Polymorphism analysis of AMY1, AMY2, SLC5A1, SLC2A2 and SLC2A5 genes in Italian horse breeds

Abstract

The dietary demand of modern competition horse relies on high-cereal feeding daily interspersed by limited forage and it is frequently characterized by marked changes in carbohydrate fractions, above all starch, compared to natural grazing conditions. These dietary variations influence digestion, metabolism, and increase the risk for colic and laminitis, both main causes of equine mortality. Aim of this work has been to analyze the polymorphism of genes related to digestion and absorption of complex carbohydrates, particularly starch, to make a comparison between different cosmopolite and Italian native horse breeds, characterized by marked differences in feeding and management conditions. The analyzed genes were: salivary and pancreatic alpha-amylases (AMY1 and AMY2, respectively), solute carrier family 2, facilitated glucose transporter member 2 (SLC2A2) and member 5 (SLC2A5) and sodium/glucose cotransporter 1 (SLC5A1), code for GLUT2, GLUT5 and SGLT1 enzymes, respectively, main routes for the transport of dietary sugars from the lumen of the intestine into enterocytes. Horses belonging to three cosmopolite breeds, Throughbred, Purebred Arabian and Friesian, and three southern Italian native breeds, Sanfratellano, Indigeno Siciliano and Murgese, 2 DNA samples per breed, were pooled. SNP detection was performed by sequencing one DNA pool per breed. A total of 13 novel single nucleotide polymorphisms were found. Six SNPs are located in AMY1 gene and 3 are in exons, of which 1 is non-synonymous. A non-synonymous SNP was also identified in exon 1 of AMY2 gene. No SNPs were found in the SLC2A2 gene region analyzed, while 4 SNPs were characterized in 3\u2019UTR of SLC2A5 gene. Finally, 4 SNPs were found in SLC5A1 gene, all located in intron 3. Three out of the SNPs found in AMY1 and AMY2 genes were genotyped in 121 horses belonging to the analyzed breeds, with the addition of Haflinger and Sella Italiano breeds samples. The results of the SNP genotyping are presented