Quantitative trait loci for litter size and prenatal loss in a White Duroc × Chinese Erhualian resource population

To detect quantitative trait loci (QTL) for litter size related traits, the total number of born piglets (TNB), the number of born alive piglets (NBA), the number of stillborn piglets (NSB) and the number of mummies (NM) at the first parity were recorded in 299 F₂ sows in a White Duroc × Chinese Erhualian intercross resource population. A whole genome scan was performed with 183 microsatellites distributed across 19 porcine chromosomes in the resource population, and the QTL analysis was performed with a least-squares method. A 5% genome-wide significant QTL was detected at 88 cM on pig chromosome (SSC) 15 for NBA, which also showed suggestive effect on TNB. In addition, four suggestive QTL were detected on SSC 6, 7, 8 and 15 for TNB, NBA or NSB. Two of the five QTL detected showed accordance with previous reports. No QTL was found for NM.     

MyoG基因对金华猪繁殖性状的影响

用PCR-RFLP方法对金华猪I系（109头）、II系（15头）、III系（25头）的MyoG基因的第二内含子内（PCR1- MspⅠ-RFLP）和3'-端（PCR2- MspⅠ-RFLP）位点进行了多态性分析。结果表明：PCR1- MspⅠ-RFLP位点有3种基因型（AA、AB、BB）,其基因型频率分别为0.1544,0.3826,0.4631;PCR2- MspⅠ-RFLP位点只有2种基因型（MM、MN）,其基因型频率分别为0.9953和0.0047。采用SPSS程序分析MyoG基因对金华猪繁殖性状的影响。结果表明：MyoG基因对金华母猪初胎的总产仔数、二胎的产活仔数影响显著（P<0.05）,而对其他胎次组合的总产仔数、产活仔数以及初生窝重没有显著影响（P<0.05）。     

Association of BF,RBP4, and ESR2 Genotypes with Litter Size in an Autochthonous Pig Population

The aim of the present study was to determine any potential association of the BF, RBP4, and ESR2 genes with reproduction traits in an autochthonous Greek pig population. The PCR-RFLP methodology was implemented for genotyping purposes of the examined genes. No deviation from the Hardy-Weinberg equilibrium was observed for the examined loci, while the B allele noted to be the more frequent in all analyzed genes. In addition, sows with the AA genotype of BF gene found to produce significantly lower numbers of the total born piglets (TNB) and number of piglets born alive (TNA), while the respective BB genotype significantly exceeded in TNB and NBA traits compared to the other two genotypes (P?Abbreviations: TNB: Total number of born piglets; NBA: Number of piglets born alive     

Association of EphA4 polymorphism with swine reproductive traits and mRNA expression of EphA4 during embryo implantation

The swine erythropoietin-producing hepatocellular A4 (EphA4) gene, which was detected in the endometrium during embryo implantation in pigs, was one of the potential candidate genes for reproductive traits. In the study, two single nucleotide polymorphism (SNP) loci (EphA4_1 and EphA4_2) in exon 3 of EphA4 gene were analyzed to determine whether EphA4 influenced total number born (TNB) and number born alive (NBA). Association of two diallelic polymorphisms with reproductive traits was assessed in Landrace, Yorkshire and Duroc populations with 2,014 litter records of 765 sows. The results showed that G allele at EphA4_1 locus or C allele at EphA4_2 locus seemed to have advantageous effects on litter size. And the combined analyzed results demonstrated that genotype AGTC, AGCC and GGCC are better than genotype AATT, AATC and AGTT for TNB and NBA in either single parity or all parities. The results in this study demonstrated that EphA4 gene was significantly associated with litter size in pigs. In addition, a high mRNA expression of EphA4 was found in small intestine, large intestine, stomach and endometrium, and the expression decreased during implantation in pigs. Further studies were needed to confirm these preliminary researches.     

