Functional characterization of a novel mutation in NKX2-5 associated with congenital heart disease and adult-onset cardiomyopathy

Circ Cardiovasc Genet. 2013 Jun;6(3):238-47. doi: 10.1161/CIRCGENETICS.113.000057. Epub 2013 May 9.


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.

Methods and 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.

Keywords: NKX2-5; UBIQUITIN-proteasome system; dilated cardiomyopathy; gene mutations; transcription factors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Age of Onset
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • COS Cells
  • Cardiomyopathies / genetics*
  • Cardiomyopathies / metabolism
  • Chlorocebus aethiops
  • Female
  • Heart Defects, Congenital / genetics*
  • Heart Defects, Congenital / metabolism
  • Homeobox Protein Nkx-2.5
  • Homeodomain Proteins / chemistry
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism*
  • Humans
  • Male
  • Middle Aged
  • Molecular Sequence Data
  • Mutation
  • Myocytes, Cardiac / metabolism
  • Pedigree
  • Proteolysis
  • Sequence Alignment
  • Transcription Factors / chemistry
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism*
  • Transcriptional Activation
  • Young Adult


  • Homeobox Protein Nkx-2.5
  • Homeodomain Proteins
  • NKX2-5 protein, human
  • Transcription Factors