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We reconstruct the phenotype of Balto, the heroic sled dog renowned for transporting diphtheria antitoxin to Nome, Alaska, in 1925, using evolutionary constraint estimates from the Zoonomia alignment of 240 mammals and 682 genomes from dogs and wolves of the 21st century. Balto shares just part of his diverse ancestry with the eponymous Siberian husky breed. Balto's genotype predicts a combination of coat features atypical for modern sled dog breeds, and a slightly smaller stature. He had enhanced starch digestion compared with Greenland sled dogs and a compendium of derived homozygous coding variants at constrained positions in genes connected to bone and skin development. We propose that Balto's population of origin, which was less inbred and genetically healthier than that of modern breeds, was adapted to the extreme environment of 1920s Alaska.

We reconstruct the phenotype of Balto, the heroic sled dog renowned for transporting diphtheria antitoxin to Nome, Alaska, in 1925, using evolutionary constraint estimates from the Zoonomia alignment of 240 mammals and 682 genomes from dogs and wolves of the 21st century. Balto shares just part of his diverse ancestry with the eponymous Siberian husky breed. Balto's genotype predicts a combination of coat features atypical for modern sled dog breeds, and a slightly smaller stature. He had enhanced starch digestion compared with Greenland sled dogs and a compendium of derived homozygous coding variants at constrained positions in genes connected to bone and skin development. We propose that Balto's population of origin, which was less inbred and genetically healthier than that of modern breeds, was adapted to the extreme environment of 1920s Alaska.

[INTRODUCTION] 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.

Global warming is expected to result in larger temperature fluctuations by which heat stress may become an important stressor for animals, affecting health and productivity. Animals can cope with and adapt to heat stress by changing their physiology. To investigate general physiological reactions to heat stress in muscle and heart tissues of chickens we combined results from three independent experiments. Two experiments studied the transcriptome profiles of heart and muscle tissues of mature chickens using heat stress adapted and nonadapted chickens. One experiment studied the epigenome changes of heat stress during chicken egg incubation. In all three datasets epigenome changes were important biological response mechanisms, which may underlie genome-wide regulation of the affected biological mechanisms. Pre and postnatal heat stress reaction showed changed expression of genes related to metabolic rate, energy, and protein metabolism. Furthermore, tissue integrity may be affected due to changed cell−cell contacts, vascularization, and growth reduction.

In the original article, there was a mistake in Supplementary Table 1 and Supplementary Table 2. The expression values given for PDK4 in Supplementary Table 1, ALL_M, CLL_M, AHL_M, CHL_M contrasts were -3.90808, 2.10011, -4.12057, and -4.12057 the correct values are -4.1009, 2.07292, -4.63904, and 3.05659 same value should appear at the “Max_expression_level” column in HL_node_table in Supplementary Table 2. Similarly the expression values of MT4 given in Supplementary Table 1 for ALL_H, CLL_H, AHL_H, and CHL_H are -1.20147, 1.485881, -1.19557, and 1.0025, the correct values are -3.1675, -1.82983, -1.35669, and -1.84142. To reflect this change, columns “Max_expression_level,” “Max_Tissue,” and “Up/Down” on Supplementary Table 2, “LL_node_table” tab is corrected. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.

Temperature stress impacts both welfare and productivity of livestock. Global warming is expected to increase the impact, especially in tropical areas. We investigated the biological mechanisms regulated by temperature stress due to the circadian temperature cycle in temperature adapted and non-adapted chicken under tropical conditions. We studied transcriptome profiles of heart, breast muscle, and spleen tissues of Ethiopian lowland chicken adapted to high circadian temperatures and non-adapted Ethiopian highland chicken under lowland conditions at three points during the day: morning, noon, and evening. Functional annotations and network analyses of genes differentially expressed among the time points of the day indicate major differences in the reactions of the tissues to increasing and decreasing temperatures, and also the two chickens lines differ. However, epigenetic changes of chromatin methylation and histone (de)acetylation seemed to be central regulatory mechanisms in all tissues in both chicken lines. Finally, all tissues showed differentially expressed genes between morning and evening times indicating biological mechanisms that need to change during the night to reach morning levels again the next day.

Heat stress (HS) negatively affects chicken performance. Agricultural expansion will happen in regions that experience high ambient temperatures, where fast-growing commercial chickens are vulnerable. Indigenous chickens of such regions, due to generations of exposure to environmental challenges, might have higher thermal tolerance. In this study, two indigenous chicken ecotypes, from the hot and humid Mombasa (lowland) and the colder Naivasha (highland) regions, were used to investigate the effects of acute (5 h, 35°C) and chronic (3 days of 35°C for 8 h/day) HS on the cardiac and skeletal muscle, through RNA sequencing. The rectal temperature gain and the number of differentially expressed genes (DEGs) [False Discovery Rate (FDR) < 0.05] were two times higher in the acute stage than in the chronic stage in both ecotypes, suggesting that cyclic exposure to HS can lead to adaptation. A tissue- and stage-specific difference in response to HS was observed, with peroxisome proliferator-activated-receptor (PPAR) signaling and mitogen-activate protein kinase (MAPK) signaling pathways, enriched in heart and skeletal muscle, respectively, and the p53 pathway enriched only in the acute stage in both tissues. The acute and chronic stage DEGs were integrated by a region-specific gene coexpression network (GCN), and genes with the highest number of connections (hub genes) were identified. The hub genes in the lowland network were CCNB2, Crb2, CHST9, SESN1, and NR4A3, while COMMD4, TTC32, H1F0, ACYP1, and RPS28 were the hub genes in the highland network. Pathway analysis of genes in the GCN showed that p53 and PPAR signaling pathways were enriched in both low and highland networks, while MAPK signaling and protein processing in endoplasmic reticulum were enriched only in the gene network of highland chickens. This shows that to dissipate the accumulated heat, to reduce heat induced apoptosis, and to promote DNA damage repair, the ecotypes activated or suppressed different genes