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The IGF1 small dog haplotype is derived from Middle Eastern grey wolves.

Gray MM, Sutter NB, Ostrander EA, Wayne RK - BMC Biol. (2010)

Bottom Line: Grey wolf haplotypes from the Middle East have higher nucleotide diversity suggesting an origin there.However, because all small dogs possess these diagnostic mutations, the mutations likely arose early in the history of domestic dogs.Our results show that the small dog haplotype is closely related to those in Middle Eastern wolves and is consistent with an ancient origin of the small dog haplotype there.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA. mgray9@ucla.edu

ABSTRACT

Background: A selective sweep containing the insulin-like growth factor 1 (IGF1) gene is associated with size variation in domestic dogs. Intron 2 of IGF1 contains a SINE element and single nucleotide polymorphism (SNP) found in all small dog breeds that is almost entirely absent from large breeds. In this study, we surveyed a large sample of grey wolf populations to better understand the ancestral pattern of variation at IGF1 with a particular focus on the distribution of the small dog haplotype and its relationship to the origin of the dog.

Results: We present DNA sequence data that confirms the absence of the derived small SNP allele in the intron 2 region of IGF1 in a large sample of grey wolves and further establishes the absence of a small dog associated SINE element in all wild canids and most large dog breeds. Grey wolf haplotypes from the Middle East have higher nucleotide diversity suggesting an origin there. Additionally, PCA and phylogenetic analyses suggests a closer kinship of the small domestic dog IGF1 haplotype with those from Middle Eastern grey wolves.

Conclusions: The absence of both the SINE element and SNP allele in grey wolves suggests that the mutation for small body size post-dates the domestication of dogs. However, because all small dogs possess these diagnostic mutations, the mutations likely arose early in the history of domestic dogs. Our results show that the small dog haplotype is closely related to those in Middle Eastern wolves and is consistent with an ancient origin of the small dog haplotype there. Thus, in concordance with past archeological studies, our molecular analysis is consistent with the early evolution of small size in dogs from the Middle East.See associated opinion by Driscoll and Macdonald: http://jbiol.com/content/9/2/10.

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Principal components analysis of 94 dog-derived single nucleotide polymorphism loci in domestic and wild canids. Principal components one (PC1) is on the X axis and principal components two (PC2) is on the Y axis. The percent variation explained by each axis is also provided.
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Figure 3: Principal components analysis of 94 dog-derived single nucleotide polymorphism loci in domestic and wild canids. Principal components one (PC1) is on the X axis and principal components two (PC2) is on the Y axis. The percent variation explained by each axis is also provided.

Mentions: In order to investigate the evolutionary history of the IGF1 locus and the origin of the haplotypes found in domestic dogs, we performed principal components analysis (PCA) on genotypes from 94 dog-derived SNP markers spanning the IGF1 interval (Figure 1 and Additional File 1: Table S1 and S2; see Methods). Consistent with species level classification, domestic dogs were distinct from grey wolves and coyotes on the first PCA axis (Figure 3). On the second PCA axis, we observed separation between small and large domestic dogs and to a lesser extent between New World and Old World grey wolves. Furthermore, grey wolves of Middle East origin were slightly closer to domestic dogs than other grey wolf populations on the first PCA axis. Several Akita individuals, which is an ancient domestic dog breed [17], were positioned between grey wolves and the main cluster of domestic dogs (Figure 3). Outliers such as large bodied Rottweiler and mastiff dog breeds were observed within the small dog cluster. These breeds were previously found to have unexpected genetic similarity to small dogs in the IGF1 region [16]. The Boston terrier, which is the largest breed in our 'small dog' category, was the breed most associated with the large breed cluster. However, a few individuals from other small breeds were found there as well: cavalier King Charles spaniel, Chihuahua, toy fox terrier, miniature schnauzer, Norwich terrier and Shih Tzu. Moreover, all except the Chihuahua were previously found to exhibit some genetic similarity with large domestic dogs across the IGF1 locus [16]. Phylogenetic analysis of the SNP data defined a domestic dog cluster distinct from grey wolves (Figure S1). Further, the majority of small and large domestic dogs grouped separately from one another. No further resolution within each species was observed.


