INTERACTIVE COMPUTER-ASSISTED ANALYSIS OF CHROMOSOME-1 COLOCALIZATIONWITH NUCLEOLI

The applications of DNA cloning and fluorescent in situ hybridization (FISH) techniques have strengthened the hypothesis of an ordered chrom atin structure in interphase nuclei, strongly suspected to vary with f unctional state. The nonrandom distribution of the centromeres and the ir dynamic rearrangement during the cell cycle have been well document ed. A close proximity of specific centromeres to nucleoli has also bee n reported, but the functional meaning of this association is still un known. In order to investigate whether the chromosome 1 centromere reg ion to nucleolus association depends on the cell cycle and chromosome status, we combined FISH of probes specific for the 1q12 region with K i-67 nucleolar antigen fluorescent immunocytochemical (FICC) detection on the MCF-7 human breast cancer cell line and on the MRC-5 normal fi broblastic cell line. Both FISH and FICC signals were interactively lo calized in a one-step fluorescent microscopic observation and further analyzed using the Highly Optimized Microscope Environment (HOME) grap hics microscope workstation, which provided computerized interactive m arking of 1q12 to nucleolus associations (1q12-nu) at the individual n ucleus and nucleolus levels. This study confirms that centromeric regi ons, other than those adjacent to the major ribosomal cistrons, contri bute to the perinucleolar chromatin and demonstrate that, during the c ell cycle, the heterochromatic band 1q12 is dynamically rearranged wit h regard to both the nuclear volume and the nucleoli. A relationship b etween the association of the chromosome 1 pericentromeric region with nucleoli and the nucleolar transcriptional activity is also strongly suggested. (C) 1994 Wiley-Liss, Inc.