In:
Science, American Association for the Advancement of Science (AAAS), Vol. 380, No. 6643 ( 2023-04-28)
Abstract:
It has been almost 100 years since the sled dog Balto helped save the community of Nome, Alaska, from a diphtheria outbreak. Today, Balto symbolizes the indomitable spirit of the sled dog. He is immortalized in statue and film, and is physically preserved and on display at the Cleveland Museum of Natural History. Balto represents a dog population that was reputed to tolerate harsh conditions at a time when northern communities were reliant on sled dogs. Investigating Balto’s genome sequence using technologies for sequencing degraded DNA offers a new perspective on this historic population. RATIONALE Analyzing high-coverage (40.4-fold) DNA sequencing data from Balto through comparison with large genomic data resources offers an opportunity to investigate genetic diversity and genome function. We leveraged the genome sequence data from 682 dogs, including both working sled dogs and dog breeds, as well as evolutionary constraint scores from the Zoonomia alignment of 240 mammals, to reconstruct Balto’s phenotype and investigate his ancestry and what might distinguish him from modern dogs. RESULTS Balto shares just part of his diverse ancestry with the eponymous Siberian husky breed and was more genetically diverse than both modern breeds and working sled dogs. Both Balto and working sled dogs had a lower burden of rare, potentially damaging variation than modern breeds and fewer potentially damaging variants, suggesting that they represent genetically healthier populations. We inferred Balto’s appearance on the basis of genomic variants known to shape physical characteristics in dogs today. We found that Balto had a combination of coat features atypical for modern sled dog breeds and a slightly smaller stature, inferences that are confirmed by comparison to historical photographs. Balto’s ability to digest starch was enhanced compared to wolves and Greenland sled dogs but reduced compared to modern breeds. He carried a compendium of derived homozygous coding variants at constrained positions in genes connected to bone and skin development, which may have conferred a functional advantage. CONCLUSION Balto belonged to a population of small, fast, and fit sled dogs imported from Siberia. By sequencing his genome from his taxidermied remains and analyzing these data in the context of large comparative and canine datasets, we show that Balto and his working sled dog contemporaries were more genetically diverse than modern breeds and may have carried variants that helped them survive the harsh conditions of 1920s Alaska. Although the era of Balto and his contemporaries has passed, comparative genomics, supported by a growing collection of modern and past genomes, can provide insights into the selective pressures that shaped them. Balto, famed 20th-century Alaskan sled dog, shares common ancestry with modern Asian and Arctic canine lineages. In an unsupervised admixture analysis, Balto’s ancestry, representing 20th-century Alaskan sled dogs, is assigned predominantly to four Arctic lineage dog populations. He had no discernable wolf ancestry. The Alaskan sled dogs (a working population) did not fall into a distinct ancestry cluster but shared about a third of their ancestry with Balto in the supervised admixture analysis. Balto and working sled dogs carried fewer constrained and missense rare variants than modern dog breeds. IMAGE CREDIT: K. MORRILL
Type of Medium:
Online Resource
ISSN:
0036-8075
,
1095-9203
DOI:
10.1126/science.abn5887
Language:
English
Publisher:
American Association for the Advancement of Science (AAAS)
Publication Date:
2023
detail.hit.zdb_id:
128410-1
detail.hit.zdb_id:
2066996-3
detail.hit.zdb_id:
2060783-0
SSG:
11
