Mechanisms of Segmentation, Septation, and Remodeling of the Tubular Heart
1999; Elsevier BV; Linguagem: Inglês
10.1016/b978-012329860-7/50012-x
AutoresCorey H. Mjaatvedt, Hideshi Yamamura, Andy Wessels, Anne Ramsdell, Debi Turner, Roger R. Markwald,
Tópico(s)Cancer-related gene regulation
ResumoThe formation and differentiation of the endocardial cushions and the process of heart looping are central events required for the reorganization of the single heart tube into a four-chambered structure. Both these events are regulated by the segmental restriction of gene expression along the anterior-posterior axis of the heart tube. Because of segmental restrictions, it is proposed that the endocardial cushions form in only two regions of the tube. The initial rightward bend of the tube separates the first two segments into the initial inlet and outlet of the primitive heart. The completion of looping, which accompanies remodeling, brings the inlet and outlet segments of the tube into their correct anatomical relationship and alignment. The endocardial cushions then have multiple functions: to divide the inlet into a right and left side; to form the valvular leaflets through the growth and differentiation of the cushion's luminal surface; and to induce myocardialization that removes the myocardium from the inner curvature of the heart, bringing the internal septa into alignment. Thus, any perturbations that restrict the growth and/or normal differentiation of the cushions could be expected to give rise to a common defective phenotype. This may explain why a wide variety of environmental insults and a diverse assortment of gene mutations can result in a similar spectrum of inlet and outlet heart defects.
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