Variations On Adipocyte Fatty-acid Binding Protein(A-FABP) Gene In Sheep Of China

The adipocyte fatty-acid binding protein(A-FABP) belongs to the fatty-acid binding protein family(FABPs), and it is believed that the A-FABP protein participates in the process of fatty acid metabolism by combining and transporting long-chain fatty acid. Based on the complete sequence of ovine A-FABP gene in Ensemble database, the A-FABP gene was sequenced and analyzed to reveal the characteristics of variation and haplotype in 20 samples collected from 7 breeds. These results showed that the sequence(6474 bp) of the A-FABP gene was obtained by the PCR process. The ratio of four bases(A, T, G and C) is 31.48%, 33.02%, 17.21% and 18.29% respectively, and the average content of A+T and G+C is 64.50% and 35.50% respectively. Forty eight variation sites and two microsatellite locuss for M1((TG)n)and M2((TA)n)were found, the percentage of single variation site, two variation sites and three variation sites was 28.85%, 40.4% and 0.02% respectively. Four variation types(transition, transversion, insertion and deletion) were observed, and their ratio was 45.83%、31.25%、2.08% and 20.83% respectively. Nineteen haplotypes were found, and the haplotype diversity was 0.995. The NJ tree constructed by nineteen haplotypes developed two main clades, which indicated that 19 haplotypes were initially derived from two main haplotypes.The genetic polymorphism and variability of exon2-intron2 and exon3-intron3 of A-FABP gene in four sheep groups were systematically analyzed using PCR-single stranded conformational polymorphism(PCR-SSCP). The results displayed that there were 4 alleles(A, B, C, D) detected, combined six genotypes(AA, AC, AD, BB, BC, CC)in exon2-intron2. Allele A was the predominant allele. The advantage genotype was different in different groups. The advantages genotype of Tan Sheep group, Tibetan Sheep group and Qinghai fine wool sheep group respectively are BC, AA and AC.There were 4 mutation site(61bp A�'G, 390 bp C�'T, 448 bp C�'T, 258 bp T�'C)were detected in four groups, combined AA, BB, AB, AC and CD 5 genotypes were controlled by A, B, C, D alleles in exon3-intron3. Allele A was the predominant allele.The genotype and allele distribution is not balanced between the groups. Allele D varated in 61 bp A �' G caused amino acid mutations in exon3-intron3. Other mutations occured in the region of the introns, so no amino acid mutation was happened.There were a total of eight mutations found in A-FABPA coding region(exon2-intron2 and exon3-intron3), one site was base deletion and accounting for 12.5% of the mutations; there were six base transitions, accounting for 75% of the mutations; only one site occurred base transversion, accounting for 12.5% of the mutations. In exon2-intron2, except Tibetan Sheep for moderate polymorphism(0. 25﹤PIC﹤0.5), Gansu Alpine Merino, Tan Sheep and Qinghai fine wool sheepare highly polymorphic(0.5﹤PIC). In exon3-intron3, except Gansu Alpine Merino for highly polymorphism(0.5﹤PIC), Gansu Alpine Merino, Tan Sheep and Qinghai fine wool sheep were moderate polymorphic(0.25﹤PIC﹤0.5). The genetic polymorphism information in exon2-intron2 and exon3-intron3 showed that, the numerical of He and Ne were the biggest in Gansu Alpine Merino group in two areas. Chi square test results showed that, they all deviated from the Hardy-Weinberg(P﹤0.05) in exon2-intron2 and exon3-intron3 regions of four group.To sum up, the sheep A-FABP gene is highly polymorphic, is very rich in genetic diversity. The study of its polymorphism can promote the research of evolution of the A-FABP gene and accumulate material for the reseach of candidate genes of growth and fat traits in sheep.