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A single serine in the carboxyl terminus of cardiac essential myosin light chain-1 controls cardiomyocyte contractility in vivo.

Although it is well known that mutations in the cardiac essential myosin light chain-1 (cmlc-1) gene can cause hypertrophic cardiomyopathy, the precise in vivo structural and functional roles of cMLC-1 in the heart are only poorly understood. We have isolated the zebrafish mutant lazy susan (laz), which displays severely reduced contractility of both heart chambers. By positional cloning, we identified a nonsense mutation within the zebrafish cmlc-1 gene to be responsible for the laz phenotype, leading to expression of a carboxyl-terminally truncated cMLC-1. Whereas complete loss of cMLC-1 leads to cardiac acontractility attributable to impaired cardiac sarcomerogenesis, expression of a carboxyl-terminally truncated cMLC-1 in laz mutant hearts is sufficient for normal cardiac sarcomerogenesis but severely impairs cardiac contractility in a cell-autonomous fashion. Whereas overexpression of wild-type cMLC-1 restores contractility of laz mutant cardiomyocytes, overexpression of phosphorylation site serine 195-deficient cMLC-1 (cMLC-1(S195A)) does not reconstitute cardiac contractility in laz mutant cardiomyocytes. By contrast, introduction of a phosphomimetic amino acid on position 195 (cMLC-1(S195D)) rescues cardiomyocyte contractility, demonstrating for the first time an essential role of the carboxyl terminus and especially of serine 195 of cMLC-1 in the regulation of cardiac contractility.

Pubmed ID: 19168438


  • Meder B
  • Laufer C
  • Hassel D
  • Just S
  • Marquart S
  • Vogel B
  • Hess A
  • Fishman MC
  • Katus HA
  • Rottbauer W


Circulation research

Publication Data

March 13, 2009

Associated Grants


Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cloning, Molecular
  • Codon, Nonsense
  • Ethylnitrosourea
  • Gene Expression Regulation, Developmental
  • Genotype
  • Heart
  • Models, Molecular
  • Molecular Conformation
  • Molecular Sequence Data
  • Muscle Strength
  • Mutagens
  • Myocardial Contraction
  • Myocytes, Cardiac
  • Myosin Light Chains
  • Phenotype
  • Phosphorylation
  • Protein Stability
  • Protein Structure, Tertiary
  • Sarcomeres
  • Sequence Homology, Amino Acid
  • Serine
  • Time Factors
  • Zebrafish
  • Zebrafish Proteins