Interphase genome as the active space: chromatin dynamics during chick embryo chondrogenesis.

The rearrangement of the chromatin that takes place during cytodifferentiation was studied using TV image analysis in chick limb bud cartilage stained for DNA. The redistribution of the chromatin was compatible with the Rabl orientation: chromatin was extended radially from the centromeric ring to the telomere pole in young chondroblasts, and contracted back in ageing chondrocytes. The direction and gradient of this redistribution correlate with the changes in DNA content within the chromocentres formed by pericentromeric heterochromatin. In turn, intercalary heterochromatin regulates the condensation of the adjacent euchromatin depending upon the position in this radial-polar gradient.