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

Area of Science:

• Genetics
• Evolutionary Biology
• Canine Genomics

Background:

• The insulin-like growth factor 1 (IGF1) gene is linked to body size variation in domestic dogs.
• A specific single nucleotide polymorphism (SNP) and SINE element in IGF1 intron 2 are found in small dog breeds but not large ones.

Purpose of the Study:

• Investigate the ancestral variation of the IGF1 gene in grey wolves.
• Determine the origin and evolutionary history of the small dog haplotype.

Main Methods:

• DNA sequencing of IGF1 in grey wolf populations.
• Analysis of single nucleotide polymorphism (SNP) and SINE element distribution.
• Principal Component Analysis (PCA) and phylogenetic analyses.

Main Results:

• The small dog-associated SNP and SINE element were absent in grey wolves and most large dog breeds.
• Grey wolf haplotypes from the Middle East exhibited higher nucleotide diversity.
• The small domestic dog IGF1 haplotype showed closer kinship with Middle Eastern grey wolf haplotypes.

Conclusions:

• The mutation for small body size likely occurred after dog domestication but early in their history.
• The small dog haplotype's close relationship to Middle Eastern wolf haplotypes suggests an ancient origin in that region.
• Molecular data supports archeological findings of early small dog evolution in the Middle East.