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

TitleTargeted homozygous deletion of M-band titin in cardiomyocytes prevents sarcomere formation.
Publication TypeJournal Article
Year of Publication2006
AuthorsMusa H, Meek S, Gautel M, Peddie D, Smith AG, Peckham M
JournalJ Cell Sci
IssuePt 20
Date Published2006 Oct 15
KeywordsAnimals, Cell Differentiation, Cell Line, Connectin, Embryonic Stem Cells, Gene Deletion, Heterozygote, Homozygote, Mice, Microscopy, Confocal, Models, Genetic, Muscle Proteins, Myocytes, Cardiac, Myofibrils, Protein Kinases, Proteins, Sarcomeres, Transcription Factors

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.

Alternate JournalJ. Cell. Sci.
PubMed ID17038546
Grant ListG0200496 / / Medical Research Council / United Kingdom
/ / Wellcome Trust / United Kingdom