title: Functional characterization of a novel mutation in NKX2-5 associated with congenital heart disease and adult-onset cardiomyopathy.
abstract: BACKGROUND
  The transcription factor NKX2-5 is crucial for heart development, and mutations in this gene have been implicated in diverse congenital heart diseases and conduction defects in mouse models and humans. Whether NKX2-5 mutations have a role in adult-onset heart disease is unknown.
  
  
  RESULTS
  Mutation screening was performed in 220 probands with adult-onset dilated cardiomyopathy. Six NKX2-5 coding sequence variants were identified, including 3 nonsynonymous variants. A novel heterozygous mutation, I184M, located within the NKX2-5 homeodomain, was identified in 1 family. A subset of family members had congenital heart disease, but there was an unexpectedly high prevalence of dilated cardiomyopathy. Functional analysis of I184M in vitro demonstrated a striking increase in protein expression when transfected into COS-7 cells or HL-1 cardiomyocytes because of reduced degradation by the Ubiquitin-proteasome system. In functional assays, DNA-binding activity of I184M was reduced, resulting in impaired activation of target genes despite increased expression levels of mutant protein.
  
  
  CONCLUSIONS
  Certain NKX2-5 homeodomain mutations show abnormal protein degradation via the Ubiquitin-proteasome system and partially impaired transcriptional activity. We propose that this class of mutation can impair heart development and mature heart function and contribute to NKX2-5-related cardiomyopathies with graded severity.
authors: Developmental and Stem Cell Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia. mauro.dacosta@monash.edu
authors: Mauro W
authors: MW
authors: Costa
authors: Guanglan
authors: G
authors: Guo
authors: Orit
authors: O
authors: Wolstein
authors: Molly
authors: M
authors: Vale
authors: Maria L
authors: ML
authors: Castro
authors: Libin
authors: L
authors: Wang
authors: Robyn
authors: R
authors: Otway
authors: Peter
authors: P
authors: Riek
authors: Natalie
authors: N
authors: Cochrane
authors: Milena
authors: M
authors: Furtado
authors: Christopher
authors: C
authors: Semsarian
authors: Robert G
authors: RG
authors: Weintraub
authors: Thomas
authors: T
authors: Yeoh
authors: Christopher
authors: C
authors: Hayward
authors: Anne
authors: A
authors: Keogh
authors: Peter
authors: P
authors: Macdonald
authors: Michael
authors: M
authors: Feneley
authors: Robert M
authors: RM
authors: Graham
authors: Jonathan G
authors: JG
authors: Seidman
authors: Christine E
authors: CE
authors: Seidman
authors: Nadia
authors: N
authors: Rosenthal
authors: Diane
authors: D
authors: Fatkin
authors: Richard P
authors: RP
authors: Harvey
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D009202:Cardiomyopathies / Q000235:genetics* / Q000378:metabolism; D002522:Chlorocebus aethiops; D005260:Female; D006330:Heart Defects, Congenital / Q000235:genetics* / Q000378:metabolism; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism; D010375:Pedigree; D059748:Proteolysis; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation; D055815:Young Adult
chemical_list: D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; D014157:Transcription Factors
keywords: NKX2-5; UBIQUITIN-proteasome system; dilated cardiomyopathy; gene mutations; transcription factors
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