directional motility.

Formation of a fully functional four-chambered heart involves an intricate and complex series of events that includes precise spatial-temporal regulation of cell specification, proliferation, and migration. The formation of the ventricular septum during mid-gestation ensures the unidirectional flow of blood, and is necessary for postnatal viability. Notably, a majority of all congenital malformations of the cardiovascular system in humans involve septal abnormalities which afflict 1 out of 100 newborn children in the United States. Thus, a clear understanding of the precise mechanisms involved in this morphogenetic event will undoubtedly reveal important therapeutic targets. The final step in valvuloseptal morphogenesis occurs, in part, by directed movement of flanking myocytes into the cushion mesenchyme. In order to identify the molecular mechanisms that regulate this critical myocyte function, we have developed two in vitro methodologies; a transwell assay to assess population changes in motility and a single-cell tracking assay to identify signals that drive the coordinated movement of these cells. These methods have proven effective to identify focal adhesion kinase (FAK) as an intracellular component that is critical for myocyte chemotaxis.