Xiong Yuanzhu

Identification of Novel Polymorphisms in Porcine Ring Finger Protein 4 and Matrix Metalloproteinase 9 Genes and Association Analysis with Litter Size Traits

Reproduction trait plays an important role in pig production. Identification of molecular markers that are linked to litter size may contribute to the genetic development of porcine reproduction traits. In this study, porcine ring finger protein 4 (pRNF4) and Matrix metalloproteinase 9 (pMMP-9) were selected as candidate genes on the basis of their physiological roles in reproduction. Two single-nucleotide polymorphisms (416C>T in pRNF4 and −1257G>A in pMMP-9) that could be detected by PCR restriction fragment length polymorphism (PCR-RFLP) were discovered and tested for statistical associations with litter size traits in three populations. For 416C>T, TT genotype was associated with a significantly higher (p A, inconsistent results were found in three populations. The results suggested that T allele in pRNF4 gene might confer a high prolificacy in breeding and further studies were needed to confirm the results.

The Effects of Mx1 Locus on Immunity Tracts Components in Large White x Meishan F2 Offspring

The mouse Myxovirus resistance protein 1 (Mx1) is known to be sufficient to confer resistance to influenza viruses, and genes encoding Myxovirus resistance protein 1 (Mx1) is, therefore, an interesting candidate gene for disease resistance in farm animals. The porcine Mx1 gene has already been identified and characterized based on its homology with mouse Mx1; the full-length coding region of the pig Mx1 gene spans 2 545 bp (M65087) and is organized into 17 exons compared with the human ortholog mRNA. In this study, the exons 9, 10, 11 and introns 6, 9 of the porcine Mx1 gene were cloned and sequenced; two SNPs were identified in exons 9, 10, 11 but none of the SNPs led to an amino acid exchange, and the other eleven variants were detected in introns 6 and 9, respectively. Differences in allele frequency among Meishan, Large White, Tibetan, Tongcheng, Huainan, and Duroc pigs were observed within intron 9, of which an A → G substitution at position 186 was detected as an Msp I PCR-restriction fragment length polymorphism (PCR-RFLP). The association analysis using the Large WhitexMeishan F2 offspring suggested that the Mx1 genotype was associated with variation in several immunity traits that are of interest in pig breeding. However, further investigations in more populations are needed to confirm the above concept.

The genetic evaluation of crossbred pig populations for heterosis research by microsatellite markers

The molecular genetic characteristics were evaluated, and the genetic effects of marker loci on heterosis of three traits (birth weight, BWT; average daily gain, ADG; and feed and meat ratio, FMR) were analysed in the experimental pig populations: Yorkshire (Y, n =34), Landrace (L, n =46) and Meishan (M, n =55); Yorkshire×Landrace (YL, n =32) and its reciprocal (LY, n =36), Yorkshire×Meishan (YM, n =82) and its reciprocal (MY, n =47), by 39 microsatellite markers selected from pig chromosomes SSC4, 6, 7, 8 and 13. The results indicated that observed alleles ranged from 2 to 6, average 4.13, observed heterozygosity varied from 0.39 (Y) to 0.58 (YM+MY) and average polymorphism information content (PIC) varied from 0.33 (Y) to 0.5 (YM). There were two loci ( sw2155 and sw1037 ) at which the alleles were fixed in Y and L, and there were three loci ( sw2409 , sw2454 and sw1691 ) at which the alleles were fixed in M. The results from heterozygosity and kinship analysis revealed an intrinsic genetic relationship among the seven populations. Furthermore, the results on genetic effect analysis indicate that several marker loci had a significant effect on heterosis of the three traits in the two different F 1 crossbred populations ( P ⩽0.01), for example s0161 , swr1130 and sw1856 for BWT, sw1856 and swr2036 for ADG, and sw1302 and swr2036 for FMR. The significant marker loci implied a deep genetic relationship between molecular marker loci and heterosis.

Isolation, cDNA sequence analysis and tissue expression profile of a novel swine gene differentially expressed in the Longissimus dorsi muscle tissues from Large White × Meishan cross combination∗

In order to study the molecular mechanism of heterosis in pigs,the mRNA differential display technique was performed to investigate the differences in gene expression in the Longissimus dorsi muscle tissues from Large White×Meishan cross combination. One novel gene differentially expressed between the hybrids and the purebreds was isolated and subsequently identified using semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and its complete cDNA sequence was obtained using the rapid amplification of cDNA ends (RACE) method.The nucleotide sequence of the gene is not homologous to any of the known porcine genes.The sequence prediction revealed that the open reading frame of this gene encodes a protein of 188 amino acids that contains the putative conserved domain of the PRAl family protein and this protein has high homology with the PRA1 family protein 3 of three species-rat (88% ),human (88%),and mouse (87%),-so that it can be defined as swine PRA1 family protein 3.The phylogenetic tree analysis revealed that the swine PRA1 family protein 3 has a closer genetic relationship with the human PRA1 family protein 3 than with those of mouse and rat. The tissue expression analysis indicated that swine PRA1family protein 3 gene is highly-expressed in muscle and fat,moderately in spleen, weakly in heart,kidney,ovary,lung,and almost not expressed in small intestine and liver.The function of this gene and the relationship between this gene and heterosis are also discussed.

Differences of cytosine methylation in parental lines and F 1 hybrids of Large White×Meishan crosses and their effects on F 1 performance

In order to probe the effect of methylation on heterosis, the methylation-sensitive arbitrarily primed polymerase chain reaction (AP-PCR) technique was adopted to amplify pig genome DNA with 40 single arbitrary primers. The material involved parental lines and F 1 hybrids of Large White×Meishan crosses. Nineteen differentially methylated sites with Rsa I+ Hpa II digestion and 14 differentially methylated sites with Rsa I+ Msp II digestion between parental lines and the hybrid were found. All fragments detected in this study were grouped into four classes: (1) the same level of methylation in both parental lines and the hybrid; (2) the same level of methylation in one parent and the hybrid; (3) an increased level of methylation in the hybrid compared to the parents, and (4) a decreased level of methylation in the hybrid. Five sites had significant effects on seven traits ( P 1 performance, showing that heterosis could benefit from either expression or repression of some genes.

Relationship between individual DNA methylation percentage differences and carcass traits in pigs

In order to investigate the effects of DNA methylation on pig carcass traits, the methylation-sensitive amplified polymorphism technique (MSAP) was adopted to amplify DNA from blood samples taken from 77 F 1 hybrids of Large White×Meishan crosses. A total of 15 carcass traits were tested. Results showed that means of internal fat rate (IFR), lean meat percentage (LMP) and ratio of lean meat versus fat meat (RLF) were significantly different ( P 3 ), average backfat thickness (ABF), carcass length to the first rib (CLR) and carcass length to the first neck vertebra (CLN) were also significantly different ( P P >0.05) among five levels of neutral individual methylation percentage difference (NIMDP). Of all traits that were significantly affected by SIMPD, CW, ABF and BFT 3 increased, IFR and backfat thickness at shoulder (BFT 1 ) decreased, while CLR and bone percentage (BP) fluctuated with the SIMDP increase. The regressions between SIMDP and IFR, BFT 1 , BFT 3 and ABF were significant ( P