Domestic cats and dogs are both the important companion animals for mankind and model animals for biomedical research. The karyotype of domestic cat is among the most conserved in mammals (including the carnivores), while the karyotype of domestic dog is among the most rearranged. The rapid progress in the canine and feline genome projects has made both genomes the ideal references for comparative genomic studies of carnivores. Cross-species chromosome painting, being accurate, efficient, and suitable for genome-wide comparison, has become the method of choice for comparative cytogenetics, particularly for comparaing distantly related species or species with highly rearranged karyotypes. Comparative chromosome maps, established by chromosome painting, record the history of karyotype changes that have coccured during speciation. The rates, types and directions of chromosomal rearrangements as well as phylogenetic relationships beween species being compared can be inferred by comparative analysis of the distribution patterns of conserved segments in different phylogenetic lineages, and using these characters reconstruct the history of mammalian genome evolution. We have been applying this approach to the study of chromosome evolution of carnivores. A series of comparative chromosome maps among the representative species of major carnivore phylogenetic lineages have been established using complete sets of chromosome-specific painting probes derived from flow-sorted chromosomes of human, domestic cat, stone marten and dog. These maps reveal three levels of genomic reorganiztion, each of which is shared by a group of carnivore species. The feliforms, mustelids, procyonids and red panda have highly conserved karyotypes, the giant panda and ursids have moderately rearranged karyotypes, while the canids have the most highly rearranged karyotypes. The probes from the species with highly conserved karyotypes such as cat and stone marten have been very informative in detecting evolutionary interchromosomal rearrangements, while the probes from dog with highly rearranged genome have been of great importance in tracking intrachromosomal rearrangements that have occurred during the genome evolution of species with conserved karyotypes and have provided further insights into the karyotype evolution of carnivores. Our strategy of comparative chromosome painting based on systematic sampling of representative species permits the tentative reconstruction of the ancestral karyotype and karyotypic phylogeny of camivora. The results also support a close phylogenetic relationship between the red panda and mustelid. These comparative maps help us to understand the genome evolution and phylogenetic relationship among carnivores, and will further facilitate the transfer of gene sequences and mapping data from the human, domestic dog and cat to other carnivore species that are not included in the current priority list of the mapping communities.
修改评论