Phenomenon of selective staining of pericentromeric heterochromatin regions in chromosomes from spontaneously dividing cells by the acridine orange fluorochrome

A novel phenomenon of unusual selective acridine orange (AO) staining of pericentromeric heterochromatin regions (HRs) in chromosomal preparations from tissue with known spontaneous mitotic activity (chorionic villi, placenta, embryonic tissues, bone marrow, and testes), as well as embryonic stem cells, is described. Staining with 0.01% AO in a citric-phosphate (pH 5.5) or sodium phosphate (pH 7.0) buffer solution allows the HRs of human chromosomes (1q12, 9q12, 13p11.2, 14p11.2, 15p11.2, 16q11.2, 21p11.2, 22p11.2, and Yq12) and pericentromeric HRs of mouse chromosomes to be reliably detected by the red fluorescence of AO. This method of AO staining does not require any pretreatment. Explanations for metachromatic AO staining of polymorphic pericentromeric HRs in chromosomes of spontaneously dividing cells are suggested. A high reproducibility of the specific AO staining makes it possible to suggest its using as a reliable quick method for detection of polymorphic HRs of human chromosomes in cytogenetic prenatal diagnosis and oncohematology.