Molecular characterization, expression patterns, and promoter activity analysis of PGM1 in pigs.

The phosphoglucomutase 1 (PGM1) gene was differentially expressed in tissues of Chinese Meishan and Large White pigs. In this study, the promoter region, expression profile, and genetic mutations of the gene were determined. Expression of a 5'-deletion in both C2C12 and PK-15 cells showed that a negative regulatory element was at -1871 to +185 bp and a positive regulatory element was at -1158 to +185 bp. Among the different types of muscle fibers, PGM1 had the highest expression in both longissimus dorsi and biceps femoris. The expression was concentrated in the muscle fibers at different growth stages of Meishan and Large White pigs. The synonymous mutation C462T in the coding sequence was confirmed by polymerase chain reaction-restriction fragment length polymorphism, and the frequency of the C allele was dominant in Chinese indigenous breeds. Association analysis with lean meat showed that the C462T site was different.

Differential expression and effect of the porcine ANGPTL4 gene on intramuscular fat.

In a previous study, we investigated differences in gene expression in backfat between Meishan and Large White pigs and their F1 hybrids, Large White x Meishan, and Meishan x Large White pigs. One potential differentially expressed sequence tag from the mRNA differential display was a homolog of the human angiopoietin-like 4 (ANGPTL4) gene, which encodes a protein that is secreted by both liver and white adipose tissues and can inhibit lipoprotein lipase activity and stimulate white adipose tissue lipolysis. Here, ANGPTL4 mRNA was found to be upregulated in the backfat of Large White compared with that in the Meishan pigs and the F1 hybrids, Meishan x Large White and Large White x Meishan, whereas expression was lowest both in the longissimus dorsi and the heart, as shown by the tissue distribution profile. Only one mutation, a G/A transition located in the third intron, was found. The ANGPTL4 G/A polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) showed a significant effect on intramuscular fat (IMF), water moisture of the longissimus dorsi, meat marbling of the longissimus dorsi, and pH of the longissimus dorsi (P < 0.05). This site seemed to be significantly (P < 0.05) additive in its actions on IMF, water moisture, and pH, whereas it showed significant dominance in its action on meat marbling (P < 0.05). This locus can be potentially considered as a marker for IMF improvement.

Transcriptional analysis of the porcine TTID gene and association of different TTID genotypes with carcass traits.

The titin immunoglobulin domain (TTID) protein localizes to the Z line in muscle and binds to alpha-actinin and gamma-filamin. It plays an indispensable role in stabilizing and anchoring of thin filaments. In this study, the 5'-regulatory region of the porcine TTID gene was analyzed with bioinformatic methods. Another objective of this study was to further investigate the polymorphism in the intron 6 of the porcine TTID gene. We determined allele frequency among six Chinese porcine purebreds. The polymorphisms were genotyped in a population of 280 F2 pigs representing two Large White x Meishan reference families. Different TTID genotypes were significantly associated with carcass traits, including skin percentage (P < 0.05), loin eye area (P < 0.05), and average skin thickness (P < 0.01). Our study will continue to lay the groundwork for further investigations into the detailed function of the porcine TTID gene.

Expression patterns and promoter activity analysis of UGP2 in pigs.

The function of the UDP-glucose pyrophosphorylase 2 gene (UGP2) in pig is not clear. In the present study, we used RNA isolated from Large White pigs and Chinese indigenous MeiShan pigs to examine the temporal coordination of changes in gene expression within muscle tissues. We cloned both the complete genomic DNA sequence and 2077-bp 5ꞌ-flanking sequence of porcine UGP2, to determine the genomic sequence. Real-time RT-PCR revealed that UGP2 was highly expressed in liver and skeletal muscle of MeiShan pigs. Among different types of muscle fibers, the UGP2 had the highest expression in both soleus muscle and longissimus dorsi in Large White pigs. In the progression of muscle fibers at different growth stages, UGP2 plays a role in the early days after birth in Large White pigs, while in MeiShan pigs it is important later. Furthermore, the 5ꞌ-flanking sequence we cloned exhibited the promoter activity of UGP2, and the sequence 588 bp upstream from the transcriptional site had the greatest activity.

Detection of novel SNPs and mapping of the fatness QTL on pig chromosome 7q1.1-1.4 region.

Many QTLs for fatness traits have been mapped on pig chromosome 7q1.1-1.4 in various pig resource populations. Eight novel markers, including seven SNPs and one insertion or deletion within BTNL1, COL21A1, PPARD, GLP1R, MDFI, GNMT, ABCC10, and PLA2G7 genes, as well as two previously reported SNPs in SLC39A7 and HMGA1 genes, were genotyped in Large White and Meishan pig breeds. Except for two SNPs in HMGA1 and ABCC10 genes, allele frequencies of the other eight markers are highly significant different between Chinese indigenous Meishan breeds and Large White pig breeds. Eight polymorphic sites were then used for linkage and QTL mapping to refine the fatness QTL in a Large White × Meishan F(2) resource population. Five chromosome-wise significant QTLs were detected, of which the QTLs for leaf fat weight, backfat thickness at 6-7th rib and rump, and mean backfat thickness were narrowed to the interval between PPARD and GLP1R genes and the QTL for backfat thickness at thorax-waist between GNMT and PLA2G7 genes on SSC7p1.1-q1.4.