AMY2B Gene Copy-Number Variation Studied by Droplet Digital PCR (ddPCR) in Three Canids: Red Fox, Arctic Fox, and Chinese Raccoon Dog

Copy-number variation (CNV) is an important source of genetic variation, and one that played a role in the process of domestication. The adaptation to a new diet is a characteristic feature of dog domestication. We therefore sought genomic signatures of this process. The pancreatic alpha-amylase gene (AMY2B), expressed in the pancreas, exhibits a variable number of copies. It has been shown that the multiplication of this gene is associated with the adaptation of dogs to a starch-rich diet. To date, there has been no information made available on the copy-number variation of AMY2B in canid farm animals. The aim of the present study was to examine the AMY2B copy number in the red fox, the arctic fox, and in the Chinese raccoon dog. Droplet digital PCR (ddPCR) was used to count the gene copies in 152 animals (60 red foxes, 53 arctic foxes, and 39 Chinese raccoon dogs). We found that the majority (91%) of the animals had two copies of this gene. Of the red foxes and Chinese raccoon dogs, only 8% had three copies, while 32% of the arctic foxes had three copies. Our study showed that the multiplication of the AMY2B gene did not occur over several decades of breeding selection, which may reflect the low-starch feeding regime.