The Heterochromatin Condensation State in Peripheral “Gene Poor” and Central “Gene Rich” Nuclear Regions of Less Differentiated and Mature Human Leukemic Cells: A Mini-Review with Additional Original Observations

In the morphological cytology the heterochromatin is one of very useful tools for the cell identification including the differentiation and maturation stage. However, the heterochromatin condensation state was less studied although it appeared to be different in “gene rich” central and “gene poor” peripheral nuclear regions. The heavy heterochromatin condensation state in the central “gene rich” nuclear regions might reflect a marked structural stability and protect the genomic integrity. It must be also noted that the heterochromatin condensation state in these nuclear regions is more variable than in the nuclear periphery because of the presence of more as well as less condensed heterochromatin territories. On the other hand, the heterochromatin condensation state in the nuclear periphery markedly increases during the cell differentiation and maturation. In fully differentiated and mature cells the heavy heterochromatin condensation state is similar in both central and peripheral nuclear regions. The resulting ratio of the heterochromatin condensation state in central nuclear regions to the nuclear periphery is higher in less differentiated cells and then decreases during the maturation (terminal differentiation) process. That ratio facilitates to compare cells in different differentiation or maturation stages of various cell lineages because the estimated arbitrary density units are frequently variable depending on the background of the cell surrounding.