5个与猪产仔数相关基因的效应分析

为了比较不同基因对猪产仔数效应大小,在相同的大白 （158头）、长白 （224头）猪群中采用PCR-RFLP法进行了ESR、FSHβ、PRL、PRLR、NCOA1 5种与产仔数相关基因的基因型频率检测及不同基因型的总产仔数和产活仔数效应分析,结果表明,对相同母猪群产仔数影响效应最大的是PRLR和NCOA1基因,AA型比BB型母猪总产仔数高2.28~3.33头（P<0.01）,产活仔数高1.57~3.30头（P<0.01）,其次为ESR和FSHβ基因,BB型比AA型母猪总产仔数高0.55~1.18头（P<0.05,长白例外）,产活仔数高0.37~1.20头（P<0.05）。PRL基因对产仔数效应不显著。     

Genome-wide association analysis reveals genomic regions on Chromosome 13 affecting litter size and candidate genes for uterine horn length in Erhualian pigs

Litter size has a great impact on the profit of swine producers. Uterine development is an important determinant of reproduction efficiency and could hence affect litter size. Chinese Erhualian pig is one of the most prolific breeds in the world, even though large phenotypic variation in litter size was observed within Erhualian sows. To dissect the genetic basis of the phenotypic variation, we herein conducted genome-wide association studies for total number born and number born alive (NBA) of Erhualian sows. In total, one significant single nucleotide polymorphism (SNP) (P<1.78e−06) and 11 suggestive SNPs (P<3.57e−05) were identified on 10 chromosomes, confirming seven previously reported quantitative trait loci (QTL) and uncovering six QTL for litter size or uterus length. One locus on Sus scrofa chromosome (SSC) 13 (79.28 to 90.43 Mb) harbored a cluster of suggestive SNPs associated with multiparous NBA. The SNP (rs81447100) within this region was confirmed to be significantly (P<0.05) associated with litter size in Erhualian (n=313), Sutai (n=173) and Yorkshire (n=488) populations. Retinol binding protein 2 and retinol binding protein 1 functionally related to the development of uterus were located in a region of 2 Mb around rs81447100. Moreover, four genes related to embryo implantation and development were also detected around other significant SNPs. Taken together, our findings provide a potential marker (rs81447100) for the genetic improvement of litter size not only in Chinese Erhualian pigs but also in European commercial pig breeds like Yorkshire, and would facilitate the final identification of causative variant(s) underlying the effect of SSC13 QTL on litter size.     

猪PRLR和RBP4基因多态性与产仔性能的关系

采用PCR-RFLP方法, 对莱芜黑猪、鲁莱黑猪、里岔黑猪、鲁烟白猪、新沂蒙黑猪5个山东地方/培育猪种和大约克夏、长白、杜洛克3个引进猪种共8个猪种323头繁殖母猪进行PRLR和RBP4基因的多态性检测, 并采用最小二乘法分析其对产仔数影响的遗传效应。结果表明: 两个基因位点在8个猪种的测定群体中均存在多态性, 但山东地方/培育猪种与引进猪种间在基因型频率上存在较大差异。PRLR和RBP4基因对产仔数性状有显著影响(P<0.05), AA均为优良基因型。对于PRLR基因, 山东地方/培育猪种内AA基因型母猪的总产仔数和活产仔数比BB基因型母猪平均多产1.03头和0.89头, 引进猪种中AA基因型母猪比BB基因型母猪平均多产分别为1.26头和1.11头。对于RBP4基因, 山东地方/培育猪种内AA基因型母猪的总产仔数和活产仔数比BB基因型母猪平均多产0.59头和0.51头, 引进猪种中AA基因型母猪比BB基因型母猪平均多产分别为0.72头和0.64头     

