Genetic variation in genes associated with brachycephaly

Sammanfattning: Domestication followed by controlled breeding has generated many dog breeds, displaying high morphological variation. One type of dogs with a dis-tinct morphology is brachycephalic dogs, characterized by a shortened muz-zle, a wide head and widely spaced eyes. The phenotype of brachycephalic dogs has been associated with several health issues, where one of the most obvious is the Brachycephalic Obstructive Airway syndrome (BOAS) which affects the breathing capacity and thermoregulation of the dog. Several stud-ies have aimed to identify the molecular background of the shorter snouts in brachycephalic dogs. So far, mutations in genes such as Bone Morphogenic Protein 3 (BMP3), Fibroblast growth factor 4 (FGF4), SPARC-related mod-ular calcium binding gene 2 (SMOC2) and DISHEVELLED 2 (DVL2) are thought to be associated with the altered skull shape causing canine brachy-cephaly. The aim of this master thesis was to investigate the genetic variation in the genes SMOC2, BMP3, and DVL2 in the Swedish population of four brachycephalic breeds; Boston Terrier, English Bulldog, French Bulldog and Pug. 102 privately owned brachycephalic dogs were genotyped for the muta-tion in the SMOC2 gene, additionally, 45 of these dogs were also genotyped for the mutations in the BMP3 and DVL2 gene. The mutant variant of the SMOC2 gene was fixated in all four breeds. The mutant variant of the BMP3 gene had high allele frequency in all breeds. In Bull type breeds (Boston Terrier, English Bulldog and French Bulldog) the mutant version of the DVL2 gene was fixated, whilst all Pugs were tested wild type for the DVL2 mutation. Low genetic variation will make it more chal-lenging to improve health through genetic selection within the breeds.