3-hydroxy-3-methylglutaryl-Coenzyme A reductase (HMGR) is the rate-limiting enzyme for cholesterol synthesis. Its activity is regulated via a negative feedback mechanism through sterols and non-sterol metabolites derived from mevalonate, the product of the reaction catalyzed by reductase. Here, we cloned a full-length transcript of porcine HMGR by RT-PCR and RACE. The porcine HMGR cDNA (2864 bp,GenBank accession no. DQ432054) contains a 2658 bp open reading frame and shares 91% identify with those of human and cattle, and 85%, 85% and 84% identify with the HMGR coding sequences of Norway rat, golden hamster, and house mouse, respectively. The deduced porcine HMGR protein consists of 885 amino acids with a calculated molecular mass of 97.15 kDa(GenBank accession no. ABD96089). The amino acid sequence similarities correspond to 95%, 95%, 92%, 92% and 92% when compared with human, cattle, Norway rat, golden hamster and house mouse sequences, respectively. The structure and function of HMGR deduced protein product were predicted by bioinformatic approaches. HMGR-specific transcripts were found in 15 different tissues from pig by RT-PCR and Real-time PCR. The relative expression level of HMGR was high in liver, heart, kidney, bladder and subcutaneous fat, medium in lung, uterus and large intestine, and low in cerebrum, spleen, spinal cord, stomach, ovary, longissimus muscle, and small intestine. The SNPs analysis of HMGR showed that there were five SNPS and three of them are synonymous mutations and the other two are missense mutations. Taken together, our data may lay a ground for further investigation of HMGR's functions and regulatory mechanisms in swine.

DNA polymorphism of the porcine leukemia inhibitory factory (LIF) was investigated and used to study the effects on litter size in Large White pigs. A total of 2,167 litter records from 420 sows genotyped at two SNP loci (LIF1 and LIF2) within LIF gene were analyzed to determine whether LIF influenced total number born (TNB) and number born alive (NBA). The results indicated that B allele at LIF1 locus and A allele at LIF2 locus seem to have advantageous effects on litter size. However, the combined analyzed results demonstrated that genotype AAAA, ABBB, and BBBB are better than genotype AAAB, AABB, and ABAB for TNB and NBA in either third to eighth parity or all parities. In all parities, the sows with AAAA genotype had an advantage of 1.76 piglets (P < 0.001) for TNB and 1.44 piglets (P < 0.01) for NBA per litter over the AAAB sows, respectively. The results in this study demonstrated that LIF gene was significantly associated with litter size in pigs.

The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) is an essential enzyme in cholesterol biosynthesis. To study the expression of HMGR and corresponding cholesterol content in liver, adipose and muscle, six Chinese local breed (Huai pig) and Landrace pigs were selected. The results indicated that significant differences of cholesterol content in adipose (P < 0.01), liver (P < 0.05) and muscle (P < 0.01) tissues were detected between pigs of differing genetic backgrounds. HMGR mRNA expression were noted for adipose, liver and muscle of the two vastly differing genetics. Moreover cholesterol content differed (P < 0.01) among tissues across breed. Likewise, HMGR mRNA expression was different between adipose and liver tissues, muscle and liver tissues in both breeds; however, no difference was noted between adipose and muscle tissues. Results from this study indicate that cholesterol content and HMGR mRNA expression are higher in Huai pig tissues suggesting this gene is expressed in a breed- and tissue-dependent manner in pigs. Understanding the causes of variation in HMGR gene expression may provide crucial information about cholesterol biosynthesis.

