SNP discovery and association study with milk fat traits in Mediterranean river buffalo Leptin gene

Leptin is a 16 kDa protein highly expressed in the adipose tissue, in pituitary gland, brain and mammary gland. Leptin is responsible for the regulation of body weight and energy homeostasis and is one of the potential biomarker for high animal performances leading to better adaptability and productivity. In dairy and beef cattle, many studies have been reported on associations between Leptin gene (Lep) and traits like meat quality, carcass characteristics, fertility, feed intake, protein yield, energy balance and body weight. Different studies have also reported that this hormone can influence milk’s quality in dairy cattle, sheep and goats. On contrary, there have been limited research regarding association studies between SNPs at this locus and milk traits in buffalo. Lep gene in buffalo consists of three exons and two introns (GenBank:AH013754.2) and it has been mapped on chromosome 8 (BBU8q32). The aim of the present research was to identify and analyse the variability of the Lep locus in Italian Mediterranean river buffalo and to test possible associations with milk fat traits. Individual fresh milk and blood samples were collected from 766 unrelated lactating buffaloes reared in 14 farms of Southern Italy. 306 milk samples were used for fat analysis (fat content, fatty acid composition and fatty acid classes), whereas blood samples were treated for genomic DNA isolation. We sequenced the exon 3 (over 1.8 kb) of 8 buffaloes randomly chosen. Nucleotide alignment showed a synonymous transition GA at the 231th nucleotide of exon 3 that identifies a new allele named A1. The entire panel of DNA samples was genotyped in outsourcing (KBiosciences, Herts, UK). The allele frequency of the common allele (Lep A) was 0.84 (genotype distribution: 547 A/A, 196 A/A1, 23 Lep A1/A1). The statistical analysis, using a mixed linear model, showed no direct effect of Lep g.231G>A genotype on milk fatty acids composition. However, this result does not exclude the existence of an association of this SNP in other buffalo populations for other traits of economic interest