Our lab has generated a transgenic mouse containing the DNA regulatory elements of the rat myosin light chain 1 genes. Although the transgene is properly expressed in a skeletal-muscle specific manner, it is expressed in a dramatic and unexpected gradient in muscles along the anteroposterior (head to tail) axis. The pattern arises early in development in a repetitive structure in the embryo called a somite, and persists in adults in skeletal muscle structures derived from somites. This likely reflects a general mechanism imparting positional information along the length of the organism, directing the formation of repeated muscles groups such as the intervertebrals found next to the ribs. l propose to use transgenic mice to identify the DNA sequences responsible for the transgene gradient and to investigate methylation as the mechanism giving rise to its formation.
