Cloning, expression and investigation for polymorphisms of canine peroxisome proliferator-activated receptors

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors implicated in lipid metabolism. In this study, the full-length cDNA of canine PPARbeta and gamma were sequenced, and expression of PPARs was evaluated in normal tissues and primary cultures of adipocytes in dogs, followed by investigations for polymorphisms of canine PPARgamma. Comparison of the deduced amino acid sequences of canine PPARbeta and gamma cDNA with that of human PPARbeta and gamma cDNA revealed 95.9% and 98.2% identity, respectively. PPARbeta expression was ubiquitous and high PPARgamma expression was detected in the subcutaneous and omental adipose tissues, spleen and large intestine. Canine PPARgamma mRNA expression in cultured adipocytes began to increase from 4 days after induction of differentiation, and increased nearly ninefold within 10 days after induction of differentiation. Although expression level of PPARalpha was low in the cultured adipocytes, it slightly increased within 10 days. In contrast, expression of PPARbeta showed only small variations during adipocyte differentiation, though expression levels were relatively high. These results suggest that PPARgamma may play an important role in adipocyte differentiation in dogs. Investigations for polymorphisms of PPARgamma revealed a silent polymorphism, C1362T, in 3 of 92 dogs.