Association between MC1R gene and coat color segregation in Shanxia long black pig and Lulai black pig.

BACKGROUND: Coat color, as a distinct phenotypic characteristic of pigs, is often subject to preference and selection, such as in the breeding process of new breed. Shanxia long black pig was derived from an intercross between Berkshire boars and Licha black pig sows, and it was bred as a paternal strain with high-quality meat and black coat color. Although the coat color was black in the F1 generation of the intercross, it segregated in the subsequent generations. This study aims to decode the genetic basis of coat color segregation and develop a method to distinct black pigs from the spotted in Shanxia long black pig. RESULTS: Only a QTL was mapped at the proximal end of chromosome 6, and MC1R gene was picked out as functional candidate gene. A total of 11 polymorphic loci were identified in MC1R gene, and only the c.67_68insCC variant was co-segregating with coat color. This locus isn't recognized by any restriction endonuclease, so it can't be genotyped by PCR-RFLP. The c.370G > A polymorphic locus was also significantly associated with coat color, and has been in tightly linkage disequilibrium with the c.67_68insCC. Furthermore, it is recognized by BspHI. Therefore, a PCR-RFLP method was set up to genotype this locus. Besides the 175 sequenced individuals, another more 1,391 pigs were genotyped with PCR-RFLP, and all of pigs with GG (one band) were black. CONCLUSION: MC1R gene (c.67_68insCC) is the causative gene (mutation) for the coat color segregation, and the PCR-RFLP of c.370G > A could be used in the breeding program of Shanxia long black pig.

Genetic variation of porcine prostaglandin-endoperoxide synthase 2 (PTGS2) gene and its association with reproductive traits in an Erhualian x Duroc F2 population.

Identification of major genes that genetically impact female fertility is important for successful selection of high prolificacy pig lines. Because it is the rate-limiting enzyme in the conversion of arachidonic acid to prostaglandins (PGs), which are important for ovulation, fertilization, implantation, decidualization and parturition, prostaglandin-endoperoxide synthase 2 gene (PTGS2) is a potential candidate gene affecting porcine reproductive traits. In this study, a PCR-RFLP was used to genotype a total of 1 031 animals, including 661 from twelve Chinese local pig breeds, 190 from three Western pig breeds and 180 F2 sows from Nanchang pig resource family. Differences in frequency distributions of PTGS2 among twelve Chinese and three Western pig breeds and populations generally agree with their prolificacy. The allele frequencies in Lower Changjiang River Basin Type pig breeds, North China Type and Central China Type breeds are significantly different from those in South China Type, Plateau Type and Western pig breeds (P<0.001). And no significant differences were observed among Lower Changjiang River Basin Type, North China Type, Central China Type pig breeds, between South China Type and Western pig breeds, in part because of similar fertility patterns. And notable associations as well as reliable additive and dominant effects were not detected in an Erhualian x Duroc F2 population (P>0.05). Whereas, there is a trend for animals with one copy of the favourable A allele to have an increased TNB (total number of piglet born) and TBA (the number of piglets born alive) and a decreased SB (stillborn pigs) trait. Considering its crucial role in reproductive pathways, the PTGS2 gene deserves further study.

Genetic variations of the porcine PRKAG3 gene in Chinese indigenous pig breeds.

Four missense substitutions (T30N, G52S, V199I and R200Q) in the porcine PRKAG3 gene were considered as the likely candidate loci affecting meat quality. In this study, the R200Q substitution was investigated in a sample of 62 individuals from Hampshire, Chinese Min and Erhualian pigs, and the genetic variations of T30N, G52S and V199I substitutions were detected in 1505 individuals from 21 Chinese indigenous breeds, 5 Western commercial pig breeds, and the wild pig. Allele 200R was fixed in Chinese Min and Erhualian pigs. Haplotypes II-QQ and IV-QQ were not observed in the Hampshire population, supporting the hypothesis that allele 200Q is tightly linked with allele 199V. Significant differences in allele frequencies of the three substitutions (T30N, G52S and V199I) between Chinese indigenous pigs and Western commercial pigs were observed. Obvious high frequencies of the "favorable" alleles 30T and 52G in terms of meat quality were detected in Chinese indigenous pigs, which are well known for high meat quality. However, the frequency of the "favorable" allele 199I, which was reported to have a greater effect on meat quality in comparison with 30T and 52G, was very low in all of the Chinese indigenous pigs except for the Min pig. The reasons accounting for this discrepancy remain to be addressed. The presence of the three substitutions in purebred Chinese Tibetan pigs indicates that the three substitutions were ancestral mutations. A novel A/G substitution at position 51 in exon 1 was identified. The results suggest that further studies are required to investigate the associations of these substitutions in the PRKAG3 gene with meat quality of Chinese indigenous pigs, and to uncover other polymorphisms in the PRKAG3 gene with potential effects on meat quality in Chinese indigenous pigs.

Research on the genetic variations of a1-fucosytransferase (FUT1) gene in 26 pig breeds.

Enterotoxigenic Escherichia coli F18(ECF18) is a main pathogen that causes edema disease and post-weaning diarrhoea in piglets, and al-fucosytransferase (FUT1) gene has been identified as a candidate gene for controlling the expression of the receptor for ECF18 bacteria. The genetic variations at position 307 nucleotide in open reading frame of FUT1 gene in 26 pig breeds (total 1458 individuals) from 5 western commercial pig breeds and 21 Chinese native pig breeds were investigated by PCR-RFLP. The results showed that the genetic polymorphisms of the FUT1 locus were only detected in 5 western pig breeds and the Chinese Lingao pig breed, 5 western pig breeds possessed 3 different genotypes, and Lingao pig breed had two susceptible genotypes GG and AG, while all the other 20 Chinese native pig breeds only presented the susceptible genotype GG. The results indicated that if M307G-A point mutation in the coding region of FUT1 gene was the key factor determining the expression of the ECF18 receptor, most of Chinese native pig breeds were absent of the genetic background on the resistance to ECF18 bacteria. In this case, it was inferred that the resistance gene to ECF18 might be originated from western pig breeds. In addition, it is of great importance for the conservation of Lingao pig breed as it is the only found Chinese native pig breed possessing resistance M307A allele in FUT1 gene. Generally, compared with exotic pig breeds, Chinese native pig breeds have stronger resistance to edema disease and post-weaning diarrhoea in piglets. The results suggested that further study should be done to identify and characterize putative QTL (quantitative trait locus) or/and the functional gene responsible for the resistance to ECF18 in Chinese native pig breeds.

[Polymorphism analysis of porcine myogenin gene by PCR-RFLP].

The polymorphisms of porcine myogenin gene in 561 pigs including Duroc, Landrace, Large Yorkshire, Nanchang white pig, Erhualian, Meishan, Yushan black pig, Leping spotted pig, Jinhua black head-hind pig and Shanggao black head-hind pig were detected by PCR-RFLPs with three different pairs of primers,and the PCR products were digested by MspI. The results showed that most of the Duroc, Landrace, Large Yorkshire, Nanchang white pigs presented as AA genotype, while more animals of the six Chinese local pig breeds except for Leping spotted pig presented as BB genotype at PCR1 MspI-RFLP site. The six Chinese local breeds presented as MM genotype except that one Yushan black pig presented as MN genotype, while more swines of the exotic breeds including Duroc, Landrace, Large Yorkshire presented as NN genotype, and Nanchang white pig appeared to be closer to the exotic breeds at PCR2 MspI-RFLP site. PCR product was obtained in all the swine by PCR3, but the MspI restriction site was not found in the tested pig breeds including Meishan and blood closely related Erhualian pig.