In vivo expression and molecular characterization of the porcine slow-myosin heavy chain.

We report on the molecular characterization of the porcine slow-myosin heavy chain (HC) beta gene and the isolation of its 5' end cDNA. In vivo expression study, by in situ hybridization and histochemistry, revealed a highly regular rosette pattern of fiber arrangement, with a slow fiber occupying the central core, in all the skeletal muscles examined. This feature can be advantageous in the distinction of primary and secondary fibers in myogenic lineage studies. In the neonatal heart, beta isoform expression is diffuse, with higher expression occurring in the ventricle than in the atrium. Transient transfection assays showed the porcine promoter functions in a muscle- and differentiation stage-specific manner. In the 5' regulatory region are several putative positive and negative regulatory elements, including a positive and a negative element in close proximity to each other in intron 1.