Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia.
Genome Biol Evol. 2021 Apr 5;13(4). doi: 10.1093/gbe/evab044.
A manually curated set of ohnolog families has been assembled, for seven species of bony vertebrates, that includes 255 four-member families and 631 three-member families, encompassing over 2,900 ohnologs. Across species, the patterns of chromosomes upon which the ohnologs reside fall into 17 distinct categories. These 17 paralogons reflect the 17 ancestral chromosomes that existed in our chordate ancestor immediately prior to the two rounds of whole-genome duplication (2R-WGD) that occurred around 600 Ma. Within each paralogon, it has now been possible to assign those pairs of ohnologs that diverged from each other at the first round of duplication, through analysis of the molecular phylogeny of four-member families. Comparison with another recent analysis has identified four apparently incorrect assignments of pairings following 2R, along with several omissions, in that study. By comparison of the patterns between paralogons, it has also been possible to identify nine chromosomal fusions that occurred between 1R and 2R, and three chromosomal fusions that occurred after 2R, that generated an ancestral bony-vertebrate karyotype comprising 47 chromosomes. At least 27 of those ancestral bony-vertebrate chromosomes can, in some extant species, be shown not to have undergone any fusion or fission events. Such chromosomes are here termed "archeochromosomes," and have each survived essentially unchanged in their content of genes for some 400 Myr. Their utility lies in their potential for tracking the various fusion and fission events that have occurred in different lineages throughout the expansion of bony vertebrates.
已人工整理了一组骨鱼脊椎动物的同源基因家族，包括 7 种物种的 255 个四联体家族和 631 个三联体家族，涵盖了超过 2900 个同源基因。在不同物种中，同源基因所在的染色体模式分为 17 个不同类别。这 17 个同源基因簇反映了我们的脊索动物祖先在发生两轮全基因组复制（2R-WGD）之前存在的 17 条祖先染色体，两轮全基因组复制大约发生在 6 亿年前。在每个同源基因簇中，通过分析四联体家族的分子系统发育，现在已经可以确定那些在第一轮复制中彼此分化的同源基因对。与另一项最近的分析相比，在该研究中发现了四个明显不正确的 2R 后配对分配，以及几个遗漏。通过比较同源基因簇之间的模式，还可以确定在 1R 和 2R 之间发生了 9 次染色体融合，以及在 2R 之后发生了 3 次染色体融合，产生了一个由 47 条染色体组成的祖先骨鱼染色体组型。至少有 27 条祖先骨鱼染色体可以在一些现存物种中显示没有经历过任何融合或裂变事件。这些染色体被称为“原始染色体”，它们的基因内容在大约 4 亿年的时间里基本保持不变。它们的用途在于它们可以追踪在骨鱼脊椎动物的扩张过程中不同谱系中发生的各种融合和裂变事件。
