Profiling the genome-wide DNA methylation pattern of porcine ovaries using reduced representation bisulfite sequencing.

Substantial evidence has shown that DNA methylation regulates the initiation of ovarian and sexual maturation. Here, we investigated the genome-wide profile of DNA methylation in porcine ovaries at single-base resolution using reduced representation bisulfite sequencing. The biological variation was minimal among the three ovarian replicates. We found hypermethylation frequently occurred in regions with low gene abundance, while hypomethylation in regions with high gene abundance. The DNA methylation around transcriptional start sites was negatively correlated with their own CpG content. Additionally, the methylation level in the bodies of genes was higher than that in their 5' and 3' flanking regions. The DNA methylation pattern of the low CpG content promoter genes differed obviously from that of the high CpG content promoter genes. The DNA methylation level of the porcine ovary was higher than that of the porcine intestine. Analyses of the genome-wide DNA methylation in porcine ovaries would advance the knowledge and understanding of the porcine ovarian methylome.

[Founding and genetic analysis of Landrace x Lantang pig resource population for QTL mapping].

With F2 design, 16 Chinese Lantang sows crossbred with eight highly improved Landrace boars to establish a resource population including 40 F1 sows, eight F1 boars, and 232 F2 pigs. Genetic analysis of the resource population showed that the 32 performance traits displayed some degree of variation, and coefficients of variation of the majority of economic traits exceeded 10%. The variance component analysis revealed that the ratios of additive genetic variance to phenotypic variance of the majority of economic traits were high. Of the 22 microsatellite DNA markers, only 12 microsatellite DNA markers are polymorphisic in this populations. The average heterozygosity of these markers and PIC were 0.53 and 0.46 respectively. The results showed that these markers can provide enough information for QTL mapping. In conclusion,the F2 pigs were sufficiently segregated, and were capable of serving as a resource population for QTL mapping.

Genetic effects of IGF-1 gene on the performance in Landrace x Lantang pig resource population.

A Landrace x Lantang resource population (LL-SCAU) including 216 F2 pigs was founded by F2 design for analysis of IGF-1 gene polymorphism by PCR-RFLP. The least square means of divergent IGF-1 genotypes for the measured traits were estimated with the fixed model. The genetic effects of IGF-1 gene were estimated with a mixed model and the additive and dominant effects of IGF-1 gene were accordingly calculated. The results of the fixed model and the mixed model showed that IGF-1 locus significantly affected average daily gain after weaning. Average daily gain after weaning for AA genotype on IGF-1 locus was 20.58 g (P = 0.0347) higher than for AB. The additive and dominant effects attributed to IGF-1 were 1.78 g and -18.81 g respectively. IGF-1 locus also significantly affected carcass composition. Bone percentages for AA and AB on IGF-1 locus were lower than for BB by 5.22% (P = 0.0008) and 5.19% (P = 0.0007) respectively, and the additive and dominant effects were -2.61% and -2.58% respectively. Amount of carcass lean for AA on IGF-1 locus was less than for AB by 0.45 kg (P = 0.0264), and the additive and dominant effects were 0.16 kg and 0.61 kg respectively. Skin and fat percentage for AA and AB on IGF-1 locus was higher than for BB by 8.81% (P = 0.0206) and 7.64% (P = 0.0431) respectively, and the additive and dominant effects were 4.41% and 3.24% respectively. The genetic analysis of IGF-1 gene showed that IGF-1 locus significantly affected average daily gain after weaning, bone percentage, carcass lean, skin and fat percentage. The estimated additive and dominant effects showed that only the additive effect of IGF-1 locus on skin and fat percentage was much higher than dominant effect, and IGF-1 gene can be used as a major gene for effective selection of these traits.