Supplementary Material for: Two Candidate Genes <i>(FTO</i> and <i>INSIG2)</i> for Fat Accumulation in Four Canids: Chromosome Mapping, Gene Polymorphisms and Association Studies of Body and Skin Weight of Red Foxes

Fat accumulation is a polygenic trait which has a significant impact on human health and animal production. Obesity is also an increasingly serious problem in dog breeding. The <i>FTO</i> and <i>INSIG2 </i>are considered as candidate genes associated with predisposition for human obesity. In this report we present a comparative genomic analysis of these 2 genes in 4 species belonging to the family Canidae – the dog and 3 species which are kept in captivity for fur production, i.e. red fox, arctic fox and Chinese raccoon dog. We cytogenetically mapped these 2 loci by FISH and compared the entire coding sequence of <i>INSIG2</i> and a fragment of the coding sequence of <i>FTO. </i>The <i>FTO</i> gene was assigned to the following chromosomes: CFA2q25 (dog), VVU2q21 (red fox), ALA8q25 (arctic fox) and NPP10q24–25 (Chinese raccoon dog), while the <i>INSIG2</i> was mapped to CFA19q17, VVU5p14, ALA24q15 and NPP9q22, respectively. Altogether, 29 SNPs were identified (16 in <i>INSIG2</i> and 13 in <i>FTO</i>) and among them 2 were missense substitutions in the dog (23C/T, Thr>Met in the <i>FTO </i>gene and 40C/A, Arg>Ser in <i>INSIG2</i>). The distribution of these 2 SNPs was studied in 14 dog breeds. Two synonymous SNPs, one in the <i>FTO</i> gene (–28T>C in the 5′-flanking region) and one in the <i>INSIG2</i> (10175C>T in intron 2), were used for the association studies in red foxes (n = 390) and suggestive evidence was observed for their association with body weight (<i>FTO</i>, p < 0.08) and weight of raw skin (<i>INSIG2</i>, p < 0.05). These associations indicate that both genes are potential candidates for growth or adipose tissue accumulation in canids. We also suggest that the 2 missense substitutions found in dogs should be studied in terms of genetic predisposition to obesity.