The adipocyte fatty acid-binding protein locus: characterization and association with intramuscular fat content in pigs

The porcine A-FABP gene (FABP4) was isolated and sequenced to study the rol e of A-FABP in the differentiation of intramuscular fat (IMF) accretion in pigs. The coding sequence of the porcine A-FABP gene is highly conserved ac ross human, mouse, and rat. Moreover, all the functionally important amino acids are conserved. This high similarity extends into the first 270 bp of the 5' upstream region. Within this region, a 56-bp nucleotide sequence was completely identical with the corresponding sequence in the mouse A-FABP g ene, which contains the transcription factor binding sites for C/EBP and AP -1, and is implicated in the differentiation-dependent regulation of A-FABP . The A-FABP gene was assigned to porcine Chromosome (Chr) 4 by a porcine s equence-specific PCR on a cell hybrid panel, fully consistent with comparat ive mapping data with human and mouse. In the first intron of the porcine A -FABP gene, a microsatellite sequence was detected that was polymorphic for all six pig breeds tested. This genetic variation within the A-FABP gene w as associated with differences in IMF content and possibly growth in a Duro c population, whereas no effect on backfat thickness and drip loss of the m eat were detected. A considerable and significant contrast of approximately 1% IMF was observed between certain genotype classes. We conclude that the A-FABP locus is involved in the regulation of intramuscular fat accretion in Duroc pigs.