Vig B K, Swearngin S E
Department of Biology, University of Nevada, Reno 89557-0015.
Mutagenesis. 1986 Nov;1(6):461-5. doi: 10.1093/mutage/1.6.461.
Mouse L-cells were treated with bis-benzimidazole derivative (Hoechst 33258), caffeine and bleomycin in order to study genesis of laggards and micronuclei and formation of kinetochores as revealed by antikinetochore antibody staining. Apparently, the Hoechst 33258-induced decondensation experienced by the A:T-rich pericentric heterochromatin does not extend into the centromeric region and does not affect formation, physical appearance or function of kinetochores. The laggards induced by Hoechst 33258 are generally whole chromosome laggards which have antikinetochore antibody binding sites. These kinetochore-carrying laggards were seen to lie outside the spindle region in cells untreated with spindle inhibitors or hypotonic and stained differentially for spindle and chromosomes. Some micronuclei did not show kinetochore dots indicating their origin in acentric chromosome fragments. When cells were treated with caffeine or bleomycin, both types of micronuclei, namely those carrying kinetochores and those generated by acentric fragments, were seen. These results are interesting in that caffeine prevents the rejoining of chromosome breaks and one would expect only kinetochore-less micronuclei in caffeine-treated cells. It may mean that caffeine also induces aneuploidy. The L-cells carry minichromosomes which are no more than a pair of kinetochore dots. Such chromosomes, though detectable by antikinetochore antibody staining, may be missed in routine, acid-fixed, Giemsa-stained preparations.
为了研究落后染色体和微核的起源以及通过抗动粒抗体染色揭示的动粒形成，用双苯并咪唑衍生物（Hoechst 33258）、咖啡因和博来霉素处理小鼠L细胞。显然，富含A:T的着丝粒周围异染色质所经历的Hoechst 33258诱导的解聚不会延伸到着丝粒区域，也不会影响动粒的形成、外观或功能。Hoechst 33258诱导的落后染色体通常是具有抗动粒抗体结合位点的整条染色体落后。在用纺锤体抑制剂或低渗处理且纺锤体和染色体进行差异染色的未处理细胞中，可以看到这些带有动粒的落后染色体位于纺锤体区域之外。一些微核未显示出动粒点，表明它们起源于无着丝粒染色体片段。当用咖啡因或博来霉素处理细胞时，会观察到两种类型的微核，即带有动粒的微核和由无着丝粒片段产生的微核。这些结果很有趣，因为咖啡因会阻止染色体断裂的重新连接，人们预计在咖啡因处理的细胞中只会有无动粒微核。这可能意味着咖啡因也会诱导非整倍体。L细胞携带的微型染色体不超过一对动粒点。这样的染色体虽然可以通过抗动粒抗体染色检测到，但在常规的酸固定、吉姆萨染色制备中可能会被遗漏。
