The effect of adipocyte and heart fatty acid-binding protein genes on intramuscular fat and backfat content in Meishan crossbred pigs.

Effects of genetic variation in porcine adipocyte and heart fatty acid-binding protein genes, A-FABP and H-FABP, respectively, on intramuscular fat (IMF) content and backfat thickness (BFT) were examined in F2 crossbreds of Meishan and Western pigs. The involvement of each FABP gene in IMF accretion was studied to confirm previous results for Duroc pigs. The F2 crossbred pigs were genotyped for various markers including microsatellite sequences situated within both FABP genes. Linkage analysis assigned the A-FABP and H-FABP genes to marker intervals S0001-S0217 (20 cM) on SSC4 and Sw316-S0003 (16.6 cM) on SSC6, respectively, refining previous chromosomal assignments. Next, the role of both chromosome regions/genes on genetic variation in IMF content and BFT was studied by 1) screening SSC4 and SSC6 for QTL affecting both traits by performing a line-cross analysis and 2) estimation of the effect of individual A-FABP and H-FABP alleles on both traits. In the first analysis, suggestive and chromosome-wise significant evidence for a QTL affecting IMF was detected on SSC6. The H-FABP gene is a candidate gene for this effect because it resides within the large region containing this putative QTL. The second analysis showed a considerable but nonsignificant effect of H-FABP microsatellite alleles on IMF content. Suggestive evidence for a QTL affecting BFT was found on SSC6, but H-FABP was excluded as a candidate gene. In conclusion, present and previous results support involvement of H-FABP gene polymorphisms in IMF accretion independently from BFT in pigs. Therefore, implementation of these polymorphisms in marker-assisted selection to control IMF content independently from BFT may be considered. In contrast to previous findings for Duroc pigs, no evidence was found for an effect of the A-FABP gene on IMF or BFT in this population.

Gerbens F ，de Koning DJ ，Harders FL ，Meuwissen TH ，Janss LL ，Groenen MA ，Veerkamp JH ，Van Arendonk JA ，te Pas MF ... -  《JOURNAL OF ANIMAL SCIENCE》

Effect of genetic variants of the heart fatty acid-binding protein gene on intramuscular fat and performance traits in pigs.

In order to find genetic markers to improve the meat quality of pigs by breeding we studied the relationship between variation in the heart fatty acid-binding protein (H-FABP) gene (FABP3) and intramuscular fat (IMF) content. To estimate the effect of H-FABP, pigs from two Duroc populations were selectively mated in such a way that at least two genotypes were present in each litter. In total, data from 983 pigs and pedigree information from three preceding generations were analyzed. Offspring were tested for IMF content as well as backfat thickness (BFT), BW, and drip loss of the meat (DRIP). All pigs were assigned to H-FABP RFLP genotype classes either by the assessed genotype (75%) or based on a probability score determined according to genotypic information of their relatives (25%). Contrasts were detected between homozygous H-FABP RFLP genotype classes for IMF content (.4%, P < .05), BFT (.6 mm, P < .01), and BW (2.4 kg, P < .10). No significant contrasts were detected for DRIP. Results for IMF content, BFT, and BW were confirmed when only genotyped animals were analyzed. Variation in BFT partially explained the effect on IMF content. Although other closely linked genes on porcine chromosome 6 might be responsible for the observed effect, interference of the halothane gene was excluded because all parental animals were noncarriers. In conclusion, H-FABP RFLP can be used as markers to select for increased IMF content and growth in breeding programs.

Gerbens F ，van Erp AJ ，Harders FL ，Verburg FJ ，Meuwissen TH ，Veerkamp JH ，te Pas MF ... -  《JOURNAL OF ANIMAL SCIENCE》

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 role 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 across 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 gene, 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 sequence-specific PCR on a cell hybrid panel, fully consistent with comparative 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 was associated with differences in IMF content and possibly growth in a Duroc population, whereas no effect on backfat thickness and drip loss of the meat 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.

Gerbens F ，Jansen A ，van Erp AJ ，Harders F ，Meuwissen TH ，Rettenberger G ，Veerkamp JH ，te Pas MF ... -  《MAMMALIAN GENOME》

Associations of heart and adipocyte fatty acid-binding protein gene expression with intramuscular fat content in pigs.

Intramuscular fat content is a major determinant of meat quality in pigs. Previously, polymorphisms in the adipocyte and heart fatty acid-binding protein genes, A-FABP and H-FABP, have been significantly associated with genetic variation of intramuscular fat content in a Duroc pig population. Further support for the role of H-FABP but not for A-FABP was found in a Meishan crossbred population. However, the effect of closely linked genes could not be excluded in these analyses. To validate the role of A-FABP and H-FABP in intramuscular fat accretion, 153 pigs of a crossbred genotype were evaluated for the A-FABP and H-FABP polymorphisms, mRNA, and protein expression levels of both FABP genes and intramuscular fat content in the longissimus lumborum muscle. For H-FABP, statistical analyses showed significant differences in mRNA but not protein expression levels between H-FABP HaeIII PCR-RFLP genotype classes. Between these genotype classes, significant differences in intramuscular fat content were found within barrows but not in gilts. Moreover, H-FABP mRNA but not protein expression levels were significantly related to intramuscular fat content. For A-FABP genotype classes, no significant differences in mRNA and protein expression levels were found. However, a significant difference in intramuscular fat content was found within barrows but not in gilts. In addition, a significant relationship between A-FABP mRNA but not protein expression levels and intramuscular fat content was found. In conclusion, variation of intramuscular fat content could not be explained by differences in A-FABP and H-FABP mRNA and protein expression levels. However, this may be due to limitations of the assays used and(or) the inappropriateness of the time of sampling. Finally, results suggest that A-FABP and H-FABP expression are translationally rather than transcriptionally regulated.

Gerbens F ，Verburg FJ ，Van Moerkerk HT ，Engel B ，Buist W ，Veerkamp JH ，te Pas MF ... -  《JOURNAL OF ANIMAL SCIENCE》

Test for positional candidate genes for body composition on pig chromosome 6.

One QTL affecting backfat thickness (BF), intramuscular fat content (IMF) and eye muscle area (MA) was previously localized on porcine chromosome 6 in an F2 cross between Iberian and Landrace pigs. This work was done to study the effect of two positional candidate genes on these traits: H-FABP and LEPR genes. The QTL mapping analysis was repeated with a regression method using genotypes for seven microsatellites and two PCR-RFLPs in the H-FABP and LEPR genes. H-FABP and LEPR genes were located at 85.4 and 107 cM respectively, by linkage analysis. The effects of the candidate gene polymorphisms were analyzed in two ways. When an animal model was fitted, both genes showed significant effects on fatness traits, the H-FABP polymorphism showed significant effects on IMF and MA, and the LEPR polymorphism on BF and IMF. But when the candidate gene effect was included in a QTL regression analysis these associations were not observed, suggesting that they must not be the causal mutations responsible for the effects found. Differences in the results of both analyses showed the inadequacy of the animal model approach for the evaluation of positional candidate genes in populations with linkage disequilibrium, when the probabilities of the parental origin of the QTL alleles are not included in the model.

OVilo C ，Oliver A ，Noguera JL ，Clop A ，Barragán C ，Varona L ，Rodríguez C ，Toro M ，Sánchez A ，Pérez-Enciso M ，Silió L ... -  《-》