Polymorphism Identification in Interleukin-2 Gene in Nigerian Goats

Host defense in vertebrates depend on many secreted regulatory proteins such as CD4⁺ T-cell (Th) cytokines which provide important regulatory and effector functions of T-cells. Among them, interleukin-2 (IL-2) serves as a potent immunomodulator, and plays a unique role in both the activation and maintenance of immune responses and in lymphocyte development. We identified two polymorphic sites (SNPs) in Nigerian goats at positions 128 (T/A) and 413 (T/A), in a 462-bp fragment of caprine IL-2 gene in thirty nine animals. This sequence displayed a 98% nucleotide identity with the referenced Cahi-IL-2 AY603404.1 orthologous sequence in GenBank. Frequencies of the alleles were 0.96 (T) / 0.04 (A) and 0.78 (T) / 0.22(A), with a genotype distribution of 37 TT, 1 TA and 1AA (chi square = 25.34; P<0.05); 25 TT, 11 TA and 3 AA (chi square = 1.01; P>0.05) for SNP at positions 128 and 413, respectively. The neighbor-joining phylogenetic tree (UPGMA) derived from consensus sequences of IL-2 gene revealed that the southern West African Dwarf goats are closer to the northern Red Sokoto goats compared to their Sahel counterparts at this locus. Variation at this locus may prove to be important in possible selection and breeding for genetic resistance to diseases in Nigeria goats, as well as illuminate evolutionary, ecological and conservation questions in Nigerian indigenous goats.

Key words: Cytokines, IL-2, Polymorphisms, Nigerian, Goats