GENETIC VARIATION OF LEPTIN GENE INTHREE NIGERIAN CATTLE BREEDS

摘要

Leptin, a 16 kDa polypeptide hormone is synthesized predominantly in the adipose tissue and affects a number of processes in the body.This study evaluated the genetic variation in the leptin gene in three Nigerian cattle breeds (White Fulani, Kuri andN'Dama).A total of 45 blood samples were collected from different farms across Nigeria from which DNA was extracted and amplified.The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to screen for DNA polymorphisms of the leptin gene in the DNA samples. One region of the leptin gene was amplified, a 620 bp fragment comprising part of intron I and exon 2.The amplified products were digested with Mspl and Hindlll restriction enzymes and heterozygosity estimates, genetic differentiation (F-statistics), genetic distances and phylogenic relationships among the cattle breeds were determined. Analysis using Mspl showed the allelic frequencies in each breed indicated that allele B in White Fulani, Kuri and N'Dama cattle with 50%, 47%, and 50% values respectively, was the most frequent.The Kuri breed had the highest observed and expected heterozygosities in the leptin locus, 56.7% and 35.2% respectively, while the White Fulani had the lowest observed homozygosity and expected heterozygosity at the leptin locus; 43.3% and 32.3% respectively. The Shannon's information index at the leptin locus among breeds are 46.9%, 50.8%, and 52.2% among White Fulani, Kuri and N'Dama cattle breeds respectively. Results on the inbreeding coefficient (FIS) revealed outbreeding (-0.152) with high genetic differentiation (FST) (0.573) indicating a high gene flow (Nm) rate (0.230) among breeds. The phylogenetic relationship among the three cattle breeds shows a distinct clusteringfor the White Fulani as a group, while the Kuri and N'Dama formed the second cluster.The divergence of the White Fulani cattle breed from the other two breeds is attributable to its zebu nature while the Kuri and Ndama clustering suggests their taurine descent.