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J Clin Invest. 2019 Feb 1;129(2):659-675. doi: 10.1172/JCI123547. Epub 2019 Jan 7.

Lineage-specific events underlie aortic root aneurysm pathogenesis in Loeys-Dietz syndrome.

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McKusick-Nathans Institute of Genetic Medicine.
Department of Surgery.
Division of Cardiology, and.
McKusick-Nathans Institute of Genetic Medicine, Human Genetics Program, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA.
Division of Pediatric Cardiology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Howard Hughes Medical Institute, Bethesda, Maryland, USA.


The aortic root is the predominant site for development of aneurysm caused by heterozygous loss-of-function mutations in positive effectors of the transforming growth factor-β (TGF-β) pathway. Using a mouse model of Loeys-Dietz syndrome (LDS) that carries a heterozygous kinase-inactivating mutation in TGF-β receptor I, we found that the effects of this mutation depend on the lineage of origin of vascular smooth muscle cells (VSMCs). Secondary heart field-derived (SHF-derived), but not neighboring cardiac neural crest-derived (CNC-derived), VSMCs showed impaired Smad2/3 activation in response to TGF-β, increased expression of angiotensin II (AngII) type 1 receptor (Agtr1a), enhanced responsiveness to AngII, and higher expression of TGF-β ligands. The preserved TGF-β signaling potential in CNC-derived VSMCs associated, in vivo, with increased Smad2/3 phosphorylation. CNC-, but not SHF-specific, deletion of Smad2 preserved aortic wall architecture and reduced aortic dilation in this mouse model of LDS. Taken together, these data suggest that aortic root aneurysm predisposition in this LDS mouse model depends both on defective Smad signaling in SHF-derived VSMCs and excessive Smad signaling in CNC-derived VSMCs. This work highlights the importance of considering the regional microenvironment and specifically lineage-dependent variation in the vulnerability to mutations in the development and testing of pathogenic models for aortic aneurysm.


Monogenic diseases; Mouse models; Signal transduction; Vascular Biology

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