Bovero Stefano, Hankeln Thomas, Michailova Paraskeva, Schmidt Erwin, Sella Gabriella
Department of Animal and Human Biology, University of Turin, Italy.
Genetica. 2002 Aug;115(3):273-81. doi: 10.1023/a:1020697228525.
Two geographically distant populations of Chimnomus riparius (syn. C. thummi) from two environmentally polluted sites (Santena, Italy and Varna, Bulgaria) show numerous somatic and inherited chromosomal aberrations (inversions, deletions and deficiencies). Fifty-five percent of the observed breakpoints occurred in at least two larvae from both populations. Breakpoints occurring twice or more were considered as 'common' structural chromosomal breakpoints. We tested whether such common breakpoints in larvae of the two polluted populations had a random chromosomal distribution or occurred preferentially in specific heterochromatic regions. Distribution of common breakpoints was not random, and proximal regions of first and third chromosome had significantly more common breakpoints than distal ones. By FISH we identified and mapped 56 chromosomal sections containing clusters of two tandem-repetitive satellite DNA families called Hinf and Alu elements. Like the common breakpoints, these repetitive DNA clusters appeared to be significantly more abundant in regions of constitutive heterochromatin such as the pericentromeric regions, while in distal sections of chromosomal arms they were rare or absent. Twenty-four out of 45 common breakpoints (i.e., 53.3%) occurred in cytogenetic sections where Alu and Hinf satellite DNA probes hybridized. The frequency of co-localization between common breakpoints and repetitive DNA hybridization signals was significantly higher than expected by chance. We hypothesize that spontaneous or induced breaks occur more frequently in sections containing blocks of repetitive DNA.
来自两个受环境污染地点（意大利的桑泰纳和保加利亚的瓦尔纳）的地理上相距遥远的两个河岸摇蚊种群（学名Chimnomus riparius，同义词C. thummi）表现出众多体细胞和遗传染色体畸变（倒位、缺失和缺陷）。在两个种群中，至少有两只幼虫出现了55%的观察到的断点。出现两次或更多次的断点被视为“常见”的结构性染色体断点。我们测试了这两个受污染种群幼虫中的此类常见断点是具有随机的染色体分布，还是优先发生在特定的异染色质区域。常见断点的分布并非随机，第一和第三条染色体的近端区域比远端区域有明显更多的常见断点。通过荧光原位杂交（FISH），我们鉴定并绘制了56个染色体区域，这些区域包含两个串联重复卫星DNA家族（称为Hinf和Alu元件）的簇。与常见断点一样，这些重复DNA簇在组成型异染色质区域（如着丝粒周围区域）似乎明显更为丰富，而在染色体臂的远端区域则很少见或不存在。45个常见断点中有24个（即53.3%）发生在Alu和Hinf卫星DNA探针杂交的细胞遗传学区域。常见断点与重复DNA杂交信号之间的共定位频率明显高于偶然预期。我们推测，自发或诱导的断裂在含有重复DNA块的区域更频繁发生。
