Developmental changes in the chromatin of the brain of the rat: analysis by nick-translation.

Nick translation of nuclei of the brain of 3- 14- and 30-day old rats was carried out following their digestion by DNase I. The incorporation of 3H-dTMP at 14- and 30-day is significantly lower than at 3-day. This may be due to a lower proportion of active chromatin (DNase I hypersensitive sites) and condensation of chromatin with progressive development. When nuclei were digested by EcoRI and then nick-translated, the incorporation of 3H-dTMP showed the same pattern. Since the EcoRI sites are believed to be randomly distributed, the overall conformation of chromatin including the DNase I sensitive sites seems to undergo increasing compaction with development.