CARMN Is an Evolutionarily Conserved Smooth Muscle Cell–Specific LncRNA That Maintains Contractile Phenotype by Binding Myocardin

• Published in: Circulation (New York, N.Y.) Vol. 144; no. 23; pp. 1856 - 1875
• Main Authors: Dong, Kunzhe, Shen, Jian, He, Xiangqin, Hu, Guoqing, Wang, Liang, Osman, Islam, Bunting, Kristopher M., Dixon-Melvin, Rachael, Zheng, Zeqi, Xin, Hongbo, Xiang, Meixiang, Vazdarjanova, Almira, Fulton, David J.R., Zhou, Jiliang
• Format: Journal Article
• Language: English
• Published: United States Lippincott Williams & Wilkins 07-12-2021
• Subjects: Animals; Humans; Mice; Muscle Contraction; Muscle, Smooth - metabolism; Muscle, Smooth, Vascular - metabolism; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Rats; RNA, Long Noncoding - genetics; RNA, Long Noncoding - metabolism; Trans-Activators - genetics; Trans-Activators - metabolism; RNA, long noncoding; myocytes, smooth muscle; vascular diseases
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/CIRCULATIONAHA.121.055949

Vascular homeostasis is maintained by the differentiated phenotype of vascular smooth muscle cells (VSMCs). The landscape of protein coding genes comprising the transcriptome of differentiated VSMCs has been intensively investigated but many gaps remain including the emerging roles of noncoding genes.
We reanalyzed large-scale, publicly available bulk and single-cell RNA sequencing datasets from multiple tissues and cell types to identify VSMC-enriched long noncoding RNAs. The in vivo expression pattern of a novel smooth muscle cell (SMC)-expressed long noncoding RNA,
(cardiac mesoderm enhancer-associated noncoding RNA), was investigated using a novel
green fluorescent protein knock-in reporter mouse model. Bioinformatics and quantitative real-time polymerase chain reaction analysis were used to assess
expression changes during VSMC phenotypic modulation in human and murine vascular disease models. In vitro, functional assays were performed by knocking down
with antisense oligonucleotides and overexpressing
by adenovirus in human coronary artery SMCs. Carotid artery injury was performed in SMC-specific
knockout mice to assess neointima formation and the therapeutic potential of reversing
loss was tested in a rat carotid artery balloon injury model. The molecular mechanisms underlying
function were investigated using RNA pull-down, RNA immunoprecipitation, and luciferase reporter assays.
We identified
, which was initially annotated as the host gene of the
cluster and recently reported to play a role in cardiac differentiation, as a highly abundant and conserved, SMC-specific long noncoding RNA. Analysis of the
GFP knock-in mouse model confirmed that
is transiently expressed in embryonic cardiomyocytes and thereafter becomes restricted to SMCs. We also found that
is transcribed independently of
.
expression is dramatically decreased by vascular disease in humans and murine models and regulates the contractile phenotype of VSMCs in vitro. In vivo, SMC-specific deletion of
significantly exacerbated, whereas overexpression of
markedly attenuated, injury-induced neointima formation in mouse and rat, respectively. Mechanistically, we found that
physically binds to the key transcriptional cofactor myocardin, facilitating its activity and thereby maintaining the contractile phenotype of VSMCs.
is an evolutionarily conserved SMC-specific long noncoding RNA with a previously unappreciated role in maintaining the contractile phenotype of VSMCs and is the first noncoding RNA discovered to interact with myocardin.