Analysis of chromatin of skeletal muscle of developing rats using micrococcal nuclease and DNase I

Conformational changes in the chromatin of skeletal muscle of 3-, 14- and 30 day-old developing rats have been studied using DNase I and micrococcal nuclease (MCN). Purified nuclei were digested separately by MCN and DNase I. The rate and extent of digestion by MCN decreases gradually as development proceeds. The electrophoretic pattern of MCN digested DNA, however, shows no change. The kinetics of digestion of nuclei by DNase I show no change with development. However, the electrophoretic pattern of DNase I digested DNA shows a gradual decrease in the amount of 10-30 bp fragments with progressive development. These studies show that the chromatin of the skeletal muscle undergoes certain conformational changes during postnatal development, and such changes in chromatin may be necessary for terminal differentiation of this tissue.