Conserved vertebrate chromosome segments in the large salamander genome.

Urodele amphibians (salamanders) are important models for embryological, physiological, and natural history research and are also a biomedically important group because they are the only vertebrates capable of regenerating entire organ systems. To enhance the utility of salamanders for biomedical research and for understanding genome evolution, genetic linkage analysis was used to identify chromosome segments that are homologous between ambystomatid salamanders and distantly related vertebrate model organisms. A total of 347 loci (AFLPs, RAPDs, and protein-coding loci) were mapped using an interspecific meiotic mapping panel (Ambystoma mexicanum and A. tigrinum tigrinum; family Ambystomatidae). Genome size in Ambystoma was estimated to be 7291 cM, the largest linkage map estimate reported for any organism. However, the relatively large size of the salamander genome did not hinder efforts to map and identify conserved syntenies from a small sample of 24 protein-coding loci. Chromosomal segments that are conserved between fishes and mammals are also conserved in these salamanders. Thus, comparative gene mapping appears to be an efficient strategy for identifying orthologous loci between ambystomatid salamanders and genomically well-characterized vertebrate model organisms.