Arteriosclerotic calcification is a complication of diabetes, dyslipidemia, and aging that increases risk of stroke, heart failure, and foot amputation. Arteriosclerosis impairs the elasticity of conduit arteries necessary for smooth distal tissue perfusion and adaptation to physiological demands. Our goal is to develop novel therapeutic strategies to mitigate arteriosclerosis -- translated from a fundamental understanding of pathobiology via preclinical disease models. In the past funding period, we showed that osteogenic Wnt signals are important in the arteriosclerosis of diabetes and dyslipidemia. LRP6, a Wnt co-receptor known for capacity to support canonical actions, was identified to limit noncanonical Wnt signaling in vascular smooth muscle (VSM) that drives calcification. Loss of VSM LRP6 increases arterial calcification & stiffness by enhancing VSM osteogenic differentiation and increasing protein arginine methylation. Mass spectrometry identified that one methylated protein, G3BP1, supports noncanonical Wnt pathways by activating NFATc4 in concert with Ddx58. Ddx58 is cytosolic receptor for atypical RNAs and part of the mitochondrial antiviral signaling protein (MAVS) system. Recently, gain-of-function mutations in Ddx58 have been shown to cause Singleton Merten Syndrome 2 (SGMRT2) a disorder characterized by precocious aortic, aortic valve, and coronary calcification. In preliminary data, we show that: (a) Ddx58 promotes G3BP1 methylation and signaling; (b) Ddx58- and MAVS-deficient VSM exhibit reduced noncanonical Wnt/NFAT signaling, osteogenic differentiation and calcification; and (c) SGMRT2 variants are gain-of-function in our assays. We?ve also shown that MAVS-/-;LDLR-/- mice exhibit less aortic calcification when fed arteriosclerotic diets. In this renewal our aims are:
Aim1 : ?To complete our ongoing characterization of MAVS-/-;LDLR-/- mice, elucidating the mechanisms whereby the MAVS relay conveys arteriosclerotic Wnt signals in vascular smooth muscle.? We study the impact of MAVS deficiency on arterial calcification, stiffening, atheroma formation and vascular activation of NFAT signals. We focus upon VSM cell-autonomous contributions, since our data show that Wnt- regulated NFATc4 nuclear localization and osteogenic mineralization require MAVS. We also study how MAVS deficiency impacts arterial remodeling in the angiotensin-II infusion model of aortic aneurysm formation.
Aim2 : ?To generate and characterize mice possessing a gain-of-function allele for the MAVS activator Ddx58 as a preclinical model of the arterial calcification of Singleton Merten Syndrome Type 2.? We implement CRISPR/Cas9 with a mutated ssDNA homology directed repair template to generate Ddx58(SGMRT2/+) mice (collaboration with Drs. R. Hammer and ZJ Chen). We first characterize whether this SGMRT2 Ddx58 allele promotes arteriosclerotic calcification in vivo, and VSM mineralization and NFAT signaling in vitro. In outlying years we then initiate studies into the impact of Ddx58 deficiency on arteriosclerosis, and the role of Wnt16 ? a potential therapeutic target highly expressed in VSM ? in the paracrine regulation of Ddx58/MAVS relays.
Arterial hardening with diabetes and aging increases the risk for heart attacks, heart failure, stroke, dementia, and foot amputation. This occurs in part via inflammation that induces bone-like calcification in large arteries and heart valves. We have identified that the proteins MAVS and Ddx58 might work together to control hardening of the arteries. We test whether regulation of these proteins can reduce arterial hardening and improve cardiovascular health. Genetic studies from humans indicate that Ddx58 is very important. We develop a model of a rare human cardiovascular disease to study Ddx58 actions and identify new approaches to prevent artery and valve calcification.
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