“Canine Transmissible Venereal Tumor Genome Reveals Ancient Introgression from Coyotes to Arctic Sled Dogs”, 2018-06-19 (; similar):
Canine transmissible venereal tumor (CTVT), the oldest known somatic cell line, is a living fossil, originating from cancer cells transmitted from a host to other canids during the mating process. Clonal origin analyses hints that the original dog infected with CTVT (CTVT founder) came from an ancient sled dog or wolf population. However, the genetic composition of the CTVT founder is still not clear.
In order to explore this issue, we applied whole genome sequencing (WGS) to two CTVT samples, their corresponding hosts, and 24 additional canids (Supplementary Note). Combined with published WGS data of two CTVT samples and high quality canine WGS data, we constructed a data set containing WGS data of four CTVT samples a 169-individual reference panel composed of worldwide gray wolves (Canis lupus), dogs (Canis lupus familiaris), coyotes (Canis latrans) and golden jackals (Canis aureus) (Supplementary Note, Table S1).
…Our results reveal that the CTVT founder was more closely related to present-day arctic sled dogs than to any other populations (Figure S6–8), in accordance with very recent results. However, ADMIXTURE analysis showed that the CTVT founder also possessed an ancestral component found predominantly in non-dog populations, a result that we do not observe for any arctic sled dog (Supplementary Note, Figure 1A). Moreover, the CTVT founder did not cluster tightly with arctic sled dogs in the PCA analysis (Figure S7). These results imply that the CTVT founder belonged to a previously unknown arctic dog population that is not represented in the reference panel…
In conclusion, our detailed analyses reveal that the CTVT founder came from an arctic sled dog population that possessed introgression from a population related to coyotes, a result that was not known in previous studies. Considering the habitat of coyotes in North America, we propose two hypotheses: (1) The CTVT founder lived in the arctic region of North America. (2) The CTVT founder lived in the arctic region of the Far East, where arctic dogs possessing the introgressed segments migrated through the Bering Strait in an unknown period. Hence, an ancient story of canine admixture is hidden in the genome of a living fossil, the CTVT. To further test our hypotheses of ancient admixture and to better understand the detailed evolutionary history of dogs from the arctic region and Americas, it is crucial to acquire ancient samples in these regions in future work.