Novel Dual Reporter Mouse Model Provides Definitive Labeling and Identification of Smooth Muscle Cells-Brief Report.

Objective: encodes a myosin heavy chain protein that is specifically expressed in smooth muscle cells (SMCs) and is important for maintaining vascular wall stability. The goal of this study is to generate a dual reporter mouse line for definitive visualization of MYH11 SMCs in vivo. Approach and Results: We generated a knock-in mouse model by inserting reporter cassette into the gene locus. The nuclear (n) cassette is flanked by 2 sites followed by H2B-GFP (histone 2B fused green fluorescent protein). Upon Cre-mediated recombination, cassette is removed thereby permitting nucleus localized H2B-GFP expression. Expression of the nuclear localized lacZ or H2B-GFP is under control of the endogenous promoter. Nuclear lacZ was expressed specifically in SMCs at embryonic and adult stages. Following germline Cre-mediated deletion of nuclear lacZ, H2B-GFP was specifically expressed in the nuclei of SMCs. Comparison of nuclear lacZ expression with and mediated-H2B-GFP expression revealed heterogenous origins of SMCs from neural crest and second heart field in the great arteries and coronary vessels adjacent to aortic root.

Conclusions: The knock-in dual reporter mouse model offers an exceptional genetic tool to visualize and trace the origins of SMCs in mice.