Immunofluorescent localization of tenascin during the morphogenesis of the outflow tract of the chick embryo heart.

The cono-truncus constitutes a complex segment of the developing heart that gives rise to the outflow tract of the ventricles and root of the pulmonary and aortic arteries. Numerous studies have revealed that the extracellular matrix plays a relevant role in most morphogenetic processes modulating cell behaviour. By means of immunofluorescence, we studied the distribution and possible involvement of tenascin during morphogenesis of the conus and truncus in chick embryo hearts between days 4.5-10 of incubation. Tenascin is an extracellular matrix glycoprotein with a significant role in morphogenesis and cell and tissue differentiation. Our results reveal a specific distribution of tenascin in the areas of the cono-truncus undergoing significant structural changes during morphogenesis of this cardiac segment, appearing mainly in the mesenchymal layer subjacent to the myocardial layer, the cono-truncal ridges and the aorto-pulmonary septum. The distribution of tenascin was compared and contrasted with that of collagen type I, which constitutes a further component of the extracellular matrix common to most developing connective tissues.