Leiomodin 1, a New Serum Response Factor-dependent Target Gene Expressed Preferentially in Differentiated Smooth Muscle Cells

Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 12/2011; 287(4):2459-67. DOI: 10.1074/jbc.M111.302224
Source: PubMed

ABSTRACT Smooth muscle cell (SMC) differentiation is defined largely by a number of cell-restricted genes governed directly by the serum response factor (SRF)/myocardin (MYOCD) transcriptional switch. Here, we describe a new SRF/MYOCD-dependent, SMC-restricted gene known as Leiomodin 1 (Lmod1). Conventional and quantitative RT-PCRs indicate that Lmod1 mRNA expression is enriched in SMC-containing tissues of the mouse, whereas its two paralogs, Lmod2 and Lmod3, exhibit abundant expression in skeletal and cardiac muscle with very low levels in SMC-containing tissues. Western blotting and immunostaining of various adult and embryonic mouse tissues further confirm SMC-specific expression of the LMOD1 protein. Comparative genomic analysis of the human LMOD1 and LMOD2 genes with their respective mouse and rat orthologs shows high conservation between the three exons and several noncoding sequences, including the immediate 5' promoter region. Two conserved CArG boxes are present in both the LMOD1 and LMOD2 promoter regions, although LMOD1 displays much higher promoter activity and is more responsive to SRF/MYOCD stimulation. Gel shift assays demonstrate clear binding between SRF and the two CArG boxes in human LMOD1. Although the CArG boxes in LMOD1 and LMOD2 are similar, only LMOD1 displays SRF or MYOCD-dependent activation. Transgenic mouse studies reveal wild type LMOD1 promoter activity in cardiac and vascular SMC. Such activity is abolished upon mutation of both CArG boxes. Collectively, these data demonstrate that Lmod1 is a new SMC-restricted SRF/MYOCD target gene.

Download full-text


Available from: Joseph Miano, Feb 03, 2015
10 Reads
  • Source
    • "Our results showed that this gene was up-regulated in HUAECs compared to HUVECs. We also observed an increased level of expression of LMOD1 (Leiomodin 1) in HUAECs as compared to HUVECs, which correlated with the protein expression in mouse aorta [34]. MMP9 (Matrix Metalloproteases 9), which degrades the extracellular matrix to allow for endothelial sprouting, is essential for angiogenesis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The vascular system is adapted to specific functions in different tissues and organs. Vascular endothelial cells are important elements of this adaptation, leading to the concept of 'specialized endothelial cells'. The phenotype of these cells is highly dependent on their specific microenvironment and when isolated and cultured, they lose their specific features after few passages, making models using such cells poorly predictive and irreproducible. We propose a new source of specialized endothelial cells based on cord blood circulating endothelial progenitors (EPCs). As prototype examples, we evaluated the capacity of EPCs to acquire properties characteristic of cerebral microvascular endothelial cells (blood-brain barrier (BBB)) or of arterial endothelial cells, in specific inducing culture conditions. First, we demonstrated that EPC-derived endothelial cells (EPDCs) co-cultured with astrocytes acquired several BBB phenotypic characteristics, such as restricted paracellular diffusion of hydrophilic solutes and the expression of tight junction proteins. Second, we observed that culture of the same EPDCs in a high concentration of VEGF resulted, through activation of Notch signaling, in an increase of expression of most arterial endothelial markers. We have thus demonstrated that in vitro culture of early passage human cord blood EPDCs under specific conditions can induce phenotypic changes towards BBB or arterial phenotypes, indicating that these EPDCs maintain enough plasticity to acquire characteristics of a variety of specialized phenotypes. We propose that this property of EPDCs might be exploited for producing specialized endothelial cells in culture to be used for drug testing and predictive in vitro assays.
    PLoS ONE 01/2014; 9(1):e84179. DOI:10.1371/journal.pone.0084179 · 3.23 Impact Factor
  • Source
    • "Other well-characterized markers of mature VSMC include actin cross-linking protein transgelin (SM22α), and the calcium binding protein and inhibitor of SM-MHC intrinsic ATPase activity, calponin. Leiomodin-1, a gene target of SRF/myocardin dependent transcription, was recently described as a novel marker of contractile VSMC (Nanda and Miano, 2012). Regulation of the actin cytoskeleton and contractile machinery of VSMC by SRF has previously been reviewed (Miano et al., 2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Notch signaling in the cardiovascular system is important during embryonic development, vascular repair of injury, and vascular pathology in humans. The vascular smooth muscle cell (VSMC) expresses multiple Notch receptors throughout its life cycle, and responds to Notch ligands as a regulatory mechanism of differentiation, recruitment to growing vessels, and maturation. The goal of this review is to provide an overview of the current understanding of the molecular basis for Notch regulation of VSMC phenotype. Further, we will explore Notch interaction with other signaling pathways important in VSMC.
    Frontiers in Physiology 04/2012; 3:81. DOI:10.3389/fphys.2012.00081 · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tropomodulins are a family of four proteins (Tmods 1-4) that cap the pointed ends of actin filaments in actin cytoskeletal structures in a developmentally regulated and tissue-specific manner. Unique among capping proteins, Tmods also bind tropomyosins (TMs), which greatly enhance the actin filament pointed-end capping activity of Tmods. Tmods are defined by a TM-regulated/Pointed-End Actin Capping (TM-Cap) domain in their unstructured N-terminal portion, followed by a compact, folded Leucine-Rich Repeat/Pointed-End Actin Capping (LRR-Cap) domain. By inhibiting actin monomer association and dissociation from pointed ends, Tmods regulate actin dynamics and turnover, stabilizing actin filament lengths and cytoskeletal architecture. In this review, we summarize the genes, structural features, molecular and biochemical properties, actin regulatory mechanisms, expression patterns, and cell and tissue functions of Tmods. By understanding Tmods' functions in the context of their molecular structure, actin regulation, binding partners, and related variants (leiomodins 1-3), we can draw broad conclusions that can explain the diverse morphological and functional phenotypes that arise from Tmod perturbation experiments in vitro and in vivo. Tmod-based stabilization and organization of intracellular actin filament networks provide key insights into how the emergent properties of the actin cytoskeleton drive tissue morphogenesis and physiology.
    Cytoskeleton 06/2012; 69(6):337-70. DOI:10.1002/cm.21031 · 3.12 Impact Factor
Show more