Chromosomes of older humans are more prone to aminopterine-induced breakage.
Chromosomes of older humans are more prone to aminopterine-induced breakage.
复制标题
老年人的染色体更容易发生氨基蝶呤引起的断裂。
DOI：
10.1073/pnas.86.4.1302
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发表时间：
1989
影响因子：
11.1
通讯作者：
Siniscalco,M
中科院分区：
文献类型：
--
作者：
Esposito,D;Fassina,G;Szabo,P;DeAngelis,P;Rodgers,L;Weksler,M;Siniscalco,M
我们采用了一种简化的“细胞杂交共转移方法”来检验这一假设，即来自老年人的人类淋巴细胞具有更高的染色体不稳定性。将“老年”男性个体和“年轻”对照组的外周血淋巴细胞与中国仓鼠细胞系(CHO-YH21)融合，得到10个抗HAT的鼠类-人克隆，22个来自青年对照组(HAT=次黄嘌呤/氨基蝶呤/胸腺嘧啶核苷)。分析了这两系列杂交克隆对葡萄糖-6-磷酸脱氢酶和由位于X染色体两端的两个人类X染色体连锁标记12E7鉴定的表面抗原MIC2的保留情况。来自年轻对照的带有X染色体的细胞杂交克隆在大约70%的细胞中保留了这两种标记。相比之下，来自老捐赠者的X染色体的细胞杂交克隆只在30%的细胞中保留了MIC2标记。时隙印迹杂交研究已经证实，观察到的MIC2标记的丢失是由于编码基因的丢失，而不是由于其表达受到抑制。与X染色体其他区域特异的分子探针进行的类似杂交研究表明，染色体断裂位点具有优势。来自老年供者的T淋巴细胞对氨基喋呤的LD50也显著低于用于生长杂交种的HAT培养液中该药物的浓度，这表明在老年供者的X染色体上观察到的较高水平的基因丢失可能与他们对氨基喋呤的断裂效应的敏感性增加直接相关。我们推测，在“老年”X染色体上观察到的较高的染色体断裂率和标记丢失率可能是随着年龄的增长在构成染色体脆性部位积累的“分子疤痕”的结果。
We have adopted a simplified version of the "cell hybrid cotransfer method" to test the hypothesis that human lymphocytes derived from elderly individuals have a higher chromosome instability. Peripheral blood lymphocytes from "old" male individuals and "young" controls were fused with a Chinese hamster cell line (CHO-YH21), yielding 10 HAT-resistant rodent-human clones from the old propositi and 22 from the young controls (HAT = hypoxanthine/aminopterin/thymidine). Both series of hybrid clones were analyzed with respect to the retention of the enzyme glucose-6-phosphate dehydrogenase and the surface antigen MIC2 identified by monoclonal antibody 12E7, two human X chromosome-linked markers located at opposite ends of the X chromosome. Cell hybrid clones with an X chromosome from a young control retained both markers in about 70% of the cells. In contrast, cell hybrid clones with an X chromosome from an old donor retained the MIC2 marker in only 30% of their cells. Slot-blot hybridization studies have established that the observed loss of the MIC2 marker is due to loss of the coding gene, not to suppression of its expression. Similar hybridization studies with molecular probes specific for other regions of the X chromosome suggest preferential chromosomal breakage sites. T lymphocytes from old donors were also found to have an LD50 for aminopterine significantly lower than the concentration of this drug in the HAT medium used to grow the hybrids, suggesting that the higher level of gene loss observed in the X chromosomes from old donors may be directly related to their increased sensitivity to the clastogenic effect of aminopterine. We speculate that the higher rate of chromosomal breakage and of marker loss observed along the "old-age" X chromosomes could be the result of "molecular scars" accumulated with aging at sites of constitutive chromosomal fragility.