Apolipoprotein E4 Prevalence in Different Canine Breeds

Abstract

Three common isoforms of apolipoprotein E (APOE) are found in most populations: E2, E3, and E4, the Ε4 isoform has been proven to be associated with Alzheimer’s disease (AD) and coronary heart disease (CHD). In human, attributable risk due to APOE4 varies by region and by race/ethnicity. To gain a better understanding of APOE genetic polymorphism in canines, we aimed to explore the prevalence of apolipoprotein E isoform distribution in five different pure breeds (Thai Ridgeback, Golden Retriever, Labrador Retriever, Bulldog, Shih Tzu) using APOE gene sequencing analysis. Our results showed a very high homology of apolipoprotein E sequences in the examined canines, including human APOE3 and human APOE4, ranging from 71.76-100 and 78.23-100% identity and similarity, respectively. All investigated canine breeds could be identified as APOE4 carriers due to the presence of arginine at the positions 112 and 158, which correspond to APOE4 of human. This indicates that APOE polymorphism was not present in the genome of all examined canine breeds. It is possible that the finding of canine apolipoprotein E4 may be important in predicting an increased risk of pathophysiological development of neurodegenerative diseases and coronary heart disease. Our reconstructed phylogenetic tree showed two well-defined clusters based on the amino acid sequence of apolipoprotein E, including canine and human group. Further studies should explore if these different clusters are associated with diseases.