Effect of VNTR polymorphism of the Muc1 gene on litter size of pigs

An investigation was undertaken to study the association between the variable number of tandem repeats polymorphism of the Muc1 gene and the litter size in pigs. Four different alleles were found in three breeds. The sequence analysis shows that the repetitive region of pig Muc1 gene is an array of 108-bp repeats. A total of 2,430 litter records from 897 sows genotyped at Muc1 gene were used to analyze the total number born (TNB) and number born alive (NBA). The study of the effects on litter size suggests that TNB and NBA of genotype AA are the highest in Large White, and the TNB and NBA of the third to ninth parities are 1.61 and 2.29 piglets per litter higher (P < 0.05) than those of the genotype DD, respectively. In Landrace, TNB and NBA of the genotype AA are 1.68 (P < 0.01) and 1.58 (P < 0.05) piglets per litter higher than those of the BB genotype in the third to ninth parities, but for all parities the TNB of genotype AA were 0.76 piglets per litter (P < 0.05) higher than BB. In Duroc, the TNB and NBA of genotype AA are about 1.5 piglets per litter more than those of DD in the third to ninth parities, though not significantly. The research suggests that the smaller allele tends to have higher litter size. The results indicate that Muc1 gene is significantly associated with litter size in pigs.     

Identification of new single nucleotide polymorphisms affecting total number born and candidate genes related to ovulation rate in Chinese Erhualian pigs

The Chinese Erhualian pig has the highest record for litter size in the world. However, the genetic mechanism of its high prolificacy remains poorly understood. In our study, large phenotypic variations in litter size were found among Erhualian sows. Significant differences in total number born (TNB) and corpora lutea numbers were observed between sows with high and low estimated breeding values (EBVs) for TNB. To identify single nucleotide polymorphisms (SNPs) associated with TNB, a selective genomic scan was conducted on 18 sows representing the top 10% and 18 sows representing the bottom 10% of EBVs of 177 sows using Illumina Porcine SNP60 genotype data. Genome‐wide fixation coefficient (F_ST) values were calculated for each SNP between the high‐ and low‐EBV groups. A total of 154 SNPs were significantly differentiated loci between the two groups. Of the top 10 highest F_ST SNPs, rs81399474, rs81400131 and rs81405013 on SSC8 and rs81434499 and rs81434489 on SSC 12 corresponded to previously reported QTL for litter size. The other five SNPs, rs81367039 on SSC2, rs80891106 on SSC7, rs81477883 on SSC12 and rs80938898 and rs80971725 on SSC14, appeared to be novel QTL for TNB. Significant associations between rs81399474 on SSC8 and TNB were confirmed in 313 Erhualian sows. Forty genes were identified around the top 10 highest F_ST SNPs, of which UCHL1, adjacent to rs81399474, and RPS6KB1 and CLTC, adjacent to rs81434499, have been reported to affect the ovulation rate in pig. The findings can advance understanding of the genetic variations in litter size of pigs.     

Sequencing and gene expression of the porcine ITIH SSC13 cluster and its effect on litter size in an Iberian × Meishan F2 population

The aim of the present study was to identify polymorphisms and to analyze endometrial gene expression of the porcine SSC13 ITIH cluster that could explain differences in prolificacy of 255 F(2) sows derived from an Iberian (Ib)×Meishan (Me) intercross in which QTL for the number of piglets born alive (NBA) and total number of piglets born (TNB) were previously detected on this chromosome. Sequencing of ITIH-1, -3, and -4 mRNAs was done and several polymorphisms segregating within the Ib×Me population were found in all three genes. Significant associations with NBA were found for two SNPs from ITIH-1, four from ITIH-3, and four SNPs from ITIH-4 (p<0.05). Haplotypes for the significant SNPs were calculated by segregation analysis and a marker assisted association test indicated that the alleles coming from the Meishan breed had a favorable effect on NBA for all three genes. Interestingly, some of the significant SNPs were located within the von Willebrand domain of the ITIH proteins, the binding site of molecules essential for the synthesis of the extracellular matrix during cumulus expansion. Gene expression analyses also revealed differences in the expression level of the ITIH-3 gene regarding the prolificacy performance (high or low) and the uterus sample (apical or basal).