The complete open reading frame 5 (ORF5) sequences of 34 field porcine reproductive and respiratory syndrome virus (PRRSV) isolates from China in 2002–2007 were detected and compared with the different variable Chinese isolates S1, CH-1a, HB-1, HB-2 and JXA1. The results showed that all isolates were of type 2 PRRSV and could be assigned to two clusters. The isolates in cluster sg1 was high similar with the highly pathogenic PRRSV strain JXA1, while sg2 clustered with type 2 PRRSV isolate VR2332. It was interesting that the isolate SH02 which was isolated from Shanghai in 2002 has 98.8% identity with JXA1 emerged in 2006. And the ZJJ07 isolate was found to be a natural recombinant between a Chinese highly pathogenic SY0608 isolate and a VR-2332 derivative NH04 isolate. Analysis of the potential glycosylation sites indicated that they were frequently mutated and formed five putative N-linked glycosylation (NGS) sites patterns based on N30, 33–35, 44 and 51 in those isolates. It indicated that the highly variable PRRSV strain with different NGS patterns spread widely in China. The great genetic diversity could be taken into consideration for the control and prevention of this disease.

The objective of this study was to determine whether peroxisome proliferator-activated receptor gamma (PPAR gamma) is involved in the regulation of weaning to estrus of primiparous sows. Twelve sows composed of 6 groups of 2 full-sibs in a similar age (325.2 d), body weight (BW; 152.4 kg) and backfat thickness (BFT; 27.0 mm) at start of lactation, were allocated to accept 31 MJ (restricted group, R-group) or 53 MJ (control group, C-group) DE/d treatment, respectively. The experimental results indicated that the low energy intake resulted in excessive losses of BW and BFT during lactation in R-group sows, which may be related to decrease of serum 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), a ligand of PPAR gamma. The obvious peak and the frequency of LH, FSH and estradiol (E-2) were only observed in C-group sows. Except for E-2 at d 1 and 2, serum FSH, LH and E-2 concentrations in R-group were lower than those in C-group sows after weaning. However, the serum progesterone (PQ) level in R-group sows was always more than that in C-group. The expression abundances of PPAR gamma and GnRH receptor (GnRH-R) in pituitary, FSH receptor (FSH-R), LH receptor (LH-R), estrogen receptor (ES-R) and aromatase in ovary of anestrous sows were lower than those of estrous sows. Neither the BFT nor the BW was associated with the mRNA abundance of PPAR gamma in hypothalamus during lactation. Expressions of PPAR gamma in pituitary and ovary were affected evidently by the BFT changes and only by the loss of BW of sows during and after lactation. Furthermore, PPAR gamma mRNA level in ovary was significantly related to the expression abundances of GnRH-R, FSH-R, ES-R and aromatase, and GnRH-R was obviously associated with PPAR gamma expression in pituitary. However, PPAR gamma expression in hypothalamus likely has no effects on these genes expression and no obvious difference for all sows. Not serum E-2 or P-4 alone but the ratios of E-2 to PQ and 15d-PGJ(2) to P-4, and serum FSH and LH were evidently related to PPAR gamma expression in pituitary and ovary. It is concluded that PPAR gamma is associated with body conditions, reproduction hormones and their receptor expression, which affected the functions of pituitary and ovary and ultimately the estrus after weaning of primiparous sows.

Two pairs of primers were designed based on the known sequence in GenBank for amplification of MTNR1A gene in a Large White and a Landrace herd. Using PCR-SSCP (single strand conformation polymorphism), we found a single nucleotide polymorphism(SNP) within the product amplified from the first pair of primers. PCR products from randomly selected different genotypes were sequenced after were recovered and purified. Results revealed a synonymous single base mutation(G-->A) at +159bp(sequence numbering based on Genbank accession number U73326) for the BB genotype. When analyzed for association with litter size traits, this MTNR1A SNP was found to have no significant effect on litter size traits.

The polymorphisms of ESR1, FSHB and RBP4 genes were detected by PCR-SSCP, PCR and PCR-RFLP in a Large White and a Landrace herd in Beijing, China and the influence of ESR1, FSHB and RBP4 on litter size traits was analyzed using three models. We found polymorphisms for the three genes in Large White besides for ESR1 and RBP4 genes in Landrace, The results showed that the most genotype effects are of ESR1 among these three genes.