Imai H T, Takahata N, Maruyama T, Daniel A, Honda T, Matsuda Y, Moriwaki K
National Institute of Genetics, Shizuoka-ken.
Jpn J Genet. 1988 Aug;63(4):313-42. doi: 10.1266/jjg.63.313.
As a theoretical standard for evaluating the high incidence of centric fusion in man and mouse, the relative probabilities of occurrence of reciprocal translocation (Tr), inversion (In) and centric fusion (Fu) were estimated based on the random-contact-and-exchange model. It was shown by this model that centric fusion was extremely rare (Fu = 0.0002, In = 0.0521 and Tr = 0.9477 for a human haploid karyotype). On the other hand, the occurrence rate of centric fusion in human newborn babies and European feral mice was about 500-1,000 times higher than the theoretically expected values, which is termed here the "fusion burst". We suggest that the fusion burst may be induced by the physical proximity of telomeres on the nuclear membrane, and the exchange of DNA strands by errors of telomere replication mechanisms. The cytogenetical significance of the fusion burst is discussed with regard to the minimum interaction hypothesis proposed by Imai et al. (1986). We suggest two closely linked possibilities that (1) the fusion burst in man and mouse can theoretically be placed in karyotype evolution as a transitional phase in the main stream of the fission-inversion cycle, and (2) it may be accelerated by some unknown (mutagenic) factors other than ionizing radiation.
作为评估人类和小鼠中着丝粒融合高发生率的理论标准，基于随机接触和交换模型估计了相互易位（Tr）、倒位（In）和着丝粒融合（Fu）发生的相对概率。该模型表明，着丝粒融合极为罕见（对于人类单倍体核型，Fu = 0.0002，In = 0.0521，Tr = 0.9477）。另一方面，人类新生儿和欧洲野生小鼠中的着丝粒融合发生率比理论预期值高出约500 - 1000倍，在此称为“融合爆发”。我们认为，融合爆发可能是由核膜上的端粒物理接近以及端粒复制机制错误导致的DNA链交换所诱发。结合今井等人（1986年）提出的最小相互作用假说，讨论了融合爆发的细胞遗传学意义。我们提出两个紧密相关的可能性：（1）理论上，人类和小鼠中的融合爆发在核型进化中可被视为裂变 - 倒位循环主流中的一个过渡阶段；（2）除了电离辐射外，它可能被某些未知的（诱变）因素加速。
