Postlethwait J H, Yan Y L, Gates M A, Horne S, Amores A, Brownlie A, Donovan A, Egan E S, Force A, Gong Z, Goutel C, Fritz A, Kelsh R, Knapik E, Liao E, Paw B, Ransom D, Singer A, Thomson M, Abduljabbar T S, Yelick P, Beier D, Joly J S, Larhammar D, Rosa F, Westerfield M, Zon L I, Johnson S L, Talbot W S
Institute of Neuroscience, University of Oregon, Eugene 97403-1254, USA.
Nat Genet. 1998 Apr;18(4):345-9. doi: 10.1038/ng0498-345.
In chordate phylogeny, changes in the nervous system, jaws, and appendages transformed meek filter feeders into fearsome predators. Gene duplication is thought to promote such innovation. Vertebrate ancestors probably had single copies of genes now found in multiple copies in vertebrates and gene maps suggest that this occurred by polyploidization. It has been suggested that one genome duplication event occurred before, and one after the divergence of ray-finned and lobe-finned fishes. Holland et al., however, have argued that because various vertebrates have several HOX clusters, two rounds of duplication occurred before the origin of jawed fishes. Such gene-number data, however, do not distinguish between tandem duplications and polyploidization events, nor whether independent duplications occurred in different lineages. To investigate these matters, we mapped 144 zebrafish genes and compared the resulting map with mammalian maps. Comparison revealed large conserved chromosome segments. Because duplicated chromosome segments in zebrafish often correspond with specific chromosome segments in mammals, it is likely that two polyploidization events occurred prior to the divergence of fish and mammal lineages. This zebrafish gene map will facilitate molecular identification of mutated zebrafish genes, which can suggest functions for human genes known only by sequence.
在脊索动物系统发育过程中，神经系统、颌骨和附肢的变化将温顺的滤食动物转变为可怕的捕食者。基因复制被认为促进了这种创新。脊椎动物的祖先可能拥有现在在脊椎动物中以多个拷贝形式存在的基因的单拷贝，基因图谱表明这是通过多倍体化发生的。有人提出，在辐鳍鱼和肉鳍鱼分化之前发生了一次基因组复制事件，之后又发生了一次。然而，霍兰德等人认为，由于各种脊椎动物都有几个HOX基因簇，两轮复制发生在有颌鱼类起源之前。然而，这样的基因数量数据并不能区分串联复制和多倍体化事件，也不能区分不同谱系中是否发生了独立复制。为了研究这些问题，我们绘制了144个斑马鱼基因的图谱，并将所得图谱与哺乳动物图谱进行了比较。比较揭示了大片保守的染色体片段。由于斑马鱼中复制的染色体片段通常与哺乳动物中的特定染色体片段相对应，很可能在鱼类和哺乳动物谱系分化之前发生了两次多倍体化事件。这个斑马鱼基因图谱将有助于对突变的斑马鱼基因进行分子鉴定，这可以为仅通过序列已知的人类基因提供功能提示。
