Cytogenetic analysis of heteromorphic short arm of 15p+ in a human diploid cell strain, TIG-7

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The heteromorphic chromosome 15 with an extra short arm (15p+) of a human male diploid cell strain, TIG-7, was analyzed using chromosome banding, flow karyotyping and fluorescence in situ hybridization (FISH). Ag-NORs were detected in the proximal region close to the centromere and in the distal telomeric end of the short arm, although ribosomal RNA gene (rDNA) was recognized on the whole short arm of the 15p+ with FISH. The extra region consisted of G+C-rich DNA, which was not detected in other rDNA regions, i.e. secondary constrictions in D- and G-group chromosomes in this cell strain, when the chromomycin A_3 fluorescence pattern was compared with the bivariate flow karyotype. Furthermore, a demethylating agent, 5-azacytidine induced marked chromatin decondensation in the 15p+ region. These findings indicated that a possible mechanism responsible for amplification and inactivation of the specific rDNA cluster, is related to DNA methylation in this chromosome.
財団法人染色体学会の論文