Targeted homozygous deletion of M-band titin in cardiomyocytes prevents sarcomere formation

Hanny Musa, Stephen Meek, Mathias Gautel, Dianna Peddie, Andrew J. H. Smith, Michelle Peckham

Research output: Contribution to journalArticlepeer-review

Abstract

Titin, a multifunctional protein that stretches from the Z-disk to the M-band in heart and skeletal muscle, contains a kinase domain, phosphorylation sites and multiple binding sites for structural and signalling proteins in the M-band. To determine whether this region is crucial for normal sarcomere development, we created mouse embryonic stem cell (ES) lines in which either one or both alleles contained a targeted deletion of the entire M-band-coding region, leaving Z-disk-binding and myosin-filament-binding sites intact. ES cells were differentiated into cardiomyocytes, and myofibrillogenesis investigated by immunofluorescence microscopy. Surprisingly, deletion of one allele did not markedly affect differentiation into cardiomyocytes, suggesting that a single intact copy of the titin gene is sufficient for normal myofibrillogenesis. By contrast, deletion of both alleles resulted in a failure of differentiation beyond an early stage of myofibrillogenesis. Sarcomeric myosin remained in non-striated structures, Z-disk proteins, such as alpha-actinin, were mainly found in primitive dot-like structures on actin stress fibres, M-band-associated proteins (myomesin, obscurin, Nbr1, p62 and MURF2) remained punctate. These results show that integration of the M-band region of titin is required for myosin filament assembly, M-band formation and maturation of the Z-disk.
Original languageEnglish
Article number20
Pages (from-to)4322-31
Number of pages10
JournalJournal of Cell Science
Volume119
DOIs
Publication statusPublished - Oct 2006

Keywords

  • Animals
  • Cell Differentiation/genetics
  • Cell Differentiation/physiology
  • Cell Line
  • Connectin
  • Embryonic Stem Cells/cytology
  • Embryonic Stem Cells/metabolism
  • Gene Deletion
  • Heterozygote
  • Homozygote
  • Mice
  • Microscopy, Confocal
  • Models, Genetic
  • Muscle Proteins/genetics
  • Muscle Proteins/metabolism
  • Muscle Proteins/physiology
  • Myocytes, Cardiac/cytology
  • Myocytes, Cardiac/metabolism
  • Myofibrils/genetics
  • Myofibrils/metabolism
  • Protein Kinases/genetics
  • Protein Kinases/metabolism
  • Protein Kinases/physiology
  • Proteins/metabolism
  • Sarcomeres/metabolism
  • Transcription Factors/metabolism

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