A Single <i>IGF1</i> Allele Is a Major Determinant of Small Size in Dogs

TLDR

The domestic dog exhibits greater diversity in body size than any other terrestrial vertebrate. The authors used a strategy that exploits the breed structure of dogs to investigate the genetic basis of size. They performed a genome‑wide scan and examined a 15‑megabase interval around a QTL on chromosome 15. They identified a major QTL on chromosome 15, found a selective sweep in IGF1, and discovered a single IGF1 SNP haplotype common to all small breeds and nearly absent from giant breeds, indicating IGF1 as a major determinant of small size.

Abstract

The domestic dog exhibits greater diversity in body size than any other terrestrial vertebrate. We used a strategy that exploits the breed structure of dogs to investigate the genetic basis of size. First, through a genome-wide scan, we identified a major quantitative trait locus (QTL) on chromosome 15 influencing size variation within a single breed. Second, we examined genetic variation in the 15-megabase interval surrounding the QTL in small and giant breeds and found marked evidence for a selective sweep spanning a single gene (IGF1), encoding insulin-like growth factor 1. A single IGF1 single-nucleotide polymorphism haplotype is common to all small breeds and nearly absent from giant breeds, suggesting that the same causal sequence variant is a major contributor to body size in all small dogs.