Exon-skipped dystrophins for treatment of Duchenne muscular dystrophy: mass spectrometry mapping of most exons and cooperative domain designs based on single molecule mechanics.

Force-bearing linkages between the cytoskeleton and extracellular matrix are clearly important to normal cell viability-as is evident in a disease such as Duchenne muscular dystrophy (DMD) which arises in the absence of the linkage protein dystrophin. Therapeutic approaches to DMD include antisense-mediated skipping of exons to delete nonsense mutations while maintaining reading frame, but the structure and stability of the resulting proteins are generally unclear. Here we use mass spectrometry to detect most dystrophin exons, and we express and physically characterize dystrophin "nano"-constructs based on multiexon deletions that might find use in a large percentage of DMD patients.

Embryonic cardiomyocytes beat best on a matrix with heart-like elasticity: scar-like rigidity inhibits beating.

Fibrotic rigidification following a myocardial infarct is known to impair cardiac output, and it is also known that cardiomyocytes on rigid culture substrates show a progressive loss of rhythmic beating. Here, isolated embryonic cardiomyocytes cultured on a series of flexible substrates show that matrices that mimic the elasticity of the developing myocardial microenvironment are optimal for transmitting contractile work to the matrix and for promoting actomyosin striation and 1-Hz beating. On hard matrices that mechanically mimic a post-infarct fibrotic scar, cells overstrain themselves, lack striated myofibrils and stop beating; on very soft matrices, cells preserve contractile beating for days in culture but do very little work.