Nanda I, Benisch P, Fetting D, Haaf T, Schmid M
Department of Human Genetics, University of Würzburg, Würzburg, Germany.
Cytogenet Genome Res. 2011;132(3):165-81. doi: 10.1159/000322358. Epub 2010 Nov 22.
Cross-species chromosome painting can directly visualize syntenies between diverged karyotypes and, thus, increase our knowledge on avian genome evolution. DNA libraries of chicken (Gallus gallus, GGA) macrochromosomes 1 to 10 were hybridized to metaphase spreads of 9 different species from 3 different orders (Anseriformes, Gruiformes and Passeriformes). Depending on the analyzed species, GGA1-10 delineated 11 to 13 syntenic chromosome regions, indicating a high degree of synteny conservation. No exchange between the GGA macrochromosome complement and microchromosomes of the analyzed species was observed. GGA1 and GGA4 were distributed on 2 or 3 chromosomes each in some of the analyzed species, indicating rare evolutionary rearrangements between macrochromosomes. In all 6 analyzed species of Passeriformes, GGA1 was diverged on 2 macrochromosomes, representing a synapomorphic marker for this order. GGA4 was split on 2 chromosomes in most karyotypes, but syntenic to a single chromosome in blackcap (Passeriformes). GGA5/10 and also GGA8/9 associations on chromosomes were found to be important cytogenetic features of the Eurasian nuthatch (Passeriformes) karyotype. Fusion of GGA4 and GGA5 segments and of entire GGA6 and GGA7, respectively, was seen in the 2 analyzed species of Gruiformes. Consistent with the literature, our inter-species chromosome painting demonstrates remarkable conservation of macrochromosomal synteny over 100 million years of avian evolution. The low rate of rearrangements between macrochromosomes and the absence of detectable macrochromosome-microchromosome exchanges suggests a predominant role for rearrangements within the gene-dense microchromosome complement in karyotypic diversification.
跨物种染色体描绘能够直接呈现分化核型之间的同线性，从而增进我们对鸟类基因组进化的了解。鸡（原鸡，GGA）1至10号常染色体的DNA文库与来自3个不同目（雁形目、鹤形目和雀形目）的9个不同物种的中期染色体铺展进行杂交。根据所分析的物种不同，GGA1 - 10划定了11至13个同线染色体区域，表明同线性保守程度较高。在所分析的物种中，未观察到GGA常染色体组与微染色体之间的交换。在一些所分析的物种中，GGA1和GGA4分别分布在2条或3条染色体上，表明常染色体之间存在罕见的进化重排。在所有6种所分析的雀形目物种中，GGA1在2条常染色体上发生了分化，这是该目的一个共衍征标记。在大多数核型中，GGA4在2条染色体上分裂，但在黑头莺（雀形目）中与一条单一染色体同线。发现GGA5/10以及GGA8/9在染色体上的关联是欧亚坚果雀（雀形目）核型的重要细胞遗传学特征。在2种所分析的鹤形目物种中，分别观察到了GGA4和GGA5片段的融合以及整个GGA6和GGA7的融合。与文献一致，我们的种间染色体描绘表明，在超过1亿年的鸟类进化过程中，常染色体同线性具有显著的保守性。常染色体之间的重排率较低，且未检测到常染色体 - 微染色体交换，这表明在核型多样化过程中，基因密集的微染色体组内的重排起主要作用。
