Sequence characterization, tissue-specific expression and polymorphism of the porcine intestinal-type fatty acid binding protein gene

The intestinal fatty-acid-binding protein (IFABP) shows binding specificity for long-chain fatty acids and is proposed to be involved in the uptake of dietary fatty acids and their intracellular transport. In this study, the full-length cDNA of porcine I-FABP gene was obtained by the rapid amplification of cDNA ends (RACE). The nucleotide sequence and the predicted protein sequence share high sequence identity with its mammalian counterparts. Northern hybridization and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed that porcine I-FABP is expressed in all 12 tissues studied (heart, brain, kidney, skeletal muscle, testis, liver, skin, small intestine, fat, stomach, lymph and pituitary), but a transcript of approximate 620 bp is more abundant in small intestine than in other tissues. The full-length genomic DNA of the porcine I-FABP gene was amplified by PCR. The coding region of the pig IFABP gene is organized in four exons and spans an approximate 3.5-kb genomic region. Comparative sequencing of four pig breeds revealed a single nucleotide polymorphism (SNP) within exon 1 of which an A→G substitution at codon 21 changes a codon for lysine into a codon for arginine. The distribution of allele and genotype frequencies differed significantly between indigenous Chinese Zang, Dahe and Yanan breeds (higher frequencies of A and AA) and Western Large White breed (higher frequencies of G and GG, P < 0.01). The association analysis using five pig populations suggested that A21G polymorphism was associated with intramuscular fat content, indicating that the I-FABP gene A21G SNP can be a potential molecular marker for intramuscular fat content. Key words: Association analysis, cloning, gene expression, I-FABP gene, polymorphism, porcine