title: Downregulation of Rho associated coiled-coil forming protein kinase 1 in the process of delayed myocardialization of cardiac proximal outflow tract septum in connexin 43 knockout mice embryo.
abstract: BACKGROUND
  The connexin43 knockout (Cx43 KO) mouse dies at birth with an enlarged conotruncal region, which leads to the obstruction of the right outflow tract (OFT). Since myocardialization of the proximal OFT septum is one of the key events during heart development, we investigated the process in the Cx43 KO embryo hearts. Rho associated coiled-coil forming protein kinase 1 (ROCK1), is a recently found key molecule to regulate the myocardialization of OFT, but its spatiotemporal expression pattern during myocardialization remains unknown. The objective of this study was to investigate the differentially expressed pattern of ROCK1 between Cx43 KO and wild type embryo hearts, and its relationship with the delayed myocardialization in Cx43 KO embryo hearts.
  
  
  METHODS
  Using immunohistochemistry, the processes of myocardiolization were investigated both in Cx43 KO and wild type embryo hearts. The differentially expressed pattern of ROCK1 between Cx43 KO and wildtype embryo hearts was evaluated both at the mRNA and protein level by real-time RT-PCR and immunohistochemistry.
  
  
  RESULTS
  The expression of α-sarcomeric actin (α-SCA) in the proximal OFT septum of Cx43 KO embryos was delayed. Meanwhile, it was shown that the downregulation of ROCK1 coincided with delayed myocardialization. The expression of ROCK1 protein was mainly limited to the proximal outflow tract septum from embryo day (E) E11.5 to E15.5. Its expression pattern was similar with that of α-SCA. Real-time RT-PCR found that the expression level of Rock-1 mRNA began at a low level on E11.5 and reached peak at E13.5 and E14.5.
  
  
  CONCLUSIONS
  ROCK1 may have an important role in the process of myocardialization of the proximal OFT septum. Downregulation of ROCK1 is likely to contribute to the aberrant myocardialization in Cx43 KO embryo hearts.
authors.affiliation: Pediatric Heart Center, Children's Hospital of Fudan University, Shanghai 201102, China.
authors.forename: Chun-hua
authors.initials: CH
authors.lastname: Qi
authors.forename: Xiao-qing
authors.initials: XQ
authors.lastname: Zhao
authors.forename: Duan
authors.initials: D
authors.lastname: Ma
authors.forename: Xiao-jing
authors.initials: XJ
authors.lastname: Ma
authors.forename: Guo-min
authors.initials: GM
authors.lastname: Zhou
authors.forename: Guo-ying
authors.initials: GY
authors.lastname: Huang
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D006321:Heart / Q000196:embryology / Q000503:physiopathology; D006346:Heart Septum; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D060888:Real-Time Polymerase Chain Reaction; D054460:rho-Associated Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D018031:Connexin 43; C544013:alpha-smooth muscle actin, mouse; C515854:Rock1 protein, mouse; D054460:rho-Associated Kinases