CB-FISH法检测人体内嵌合的21号染色体非整倍体

目的　探讨 2 1三体患者体内二倍体细胞增多的机理。方法　用松胞素 - B诱导的双核细胞荧光原位杂交技术 ,对人体内 2 1号染色体非整倍体和培养细胞中 2 1号染色体分离异常的发生率进行检测。结果　 2 1三体患者体内 ,二倍体细胞率 (16 .90‰± 10 .70‰ )远高于 2 1四体细胞率 (0 .42‰± 0 .6 4‰ ) (P=0 .0 0 0 )。在培养的正常人和 2 1三体患者细胞中 ,2 1号染色体不分离率 (3.6 9‰± 2 .5 0‰和 8.2 2‰±5 .5 4‰ )显著高于丢失率 (0 .10‰± 0 .30‰和 0 .43‰± 0 .49‰ ) (P=0 .0 0 0 )。结论　 2 1三体患者体内较高比例的二倍体细胞源于因三体细胞中 2 1号染色体分离异常而形成的二倍体细胞的逐渐积累

Detection of mosaic chromosome 21 aneuploidy in vivo with CB-FISH method

OBJECTIVE: To explore the mechanism by which the ratio of mosaic diploid cells in vivo increased in trisomy 21 cases. METHODS: Fluorescence in situ hybridization (FISH) with pericentric DNA probes specific to human chromosome 21 to the binucleated cells cytokinesis- blocked by cytochalasin-B(CB), namely, CB-FISH method. RESULTS: The mean frequency of diploid cells (1.69%+/-1.07%) was significantly higher than that of tetrasomy 21 cells(0.042%+/-0.064%)(P=0.000) in 12 trisomy 21 cases aged 0-9 years (mean 4 years) in vivo; whereas the incidence of spontaneous monosomy 21 cells (0. 265%+/-0.13%) was close to the frequency of trisomy 21 cells (0. 225%+/-0.184%) in 20 control individuals aged 0-10 years (mean 5 years). The frequency of cells undergone chromosome 21 nondisjunction was 0.822%+/-0.554% in cultured trisomy 21 cells, which was significantly higher than that in the cultured diploid cells (0.369%+/-0.25%). However, the rates of cells with chromosome 21 loss in the two cultured cell lines (0.01%+/-0.03% vs 0.043%+/-0.049%) were not significantly different. In both cultured cell lines, chromosome 21 nondisjunction occurred more frequently than loss. CONCLUSION: The increased frequency of diploidies in trisomy 21 cases may result from the accumulation of diploid cells originating from malsegregation of chromosome 21 in trisomic cells rather than the increase of chromosome 21 loss.