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Rapid development of the canine marker genome map facilitates genome mapping of other Canidae species. In this study we present chromosomal localization of 18 canine-derived cosmid probes containing microsatellites in the arctic fox (Alopex lagopus) and Chinese raccoon dog (Nyctereutes procyonoides procyonoides) genomes by the use of fluorescence in situ hybridization (FISH). The chromosome localizations in the arctic fox are in general agreement with data obtained from comparative genome maps of the dog and the fox. However, our studies showed that the order of the loci on some chromosomes was changed during karyotype evolution. Therefore, we suggest that small intrachromosomal rearrangements took place.

The present study shows new chromosomal localisation of four canine cosmid clones in the Chinese raccoon dog genome by using dual colour FISH. This approach facilitates rapid physical localisation of markers and will improve the determination of their order on chromosomes. The present new assignments increase the number of physically mapped markers in the Chinese raccoon dog to 25.

We have developed a novel method for identifying dog chromosomes and unambiguously mapping specific clones onto canine chromosomes. This method uses a previously established red fox/dog comparative chromosome map to guide the FISH mapping of cloned canine DNA. Mixing metaphase preparations of the red fox and dog enabled a single hybridization to be performed on both species. We used this approach to map the chromosomal locations of twenty-six canine cosmids. Each cosmid contains highly polymorphic microsatellite markers currently used by the DogMap project to compile the canine linkage map. All but two cosmids were successfully assigned to subchromosomal regions on red fox and dog chromosomes. For eight cosmids previously mapped on dog chromosomes, we confirmed and refined the canine chromosomal assignments of seven cosmids and corrected an erroneous assignment regarding cosmid CanBern1. These results demonstrate that the red fox and dog comparative chromosome map can greatly improve the accuracy and efficiency of chromosomal assignments of canine genetic markers by FISH.

Nineteen further polymorphic loci were typed on the DogMap reference panel. Five new linkage groups were identified. Additionally, five markers were added to earlier defined linkage groups. Three of the new linkage groups contain markers mapped earlier to specific dog chromosomes by physical mapping. These results make a further contribution to the canine genome map and provides more linkage groups physically assigned to known chromosomes.