Association Analysis Between Polymorphism Of Fabp3 And Fabp4 Genes And Milk Fatty Acids Compostion In Dairy Goats

Fatty acid binding proteins(FABPs) play a key role in transporting fatty acid in cell. In mammary gland cell, the mRNA expression of FABP3 and FABP4 is higher during the lactation. The fatty acid binded with FABPs is transported into various organelles for different function. For example, the fatty acid in endoplasmic reticulum could be assembled for systhesising triglyceride; the fatty acid in cell nucleus could regulate the expression of nuclear receptor genes; the fatty acid in mitochondria could be oxidized for energy. Therefore, the genetic changes of these two genes will directly or indirectly influence goat milk production traits, especially milk fatty acid.This study used Xinong Saanen dairy goats mainly to analyze the genetic variation of FABP3 and FABP4 genes. Through the general linear model with collecting milk samples in four months postpartum(DIM30, 60, 90, 120), we expected to screen out the specific SNPs affecting the performance of goat milk significantly. Meanwhile, the factors influencing the fatty acid content would be detected, including day in milk(DIM), parity, test day(TD) and herd. The results are as follows.(1). The present study detected the genetic variations of FABP3 and FABP4 genes in 321 Xinong Saanen dairy goats using DNA pool sequencing and PCR-RFLP, discovering 4 new mutation SNP. One SNP G-986-A was located in exon 1 of FABP3 gene, with the other one SNP C-3064-A located in intron 3 of FABP3 gene. In FABP4 gene, there are two SNPs, one SNP G-3632-A in exon 2 and one SNP A-3716-G in intron 2. One of them was missence mutation SNP C-3064-A(Cys20Tyr) and one was synonymous mutations SNP G-3632-A(Arg60Arg).(2). By analyzing the genetic diversity of FABP3 and FABP4 genes, we obtained the frequency of gene(genotype) for the four mutations, and all the SNP loci in dairy goat belonged to intermediate genetic diversity, by χ2 test according to Hardy – Weinberg equilibrium. Besides, we caculated haplotype variability, extent of linkage disequilibrium(LD) and association analysis in dairy goats. LD analysis showed that SNP G-986-A and C-3064-A loci were in weak linkage(D’<0.7, r2<1/3), while SNP G-3632-A and SNP A-3716-G loci were in strong linkage(D’>0.7, r2>1/3). Haplotype analysis of four SNPs showed the frequency of haplotype(-GA-) in FABP4 gene was highest(59.0%).(3). 37 kinds of fatty acid in goat milk were found out by Gas Chromatography; the most amount fatty acid was stearic acid and the second one was oleic acid. The ratio between saturated fatty acid and unsaturated fatty acid was 2.01. After detecting factors affecting the fatty acid in goat milk, with DIM increasing the amount of unsaturated fatty acid decreased however the amount of polyunsaturated fatty acid increased; with parity growing, the amount of saturated fatty acid increased. Besides, the factors of TD and herd also influence the amount of individual fatty acid significantly.(4). Correlation between genotypes of SNPs in FABP3 and FABP4 genes and milk production traits revealed that, in SNP G-986-A mutation, three genotypes had significant association with milk fat, total solid and long chain fatty acid content and the unsaturated extent of fatty acid in dairy goat(P<0.05); in SNP C-3064-A mutation, three genotypes had no significant association with milk components, but significant association with milk long chain fatty acid content and the unsaturated extent of fatty acid in dairy goat(P<0.05); in SNP G-3632-A mutation, three genotypes were apparently correlated with milk fat, protein, total solid, solid non-fat and long chain fatty acid content and the unsaturated extent of fatty acid in dairy goat(P<0.05); in SNP A-3716-G mutation, three genotypes were not apparently correlated with milk components, but significant association with milk long chain fatty acid content and the unsaturated extent of fatty acid in dairy goat(P<0.05).