title: The role of Bcl6 in mature cardiac myocytes.
abstract: OBJECTIVE
  The Bcl6 gene encodes a sequence-specific transcriptional repressor and is ubiquitously expressed in adult murine tissues including heart muscle. The objective of this study was to examine the role of Bcl6 in cardiac myocytes.
  
  
  METHODS
  We developed Bcl6-deficient (Bcl6-/-) mice and histologically examined hearts from these mice.
  
  
  RESULTS
  Massive myocarditis with eosinophilic infiltration occurred in Bcl6-/- mice after 4-6 weeks of age. Since expression of the Bcl6 gene was induced in normal cardiac myocytes after 2 weeks of age and thereafter detected through adulthood, loss of Bcl6 in mature cardiac myocytes may be related to the induction of eosinophilic myocarditis. To examine the effects of eosinophils from Bcl6-/- mice on normal hearts, bone marrow cells from Bcl6-/- mice were adoptively transferred into sublethally irradiated RAG1-deficient mice. Although massive eosinophilic infiltration was detected in conjunctivas and spleens from the chimeric mice, myocarditis was never observed. Electron microscopic analysis of cardiac myocytes from Bcl6-/- mice revealed a spectrum of degenerative changes prior to eosinophilic infiltration.
  
  
  CONCLUSIONS
  Bcl6 maynot be essential for the maturation of cardiac myocytes but may play a role in protecting mature cardiac myocytes from eosinophilic inflammation.
authors.affiliation: Department of Developmental Genetics, Chiba University Graduate School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yoshida
authors.forename: T
authors.initials: T
authors.lastname: Fukuda
authors.forename: M
authors.initials: M
authors.lastname: Hatano
authors.forename: H
authors.initials: H
authors.lastname: Koseki
authors.forename: S
authors.initials: S
authors.lastname: Okabe
authors.forename: K
authors.initials: K
authors.lastname: Ishibashi
authors.forename: S
authors.initials: S
authors.lastname: Kojima
authors.forename: M
authors.initials: M
authors.lastname: Arima
authors.forename: I
authors.initials: I
authors.lastname: Komuro
authors.forename: G
authors.initials: G
authors.lastname: Ishii
authors.forename: T
authors.initials: T
authors.lastname: Miki
authors.forename: S
authors.initials: S
authors.lastname: Hirosawa
authors.forename: N
authors.initials: N
authors.lastname: Miyasaka
authors.forename: M
authors.initials: M
authors.lastname: Taniguchi
authors.forename: T
authors.initials: T
authors.lastname: Ochiai
authors.forename: K
authors.initials: K
authors.lastname: Isono
authors.forename: T
authors.initials: T
authors.lastname: Tokuhisa
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D016026:Bone Marrow Transplantation; D004268:DNA-Binding Proteins / Q000235:genetics*; D004802:Eosinophilia / Q000378:metabolism* / Q000473:pathology; D017353:Gene Deletion; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D008854:Microscopy, Electron; D009205:Myocarditis / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051560:Proto-Oncogene Proteins c-bcl-6; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D051560:Proto-Oncogene Proteins c-bcl-6; D014157:Transcription Factors