| First Author | Coram RJ | Year | 2015 |
| Journal | BMC Dev Biol | Volume | 15 |
| Pages | 36 | PubMed ID | 26472242 |
| Mgi Jnum | J:239862 | Mgi Id | MGI:5881881 |
| Doi | 10.1186/s12861-015-0087-4 | Citation | Coram RJ, et al. (2015) Muscleblind-like 1 is required for normal heart valve development in vivo. BMC Dev Biol 15:36 |
| abstractText | 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 beta (TGFbeta) 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 TGFbeta 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 TGFbeta 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 TGFbeta 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 TGFbeta 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 TGFbeta signaling, and is required for normal valve morphogenesis and homeostasis in vivo. |
