Nash W G, Menninger J C, Wienberg J, Padilla-Nash H M, O'Brien S J
H & W Cytogenetic Services, Inc., Lovettsville, VA, USA.
Cytogenet Cell Genet. 2001;95(3-4):210-24. doi: 10.1159/000059348.
Canidae species fall into two categories with respect to their chromosome composition: those with high numbered largely acrocentric karyotypes and others with a low numbered principally metacentric karyotype. Those species with low numbered metacentric karyotypes are derived from multiple independent fusions of chromosome segments found as acrocentric chromosomes in the high numbered species. Extensive chromosome homology is apparent among acrocentric chromosome arms within Canidae species; however, little chromosome arm homology exists between Canidae species and those from other Carnivore families. Here we use Zoo-FISH (fluorescent in situ hybridization, also called chromosomal painting) probes from flow-sorted chromosomes of the Japanese raccoon dog (Nyctereutes procyonoides) to examine two phylogenetically divergent canids, the arctic fox (Alopex lagopus) and the crab-eating fox (Cerdocyon thous). The results affirm intra-canid chromosome homologies, also implicated by G-banding. In addition, painting probes from domestic cat (Felis catus), representative of the ancestral carnivore karyotype (ACK), and giant panda (Ailuropoda melanoleuca) were used to define primitive homologous segments apparent between canids and other carnivore families. Canid chromosomes seem unique among carnivores in that many canid chromosome arms are mosaics of two to four homology segments of the ACK chromosome arms. The mosaic pattern apparently preceded the divergence of modern canid species since conserved homology segments among different canid species are common, even though those segments are rearranged relative to the ancestral carnivore genome arrangement. The results indicate an ancestral episode of extensive centric fission leading to an ancestral canid genome organization that was subsequently reorganized by multiple chromosome fusion events in some but not all Canidae lineages.
就染色体组成而言，犬科物种可分为两类：一类具有高编号的主要为近端着丝粒核型，另一类具有低编号的主要为中着丝粒核型。那些具有低编号中着丝粒核型的物种源自高编号物种中作为近端着丝粒染色体存在的染色体片段的多次独立融合。犬科物种内近端着丝粒染色体臂之间存在广泛的染色体同源性；然而，犬科物种与其他食肉动物科的染色体臂同源性很少。在这里，我们使用来自日本貉（Nyctereutes procyonoides）流式分选染色体的动物园荧光原位杂交（FISH，也称为染色体涂染）探针来检测两种系统发育上不同的犬科动物，北极狐（Alopex lagopus）和食蟹狐（Cerdocyon thous）。结果证实了犬科内部的染色体同源性，G带分析也暗示了这一点。此外，还使用了代表原始食肉动物核型（ACK）的家猫（Felis catus）和大熊猫（Ailuropoda melanoleuca）的涂染探针来确定犬科与其他食肉动物科之间明显的原始同源片段。犬科染色体在食肉动物中似乎很独特，因为许多犬科染色体臂是ACK染色体臂的两到四个同源片段的镶嵌体。这种镶嵌模式显然在现代犬科物种分化之前就已存在，因为不同犬科物种之间保守的同源片段很常见，尽管这些片段相对于原始食肉动物基因组排列发生了重排。结果表明，曾发生过一次广泛的着丝粒裂变事件，导致了一个原始犬科基因组组织，随后在一些但并非所有犬科谱系中通过多次染色体融合事件进行了重组。
