title: Dual effects of the homeobox transcription factor Csx/Nkx2-5 on cardiomyocytes.
abstract: A homeobox-containing transcription factor Csx/Nkx2-5 is an important regulator of cardiac development. Many different human CSX/NKX2-5 mutations have been reported to cause congenital heart disease. We here examined the effects of three representative CSX/NKX2-5 mutations on cardiomyocyte differentiation and death with the use of the P19CL6 cardiomyogenic cell lines. Stable overexpression of wild-type CSX/NKX2-5 enhanced expression of cardiac-specific genes such as MEF2C and MLC2v, the promoter activity of the atrial natriuretic peptide gene, and the terminal differentiation of P19CL6 into cardiomyocytes, while all CSX/NKX2-5 mutants attenuated them by different degrees. When exposed to H(2)O(2) or cultured without change of the medium, many differentiated P19CL6 cells overexpressing the mutants, especially the mutant which lacks the carboxyl terminal region just after the homeodomain, were dead, while most of the cells overexpressing wild-type CSX/NKX2-5 survived. Overexpression of the carboxyl terminus-deleted mutant down-regulated expression of an anti-apoptotic protein Bcl-x(L) and up-regulated that of a pro-apoptotic protein CAS, while in the cells overexpressing wild-type CSX/NKX2-5, expression of a pro-apoptotic protein RIP was reduced. Furthermore, overexpression of wild-type CSX/NKX2-5 decreased the number of H(2)O(2)-induced TUNEL-positive cultured cardiomyocytes of neonatal rats, whereas overexpression of the mutants enhanced it. These results suggest that Csx/Nkx2-5 not only regulates expression of cardiac-specific genes but protects cardiomyocytes from stresses and that cell death may be another cause for the cardiac defects induced by human CSX/NKX2-5 mutations.
authors.affiliation: Department of Cardiovascular Medicine, University of Tokyo Graduate School of Medicine, Tokyo 113-8655, Japan.
authors.forename: Koshiro
authors.initials: K
authors.lastname: Monzen
authors.forename: Weidong
authors.initials: W
authors.lastname: Zhu
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kasai
authors.forename: Yukio
authors.initials: Y
authors.lastname: Hiroi
authors.forename: Toru
authors.initials: T
authors.lastname: Hosoda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Akazawa
authors.forename: Yunzeng
authors.initials: Y
authors.lastname: Zou
authors.forename: Doubun
authors.initials: D
authors.lastname: Hayashi
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Ryozo
authors.initials: R
authors.lastname: Nagai
authors.forename: Issei
authors.initials: I
authors.lastname: Komuro
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D009206:Myocardium / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
chemical_list: D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; D014157:Transcription Factors