Titre : | Targeted homozygous deletion of M-band titin in cardiomyocytes abrogates sarcomere formation (abstract : congrès international de Myologie, 2005) |
contenu dans : | |
Auteurs : | Congrès international de myologie 2005 (International Congress of Myology 2005; 9-13 mai 2005; Nantes, France) ; Musa H ; Pechkham M ; Meek S ; Smith A ; Gautel M |
Type de document : | Article |
Année de publication : | 2005 |
Pages : | p. 88 |
Langues: | Anglais |
Mots-clés : | colloque ; mutation génétique ; myocarde ; myofibrille ; myogenèse ; myosine ; phosphorylation ; sarcomère ; souris ; titine |
Résumé : |
Communication n° 582. Introduction : Sarcomere organisation is a complex and poorly understood process of which titin is believed to play a pivotal role in. The M-band portion of the titin contains a kinase domain, phosphorylation sites, and multiple binding sites for structural and signalling proteins like myomesin or FHL2/DRAL, respectively. Missense mutations or deletions in M-line titin or its ligands are the cause of genetic myopathies like limb-girdle muscular dystrophy or tibial anterior muscular dystrophy. Objective : To create and investigate the effect on myofibrillogenesis of a homozygous targeted deletion of the titin M-band in a mouse embryonic stem (ES) cell line. Methods : Wild type and targeted ES cells were cultured and differentiated in hanging drops to form embryoid bodies (for 2 days; EBs), then in suspension bacteriological dishes for a further 3 days, before separately plating on to matrigel coated cover-slips, allowed to attach and grow out into cardiomyocytes and myofibrillogenesis was investigated. Results : Striated sarcomeres were completely lost in targeted cells in contrast to wild-type cells, although sarcomeric proteins (myosin and myomesin) remained. Z-disk, I-band and A-band titin was present but myosin remains in primitive structures that most closely resemble non-striated myofibrils, and fails to be crosslinked by myomesin. Surprisingly, the maturation of Z-disks is blocked, with Z-disk titin, alpha-actinin and obscurin all remaining in primitive, dot-shaped Z-disk precursors aligned along stress-fibre like structures. The failure to assemble striated acto-myosin assemblies is reflected in lack of spontaneous beating in these cardiomyocytes, a regular feature of wild-type cells Conclusion : These findings suggest that M-line titin is not only crucially important for myosin filament assembly and M-line formation, but that these steps are also required for the maturation of the Z-disk. . |