The IGF1 small dog haplotype is derived from Middle Eastern grey wolves.

Gray MM, Sutter NB, Ostrander EA, Wayne RK - BMC Biol. (2010)

Principal components analysis of 94 dog-derived single nucleotide polymorphism loci in domestic and wild canids. Principal components one (PC1) is on the X axis and principal components two (PC2) is on the Y axis. The percent variation explained by each axis is also provided.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2837629&req=5

Figure 3: Principal components analysis of 94 dog-derived single nucleotide polymorphism loci in domestic and wild canids. Principal components one (PC1) is on the X axis and principal components two (PC2) is on the Y axis. The percent variation explained by each axis is also provided.
Mentions: In order to investigate the evolutionary history of the IGF1 locus and the origin of the haplotypes found in domestic dogs, we performed principal components analysis (PCA) on genotypes from 94 dog-derived SNP markers spanning the IGF1 interval (Figure 1 and Additional File 1: Table S1 and S2; see Methods). Consistent with species level classification, domestic dogs were distinct from grey wolves and coyotes on the first PCA axis (Figure 3). On the second PCA axis, we observed separation between small and large domestic dogs and to a lesser extent between New World and Old World grey wolves. Furthermore, grey wolves of Middle East origin were slightly closer to domestic dogs than other grey wolf populations on the first PCA axis. Several Akita individuals, which is an ancient domestic dog breed [17], were positioned between grey wolves and the main cluster of domestic dogs (Figure 3). Outliers such as large bodied Rottweiler and mastiff dog breeds were observed within the small dog cluster. These breeds were previously found to have unexpected genetic similarity to small dogs in the IGF1 region [16]. The Boston terrier, which is the largest breed in our 'small dog' category, was the breed most associated with the large breed cluster. However, a few individuals from other small breeds were found there as well: cavalier King Charles spaniel, Chihuahua, toy fox terrier, miniature schnauzer, Norwich terrier and Shih Tzu. Moreover, all except the Chihuahua were previously found to exhibit some genetic similarity with large domestic dogs across the IGF1 locus [16]. Phylogenetic analysis of the SNP data defined a domestic dog cluster distinct from grey wolves (Figure S1). Further, the majority of small and large domestic dogs grouped separately from one another. No further resolution within each species was observed.

Bottom Line: Grey wolf haplotypes from the Middle East have higher nucleotide diversity suggesting an origin there.However, because all small dogs possess these diagnostic mutations, the mutations likely arose early in the history of domestic dogs.Our results show that the small dog haplotype is closely related to those in Middle Eastern wolves and is consistent with an ancient origin of the small dog haplotype there.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA. mgray9@ucla.edu

ABSTRACT

Background: A selective sweep containing the insulin-like growth factor 1 (IGF1) gene is associated with size variation in domestic dogs. Intron 2 of IGF1 contains a SINE element and single nucleotide polymorphism (SNP) found in all small dog breeds that is almost entirely absent from large breeds. In this study, we surveyed a large sample of grey wolf populations to better understand the ancestral pattern of variation at IGF1 with a particular focus on the distribution of the small dog haplotype and its relationship to the origin of the dog.

Results: We present DNA sequence data that confirms the absence of the derived small SNP allele in the intron 2 region of IGF1 in a large sample of grey wolves and further establishes the absence of a small dog associated SINE element in all wild canids and most large dog breeds. Grey wolf haplotypes from the Middle East have higher nucleotide diversity suggesting an origin there. Additionally, PCA and phylogenetic analyses suggests a closer kinship of the small domestic dog IGF1 haplotype with those from Middle Eastern grey wolves.

Conclusions: The absence of both the SINE element and SNP allele in grey wolves suggests that the mutation for small body size post-dates the domestication of dogs. However, because all small dogs possess these diagnostic mutations, the mutations likely arose early in the history of domestic dogs. Our results show that the small dog haplotype is closely related to those in Middle Eastern wolves and is consistent with an ancient origin of the small dog haplotype there. Thus, in concordance with past archeological studies, our molecular analysis is consistent with the early evolution of small size in dogs from the Middle East.See associated opinion by Driscoll and Macdonald: http://jbiol.com/content/9/2/10.

Show MeSH
Related in: MedlinePlus