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INDIVIDUAL RESEARCHER

Xiaochun Long , Ph.D
Assistant Professor
e-mail: longx@mail.amc.edu

Phone: 5182642539
Fax: 5182628101

Education

2003 - Ph.D from Tongji Medical College, Huazhong University of Science and Technology


Current Research

  Mature vascular smooth muscle cells (VSMC) express cell-restricted genes encoding ion channels, cyto-contractile and matrix proteins, and a growing number of non-coding RNAs that collectively maintain a quiescent contractile phenotype conducive for normal blood flow and blood pressure. A large body of work has documented that VSMC are endowed with remarkable plasticity through altered contractile phenotype to a so called synthetic state in response to various environment stimuli, a process we refer to as VSMC phenotypic adaptation. Synthetic VSMC are pro-inflammatory, matrix remodeling-prone, highly proliferative and migratory, and thus contribute to neointimal formation, which underlies the pathogenesis of such vascular diseases as atherosclerosis, restenosis, hypertension, vein graft failure, and transplant arteriopathy. My research interest is focused on how VSMC phenotypic adaptation is regulated. I am particularly interested in defining novel regulators of VSMC phenotypic adaptation, including important transcription factors, signal transducers and long non-coding RNAs.

 Three active ongoing projects are described as follows:

1.       Define Novel Role of MAPK14 in Vascular Smooth Muscle Differentiation
Serum response factor (SRF) and the Myocardin family of coactivators (e.g., MRTFA) have emerged as key inducers of the VSMC contractile phenotype. Although there has been much work on SRF-MRTFA-dependent gene expression in VSMC, a critical gap exists with respect to our understanding of signaling pathways that converge upon SRF-MRTFA to negatively control VSMC gene expression.  We found knock-down of MAPK14, a major isoform of p38MAPK in VSMC targeted by SB compound, stimulates contractile gene expression in multiple species of VSMC. Further, vascular injury models reveal total and phosphorylated MAPK14 are enriched in the neointima of the vessel wall where phenotypically altered VSMC reside. Mechanistically, we discovered that MAPK14 regulates MRTFA nucleo-cytoplasmic shuttling, a critical determinant of SRF-dependent VSMC contractile gene expression. In the future studies, we will elucidate the role of MAPK14 in VSMC phenotypic plasticity leading to vascular disease using inducible, VSMC-specific Mapk14 knockout mice. Using the Mrtfa-/-/Mapk14-/- double knockout mice, we will dissect the integrative role of MAPK14 and MRTFA in regulating VSMC differentiation in vivo.
2.       Molecular regulation and functionality characterization of novel long non-coding RNAs in VSMC phenotypic adaptation
Recently, the old concept of “junk DNA” has been undermined by the large number of papers released from ENCyclopedia Of DNA Elements (ENCODE) Consortium. The general conclusion reached from these papers is the human genome undergoes “pervasive transcription”, such that 80% of our code is functional. Another important discovery from ENCODE is the majority of transcribed sequences are non-coding RNAs which include short non-coding RNAs (such as microRNAs) and long non-coding RNAs (such as long intergenic non-coding RNA, lncRNAs). Thus far, more than 80,000 lncRNAs have been identified, a number far exceeding that of protein-coding genes, indicating a dominant role over the mammalian genome.  lncRNAs have been shown to function as important regulators in stem cell pluripotency, cellular differentiation, cell cycle progression and in human disease. Currently, there is a paucity of information about lncRNAs in vascular pathobiology.  In order to screen for novel regulators of VSMC phenotype, we performed several RNA-seq using different innovative VSMC culture systems, including TGFβ1 and Myocardin -induced human coronary artery SMC. Excitingly, we found a subset of novel lncRNAs turned out to be tightly regulated by both TGFβ1 and Myocardin. Expression profile studies demonstrated some of these targets are very restricted to VSMC. Further studies revealed the expression of these VSMC-specific novel lncRNAs is closely linked to VSMC adaptation. Thus, we hypothesize these lncRNAS are the potential novel regulators in controlling VSMC phenotype. In the future goal, we will define the functionality of these potential lncRNAs in VSMC phenotypic adaptation by utilizing the established in vitro or ex vivo VSMC culture systems and transgenic/knockout mouse models.
 
3.       Define the role of novel TGFβ1/MYOCD-regulated protein coding genes in VSMC phenotypic adaptation
The aforementioned RNA-seq data also uncovered a number of novel protein-coding genes (such as TSPAN2, MAMDC2)which are potentially important in VSMC phenotypic adaptation. One of our future goals is to define the role of these novel protein coding targets in different vascular disease models such as carotid artery ligation model, mouse abdominal aortic aneurysym (AAA) and vein graft models.


PubMed Publications

  1. Long X*, Bell RD* , Lin M*, Bergmann JH, Nanda V, Cowan SL, Zhou Q, Han Y, Spector DL, Zheng D, Miano JM. Identification and Initial Functional Characterization of a Human Vascular Cell-Enriched Long Noncoding RNA. Arterioscler Thromb Vasc Biol. 2014 Feb 27. * equal contribution


  2. Long X, Miano JM. Myocardin: new therapeutic agent in vascular disease? Arterioscler Thromb Vasc Biol. 2013, 33(10):2284-5.


