DNA Characterization and Polymorphism of KISS1 Gene in Egyptian Small Ruminant Breeds
Genetic information especially of the Quantitative Trait Loci (QTL) which affect different performance traits is considered one of the most effective tools in the breeding programs of livestock. Several genes were reported as candidate genes that effect litter size performance and one of these genes is the KISS1 which is considered as a regulator of puberty onset. The polymorphisms of KISS1 gene have some relationships with high prolific and sexual precocity. The objective of this study was the detection of the restriction fragment length polymorphism (RFLP) and single nucleotide polymorphisms (SNPs) of KISS1 gene in six major Egyptian small ruminant breeds. The primers used in this study flanked a 377 bp fragment from intron 1 of KISS1 gene in sheep and goat. These PCR amplified fragments were digested with XmnI endonuclease. According to the presence or absence of the restriction site (GAANN^NNTTC) at position 121^122, we genotyped the 122 tested animals as AT (54.92%) and TT (45.08) with the absence of AA genotype. The overall frequencies of alleles A and T were 27.46 and 72.54%, respectively. The sequence analysis of purified PCR products representing these two detected genotypes declared the presence of a SNP (T→A) at position 125 in the amplified fragment which is responsible for the elimination of the restriction site and consequently the presence of two different alleles T and A. The nucleotide sequences of sheep KISS1 alleles T and A as well as goat KISS1 alleles T and A were submitted to GenBank database and have accession numbers: KP835797, KP835798, KP835799 and KP835800, respectively. It is concluded that small ruminant breeds have high frequency of KISS1 allele T which was associated with greater litter size. We recommend to increase this allele in Egyptian small ruminant breeds and also to select the animals which possess TT genotypes of KISS1 gene and enter them in breeding programs of Egyptian small ruminants to increase their fecundity traits.
Keywords: Sheep, Goat, KISS1, Polymerase Chain Reaction (PCR), Restriction Fragment Length Polymorphism (RFLP), Single Nucleotide Polymorphisms (SNPs)