Obese and lean pig breeds show obvious differences in adipose metabolism/fat deposition; however, the molecular mechanism underlying phenotype variation remains unknown. In order to understand it, we analyzed the differences of gene expression in backfat between Meishan (a typical Chinese indigenous obese breed) and Large White (a lean Western breed) pigs. Here, we cloned porcine β subunit of IDH3 (IDH3B) and 2447 bp 5'-flanking sequence of this gene, and determined the genomic structure. Porcine IDH3B contains three isoforms, IDH3B ( 1 ), IDH3B ( 2 ) and IDH3B ( 3 ). Real-time RT-PCR revealed that these three isoforms were prevalently up-regulated in backfat of western commercial pigs, Large White, Landrace and Duroc, compared with Chinese indigenous breeds, Meishan and Tongcheng pigs. A 304 bp insertion/deletion variant was found in the 5'-flanking region. Dual-luciferase reporter assays showed that in vitro the promoter of IDH3B gene with the insertion had higher luciferase activity as compared with the wild type. Three genotypes AA, AB and BB, due to this insertion, were detected, and the frequency of allele A was dominant in western commercial pigs, whereas allele B predominated in Chinese indigenous breeds. IDH3B mRNA expression in Meishan pigs was more abundant with genotype AA than with genotype AB or BB, as in Large White pigs. In addition, the polymorphism was detected in 317 pigs of a Large White × Meishan F2 resource population. Association analysis showed that pigs with genotype AA possessed higher backfat thickness at buttocks than those with genotype AB (P < 0.05) or BB. These data suggested that the 304 bp insertion mutation in promoter region increased the expression of porcine IDH3β transcripts and this mutation might be a candidate marker for marker assistant selection in swine breeding.

H2A histone family, member Z (H2A.Z) is required for early mammalian development. In the present study, the 932 bp of full-length cDNA encoding a 128 amino-acid protein and the sequences of intron 2 to 4 of the porcine H2A histone family, member Z (pH2AFZ) gene were obtained. By comparative sequencing of pH2AFZ gene in Large White and Meishan pigs, a 4 bp deletion/insertion in intron 2 was detected and a PCR-Bsu15I-RFLP was established to detect this variation. In DIV (4th Dam line of Chinese lean-type new lines) pigs, the first-parity females with AA genotype had fewer piglets born alive (22.64 and 21.83 piglets per litter) than those with AB ( P , 0.01) and BB ( P , 0.05) genotype. The additive allelic and dominance effect were estimated to be 0.92 ( P , 0.05) and 20.87 piglets per litter ( P , 0.01) for number of piglets born alive, respectively. This result suggests that the pH2AFZ gene might be a good candidate gene of litter-size trait and provides some marker information for marker-assisted selection.

ABSTRACT. 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 F 2 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.