Genetic polymorphism of beta-lactoglobulin in kenyan small east African goat breed using PCR-RFLP and sequencing

Abstract

Refinement of coherence and economic gains is an essential target in Dairy industry. This can be achieved by increasing economic returns without increasing the size of the herd. Animal selection is the main method for improvement of livestock production around the world. The determination of candidate genes for economic traits holds a promising future as molecular markers for improving productivity in farm animals. Polymorphism in the beta-lactoglobulin gene has been successfully studied in many goat populations of the world. However, this has not been clarified yet in the local Kenyan goat breeds. The objectives of this study were to screen beta-lactoglobulin gene variants and to identify its polymorphism in Small east African goat breed using Polymorphic Chain Reaction and Restriction Fragment Length Polymorphism and sequencing techniques. A total of 60 goats were genotyped, 30 from each region (Samburu and Narok Counties). Genomic DNA was then isolated using Qiagen QiAmp blood mini kit. The amplified product was observed as 426 bp of exon 7 and the restriction digestion with SacII revealed two alleles, namely A and B and three genotypes, (AA, AB and BB) at the β-lactoglobulin gene locus. Allelic frequencies for goats found in Samburu and Narok were 0.233 and 0.133 respectively for A allele; 0.767 and 0.867 for B allele respectively , while genotypic frequencies were 0.1 and 0.0 for AA, 0.267 and 0.267 for AB, and 0.633 and 0.733 for BB respectively. In the pooled data for the small east African goat breed, the allelic frequencies were 0.183 and 0.817 for the A and B allele respectively, while genotypic frequencies were 0.05, 0.267 and 0.683 for the AA, AB and BB respectively. No deviations from the Hardy Weinberg equilibrium were observed. After PCR, a 426 base pairs sequence in exon 7 of 60 goat samples were sequenced and variation analyzed. Two point mutations corresponding to base substitutions were identified. The substitutions of G to A were found at both positions 6705 and 6751 as compared to the Capra hircus sequence (Accession number Z33881.1). Further studies on other beta-lactoglobulin gene regions as well as other milk protein genes are necessary to establish associations of all its variations and the effects of the variants in the indigenous goat breeds.