title: Altered expression of retinoblastoma 1 in Hirschsprung's disease.
abstract: OBJECTIVE
  The retinoblastoma 1 (RB1) tumor suppressor is a critical regulator of cell cycle progression and development, and has been widely documented to be inactivated in human cancer. A recent study using RB1 knockout mice suggested a new role for RB1 in the normal regulation of the enteric nervous system (ENS), because of knockout mice showing ENS abnormalities and severe intestinal dysmotility. The aim of our study was to investigate the expression of RB1 in the normal human colon and in Hirschsprung's disease (HD).
  
  
  METHODS
  HD tissue specimens (n=10) were collected at the time of pull-through surgery, while colonic control samples were obtained at the time of colostomy closure in patients with imperforate anus (n=10). Immunolabeling of RB1 was visualized using confocal microscopy to assess protein distribution, while western blot analysis was undertaken to quantify RB1 protein expression.
  
  
  RESULTS
  Immunohistochemistry revealed RB1 co-localized with platelet derived growth factor receptor alpha-positive (PDGFRα+) cells, nitrergic neurons and glia in controls and the ganglionic region of HD, with a marked reduction in the aganglionic HD specimens. Western blotting revealed a marked decrease in RB1 protein expression in the aganglionic region of HD colon compared to ganglionic and normal controls.
  
  
  CONCLUSIONS
  We provide evidence of the presence of RB1 expression in the human colon in HD. As RB1 is known to colocalize with nitrergic neurons, the decreased expression of RB1 in the aganglionic bowel is most likely a secondary phenomenon because of the deficient nitrergic innervation in HD.
authors: National Children's Research Centre, Our Lady's Children's Hospital Crumlin, Dublin, Ireland.
authors: Anne Marie
authors: AM
authors: O'Donnell
authors: National Children's Research Centre, Our Lady's Children's Hospital Crumlin, Dublin, Ireland.
authors: David
authors: D
authors: Coyle
authors: National Children's Research Centre, Our Lady's Children's Hospital Crumlin, Dublin, Ireland. Electronic address: prem.puri@ncrc.ie.
authors: Prem
authors: P
authors: Puri
mesh_terms: D015153:Blotting, Western; D003106:Colon / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006627:Hirschsprung Disease / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D008297:Male; D018613:Microscopy, Confocal; D056286:Retinoblastoma Binding Proteins / Q000096:biosynthesis*; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis*
chemical_list: C000606393:RB1 protein, human; D056286:Retinoblastoma Binding Proteins; D044767:Ubiquitin-Protein Ligases
keywords: Colonic aganglionosis; Enteric nervous; Hirschsprung's disease; Retinoblastoma 1