  3. Shi G, Field DJ, Long X, Mickelsen D, Ko KA, Ture S, Korshunov VA, Miano JM, Morrell CN. Platelet factor 4 mediates vascular smooth muscle cell injury responses. Blood. 2013, 121(21):4417-27.


  4. Imamura M, Sugino Y, Long X, Slivano OJ, Nishikawa N, Yoshimura N, Miano JM. Myocardin and MicroRNA-1 modulate bladder activity through connexin 43 expression during post-natal development. J Cell Physiol. 2013, doi: 10.1002/jcp.24333.


  5. Long X, Cowan SL, Miano JM. MAPK14 is a Homeostatic Switch for the Vascular Smooth Muscle Cell Contractile Gene Program. Arterioscler Thromb Vasc Biol. 2013, 33(2):378- 86. (Cover Photograph) (Corresponding author)


  6. Kitchen CM, Cowan SL, Long X, Miano JM. Expression and promoter analysis of a highly restricted integrin alpha gene in vascular smooth muscle. Gene. 2013, 513(1): 82-9.


  7. Long X, Slivano OJ, Cowan SL, Georger MA, Lee TH, Miano JM. Smooth Muscle Calponin: An Unconventional CArG-Dependent Gene That Antagonizes Neointimal Formation. Arterioscler Thromb Vasc Biol. 2011, 31(10): 2172-80. (Cover Photograph)


  8. Long X, Miano JM. TGF?1 utilizes distinct pathways for the transcriptional activation of microRNA 143/145 in human coronary artery smooth muscle cells. J Biol Chem. 2011, 286(34):30119-29. (Co-corresponding author)


  9. Benson CC, Zhou Q, Long X, Miano JM. Identifying Functional Single Nucleotide Polymorphisms in the Human CArGome. Physiol Genomics. 2011, 43(18): 1038-48.


  10. Streb JW, Long X, Lee TH, Sun Q, Kitchen CM, Georger MA, Slivano OJ, Blaner WS, Carr DW, Gelman IH, Miano JM. Retinoid-induced expression and activity of an immediate early tumor suppressor gene in vascular smooth muscle cells. PLoS One. 2011, 6(4):e18538


  11. Xie WB, Li Z, Miano JM, Long X, Chen SY. Smad3-mediated myocardin silencing: a novel mechanism governing the initiation of smooth muscle differentiation. J Biol Chem. 2011, 286(17):15050-7.


  12. Imamura M, Long X, Nanda V, Miano JM. Expression and Functional Activity of Four Myocardin Isoforms. Gene. 2010, 464(1-2):1-10.


  13. Long X, Tharp DL, Georger MA, Slivano OJ, Lee MY, Wamhoff BR, Bowles DK, Miano JM. The smooth muscle cell-restricted KCNMB1 ion channel subunit is a direct transcriptional target of serum response factor and myocardin. J Biol Chem. 2009 284(48):33671-82.


  14. Sun Q, Taurin S, Sethakorn N, Long X, Imamura M, Wang DZ, Zimmer WE, Dulin NO, Miano JM. Myocardin-dependent activation of the CArG box-rich smooth muscle gamma-actin gene: preferential utilization of a single CArG element through functional association with the NKX3.1 homeodomain protein. J Biol Chem. 2009, 284(47):32582-90.


  15. Bell RD, Deane R, Chow N, Long X, Sagare A, Singh I, Streb JW, Guo H, Rubio A, Van Nostrand W, Miano JM, Zlokovic BV. SRF and myocardin regulate LRP-mediated amyloid-beta clearance in brain vascular cells. Nat Cell Biol. 2009, 11(2):143-53.


  16. Long X, Bell RD, Gerthoffer WT, Zlokovic BV, Miano JM. Myocardin Is Sufficient for a Smooth Muscle-Like Contractile Phenotype. Arterioscler Thromb Vasc Biol. 2008, 28(8):1505-10.


  17. Long X*, Davis JL*, Georger MA, Scott IC, Rich A, Miano JM. Expression and comparative genomics of two serum response factor genes in zebrafish. Int J Dev Biol. 2008, 52(4):389-96. * equal contribution


  18. Long X*, Creemers E.E*. Wang D.Z., Olson E.N., and Miano. J.M. Myocardin is a bifunctional switch for smooth versus skeletal muscle differentiation. Proc Natl Acad Sci U S A. 2007, 104(42):16570-5 * equal contribution


  19. Long X, Miano JM. Remote control of gene expression. J. Biol. Chem. 2007, 282(22): 15941-15945.


  20. Miano, J.M., Long X, Fujiwara, K. Serum response factor: master regulator of the actin cytoskeleton and contractile apparatus. Am J Physiol Cell Physiol. 2007, 292: C70-C81.


  21. Rensen, S.S.M., Niessen, P.M.G., Long, X, Doevendans, P.A., Miano, J.M., van Eys, G.J.J.M. Contribution of serum response factor and myocardin to transcriptional regulation of smoothelins. Cardiovasc.Res. 2006, 70:136-145.


  22. Sun Q, Chen G, Streb JW, Long X, Yang Y, Stoeckert CJ Jr, Miano JM. Defining the mammalian CArGome. Genome Res. 2006, 16:197-207.