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Deprecated: Implicit conversion from float 225.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534 BMC+Dev+Biol 2015 ; 15 (ä): ä Nephropedia Template TP
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Muscleblind-like 1 is required for normal heart valve development in vivo #MMPMID26472242
BMC Dev Biol 2015[]; 15 (ä): ä PMID26472242show ga
Background: Development of the valves and septa of the heart depends on the formation and remodeling of the endocardial cushions in the atrioventricular canal and outflow tract. These cushions are populated by mesenchyme produced from the endocardium by epithelial-mesenchymal transition (EMT). The endocardial cushions are remodeled into the valves at post-EMT stages via differentiation of the mesenchyme and changes in the extracellular matrix (ECM). Transforming growth factor ? (TGF?) signaling has been implicated in both the induction of EMT in the endocardial cushions and the remodeling of the valves at post-EMT stages. We previously identified the RNA binding protein muscleblind-like 1 (MBNL1) as a negative regulator of TGF? signaling and EMT in chicken endocardial cushions ex vivo. Here, we investigate the role of MBNL1 in endocardial cushion development and valvulogenesis in Mbnl1?E3/?E3 mice, which are null for MBNL1 protein. Methods: Collagen gel invasion assays, histology, immunohistochemistry, real-time RT-PCR, optical coherence tomography, and echocardiography were used to evaluate EMT and TGF? signaling in the endocardial cushions, and morphogenesis, ECM composition, and function of the heart valves. Results: As in chicken, the loss of MBNL1 promotes precocious TGF? signaling and EMT in the endocardial cushions. Surprisingly, this does not lead to the production of excess mesenchyme, but later valve morphogenesis is aberrant. Adult Mbnl1?E3/?E3 mice exhibit valve dysmorphia with elevated TGF? signaling, changes in ECM composition, and increased pigmentation. This is accompanied by a high incidence of regurgitation across both inflow and outflow valves. Mbnl1?E3/?E3 mice also have a high incidence of ostium secundum septal defects accompanied by atrial communication, but do not develop overt cardiomyopathy. Conclusions: Together, these data indicate that MBNL1 plays a conserved role in negatively regulating TGF? signaling, and is required for normal valve morphogenesis and homeostasis in vivo. Electronic supplementary material: The online version of this article (doi:10.1186/s12861-015-0087-4) contains supplementary material, which is available to authorized users.
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BMC+Dev+Biol 2015 ; 15 (ä): ä
