Faculty Bibliography

To elucidate the role of cardiac myosin-binding protein-C (MyBP-C) in myocardial structure and function, we have produced mice expressing altered forms of this sarcomere protein. The engineered mutations encode truncated forms of MyBP-C in which the cardiac myosin heavy chain-binding and titin-binding domain has been replaced with novel amino acid residues. Analogous heterozygous defects in humans cause hypertrophic cardiomyopathy. Mice that are homozygous for the mutated MyBP-C alleles express less than 10% of truncated protein in M-bands of otherwise normal sarcomeres. Homozygous mice bearing mutated MyBP-C alleles are viable but exhibit neonatal onset of a progressive dilated cardiomyopathy with prominent histopathology of myocyte hypertrophy, myofibrillar disarray, fibrosis, and dystrophic calcification. Echocardiography of homozygous mutant mice showed left ventricular dilation and reduced contractile function at birth; myocardial hypertrophy increased as the animals matured. Left-ventricular pressure-volume analyses in adult homozygous mutant mice demonstrated depressed systolic contractility with diastolic dysfunction. These data revise our understanding of the role that MyBP-C plays in myofibrillogenesis during cardiac development and indicate the importance of this protein for long-term sarcomere function and normal cardiac morphology. We also propose that mice bearing homozygous familial hypertrophic cardiomyopathy-causing mutations may provide useful tools for predicting the severity of disease that these mutations will cause in humans

We used ultrasound image-guided injections of high-titer retroviral vectors to obtain widespread introduction of genes into the mouse nervous system in utero as early as embryonic day 8.5 (E8.5). The vectors used included internal promoters that substantially improved proviral gene expression in the ventricular zone of the brain. To demonstrate the utility of this system, we extended our previous work in vitro by infecting the telencephalon in vivo as early as E8. 5 with a virus expressing Sonic Hedgehog. Infected embryos showed gross morphological brain defects, as well as ectopic expression of ventral telencephalic markers characteristic of either the medial or lateral ganglionic eminences