title: Modulation of angiotensin II-mediated cardiac remodeling by the MEF2A target gene Xirp2.
abstract: BACKGROUND
  The vasoactive peptide angiotensin II (Ang II) is a potent cardiotoxic hormone whose actions have been well studied, yet questions remain pertaining to the downstream factors that mediate its effects in cardiomyocytes.
  
  
  OBJECTIVE
  The in vivo role of the myocyte enhancer factor (MEF)2A target gene Xirp2 in Ang II-mediated cardiac remodeling was investigated.
  
  
  RESULTS
  Here we demonstrate that the MEF2A target gene Xirp2 (also known as cardiomyopathy associated gene 3 [CMYA3]) is an important effector of the Ang II signaling pathway in the heart. Xirp2 belongs to the evolutionarily conserved, muscle-specific, actin-binding Xin gene family and is significantly induced in the heart in response to systemic administration of Ang II. Initially, we characterized the Xirp2 promoter and demonstrate that Ang II activates Xirp2 expression by stimulating MEF2A transcriptional activity. To further characterize the role of Xirp2 downstream of Ang II signaling we generated mice harboring a hypomorphic allele of the Xirp2 gene that resulted in a marked reduction in its expression in the heart. In the absence of Ang II, adult Xirp2 hypomorphic mice displayed cardiac hypertrophy and increased beta myosin heavy chain expression. Strikingly, Xirp2 hypomorphic mice chronically infused with Ang II exhibited altered pathological cardiac remodeling including an attenuated hypertrophic response, as well as diminished fibrosis and apoptosis.
  
  
  CONCLUSIONS
  These findings reveal a novel MEF2A-Xirp2 pathway that functions downstream of Ang II signaling to modulate its pathological effects in the heart.
authors.affiliation: Department of Biology, Boston University, 24 Cummington St, Boston, MA 02215, USA.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: McCalmon
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Desjardins
authors.forename: Saad
authors.initials: S
authors.lastname: Ahmad
authors.forename: Katharine S
authors.initials: KS
authors.lastname: Davidoff
authors.forename: Christine M
authors.initials: CM
authors.lastname: Snyder
authors.forename: Kaori
authors.initials: K
authors.lastname: Sato
authors.forename: Koji
authors.initials: K
authors.lastname: Ohashi
authors.forename: Ondra M
authors.initials: OM
authors.lastname: Kielbasa
authors.forename: Matthen
authors.initials: M
authors.lastname: Mathew
authors.forename: Elizabeth P
authors.initials: EP
authors.lastname: Ewen
authors.forename: Kenneth
authors.initials: K
authors.lastname: Walsh
authors.forename: Haralambos
authors.initials: H
authors.lastname: Gavras
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Naya
mesh_terms: D000804:Angiotensin II / Q000008:administration & dosage; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D006332:Cardiomegaly / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005355:Fibrosis; D005786:Gene Expression Regulation; D015918:Infusion Pumps, Implantable; D055104:Infusions, Subcutaneous; D060588:LIM Domain Proteins; D064326:MEF2 Transcription Factors; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D015533:Transcriptional Activation; D024723:Ventricular Myosins / Q000378:metabolism; D020257:Ventricular Remodeling / Q000235:genetics
chemical_list: D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D060588:LIM Domain Proteins; D064326:MEF2 Transcription Factors; C578036:Mef2a protein, mouse; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; C500305:XIRP2 protein, mouse; D000804:Angiotensin II; D024723:Ventricular Myosins; D018995:Myosin Heavy Chains