Comparative study of human and chimpanzee chromosomes by fluorescence in situ hybridization

人类2号染色体是人类染色体组型与类人猿染色体组型之间唯一明显的例外（Wienberg et al.1990，1992）。根据人类和类人猿染色体带型的比较，人类2号染色体被认为是由两条祖先类人猿染色体融合而成的。这已经被分子数据证实;通过DNA微文库的比较染色体作图，人类2 q12-q14区域与黑猩猩（Pan troglodytes，PTR）12 p和13 p同源。此外，端粒-端粒融合点已被证实定位于染色体带2 q13。最近，Takahashi等（1995）构建了一个包含434个粘粒标记的人类2号染色体高分辨率细胞遗传学图谱。本文报道了用缺口平移法用生物素-14-dATP或地高辛-11-dUTP标记的粘粒标记物在2 q12 -14区域的物理顺序。对放线菌素D解致密的中期染色体和DNA纤维进行双色FISH排序。DNA纤维的制备是我们对标准方案的修改（Suto等人，1996年）。在人和黑猩猩的染色体上共定位了36个染色体。17个人类2号染色体起源的标记位于PTR 12短臂，和19个PTR 13短臂。黑猩猩染色体上的克隆顺序与人类2号染色体相同。结果表明，人类2号染色体是由两个祖先猿类染色体之间的串联融合产生的，并且祖先基因组的组织已经相当保守。这一区域在类人猿中的比较作图可能有助于确定进化过程中染色体重组的年代。

Human chromosome 2 is the only obvious exception from the chromosomal homologies between the human karyotype and that of the great apes (Wienberg et al.1990,1992). Human chromosome 2 has been described that it arose out of the fusion of two ancestral ape chromosomes on the basis of comparisons of chromosome banding patterns between human and great apes. This has been confirmed by molecular data ; human 2q12-q14 region is homologous with chimpanzee (Pan troglodytes, PTR) 12p and 13p by comparative chromosome mapping with DNA microlibraries. Furthermore, the telomere-to-telomere fusion point has been conjectured to be localized in chromosomal band 2q13. Recently a high resolution cytogenetic map of human chromosome 2 with 434 cosmid makers was constructed by Takahashi et al. (1995). The present report describes the physical order of cosmid makers in the region 2q12-14 using FISH.The cosmids were labeled with either biotin-14-dATP or digoxigenin-11-dUTP by nick-translation. Two-color FISH for ordering was performed on metaphase chromosomes decondensed by actinomycin D and on DNA fibers. Preparation of DNA fibers was our modifications of the standard protocol (Suto et al., 1996). Totally 36 cosmids were localized on human and chimpanzee chromosomes. Seventeen human chromosome 2-originated markers were located to PTR 12 short arm, and nineteen to PTR 13 short arm. The order of clones on chimpanzee chromosomes was identical to that of human chromosome 2. The results suggest that human chromosome 2 arose out of tandem fusion between two ancestral ape-type chromosomes, and that the organization of the ancestral genome has been considerably conserved. Comparative mapping of this region among great apes may contribute to the dating of chromosomal reorganization in evolution.