The Mechanism of Hyper-radiosensitivity Expressed in Ataxia telangiectasia Disease.

为了鉴定一名遗传性疾病共济失调毛细血管扩张症（ataxia毛细血管扩张症）患者细胞中携带突变基因的染色体，我们通过微细胞融合进行了染色体转移实验。通过微细胞融合将来自正常人成纤维细胞的单个psv2neo标记染色体（11或12）导入AT-D细胞，并分离出对抗生素G418耐药的克隆。所有含有11号染色体额外拷贝数的3个杂交克隆都显示出野生型细胞对x射线杀伤的抗性恢复，而所有含有2号染色体额外拷贝数的3个杂交克隆都像亲本AT细胞一样保持高辐射敏感性。另一方面，将第11号染色体引入AT5BIVA细胞后，x射线诱导的染色质型畸变被抑制到对照水平，而AT5BIVA细胞诱导的染色质型畸变频率比对照细胞高约3.4倍。然而，这种显著的减少并没有在所有含有12号染色体额外拷贝的杂交克隆中观察到。引入染色体对染色体畸变的抑制作用似乎在畸变类型上有所不同。将11号染色体引入AT5BIVA细胞有效地抑制了间隙和断裂的频率，但没有抑制交换。X-ray-induced的平均值0.45铬酸交流AT11/3克隆仍然显示水平父母AT5BIVA细胞类似,虽然差距和优惠的平均值分别为1.2和1.8,与那些在控制结果表明,d细胞的基因缺陷我也位于11号染色体,由于先前已经表明遗传连锁分析缺陷基因的互补群坐落在这条染色体。

In order to identify the human chromosome which carries a mutated gene in cells from a patient with the hereditary disorder ataxia telangiectasia belonging to complementation group D (AT-D), we performed chromosome transfer experiments via microcell fusion. A single, pSV2neo-tagged chromosome, either 11 or 12, derived from normal human fibroblasts was introduced into AT-D cells by microcell fusion, and clones which were resistant to the antibiotic G418 were isolated. All 3 hybrid clones containing an additional copy number of chromosome 11 showed a restoration of the resistance of wild-type cells to killing by X-irradiaiton, whereas all 3 hybrid clones containing an additional copy number of chromosome 2 remained hyperradiosensitive, like the parental AT cells. On the other hand, the introduction ofchromosome 11 into the AT5BIVA cells suppressed X-ray-induced chromated-type aberrations to the control level, while the AT5BIVA cells was about 3.4-fold higher in the frequency of induced chromated-type aberrations than control cells. However, such a remarkable reduction was not observed in all hybrid clones containing an additional copy of chromosome 12. -The suppressive effect of chromosome aberrations by introducing chromosome -seemed to be different in types of aberrations. The introduction of chromosome 11 into the AT5BIVA cells efficiently suppressed the frequencies of gaps and breaks but not exchanges. The mean value of X-ray-induced chromated exchanges in the AT11/3 clone remained 0.45 showing a similar level in the parental AT5BIVA cells, although the mean values of gaps and breaks were 1.2 and 1.8 which were comparable to those in controls The results indicate that a defective gene of AT-D cells i also located on chromosome 11, since a genetic linkage analysis has previously suggested that a defective gene of its complementation group A is located on this chromosome.