Muscleblind-like 1 is required for normal heart valve development in vivo

BMC Developmental Biology

Andrea N. Ladd⁴  Maurice S. Swanson⁵  Michael W. Jenkins¹  Anuradha Guggilam⁴  Samantha J. Stillwagon³  Ryan J. Coram² 

[1] Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland 44106, OH, USA;Present Address: Ohio University Heritage College of Osteopathic Medicine, Athens 45701, OH, USA;Present Address: Department of Obstetrics and Gynecology, Women’s Health Institute, Cleveland Clinic, Cleveland 44195, OH, USA;Department of Cellular & Molecular Medicine, Lerner Research Institute, 9500 Euclid Ave. NC10, Cleveland Clinic, Cleveland 44195, OH, USA;Department of Molecular Genetics & Microbiology, College of Medicine, Center for NeuroGenetics and the Genetics Institute, University of Florida, Gainesville 32610, FL, USA

关键词: Mouse;    Heart valves;    Endocardial cushions;    Epithelial-mesenchymal transition;    Transforming growth factor β;    Muscleblind-like 1;   

Others  :  1231010
DOI  :  10.1186/s12861-015-0087-4

 received in 2015-07-27, accepted in 2015-10-09,  发布年份 2015

【 摘 要 】

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 β (TGFβ) 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 TGFβ 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/∆E3mice, 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 TGFβ 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 TGFβ 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 TGFβ 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 TGFβ signaling, and is required for normal valve morphogenesis and homeostasis in vivo.

【 授权许可】

   
2015 Coram et al.

【 图 表 】

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