The Genetic Effect Analysis Of Porcine MAN2B2, MSR,RGS12 Gene Affecting Reproduction Traits

The economic efficiency of swine industry is influenced by litter size deeply. According to QTL mapping results, pig and human comparative map and physiological or biochemical functions of genes, three candidate genes were selected: MAN2B2 (a-Mannosidase2,B2), RGS12 (regulators of G protein signaling 12) , mSR (membrane steroid receptor). These genes were isolated and identified with comparative genomics and bioinformatic approaches, etc. Qingping, New Qingping line, Chinese lean type new line DⅣ1, DⅣ 2were used in this study. The relationship of the polymorphism of the genes and association studies of the gene polymorphism with reproduction traits were investigated. The main results are as following:1. The analysis results of genetic effect of MAN2B2 geneThe partial genomic sequence MAN2B2 gene of Meishan, Qingping, Large White, Duroc pig breeds were obtained and had been deposited GenBank under accession number AY847942, AY847943, AY847944, AY847945, respectively. Comparative sequencing of these four breed amplified fragments revealed six single nucleotide polymorphisms (SNPs), an PCR-Msp I -RFLP was developed to detect C/T substitution.For PCR-Msp I -RFLP, genotype BB was detected only in Chinese pure breed Qingping and Meishan during 7 different breeds and lines from the description of the frequencies of genotype and alles. The result of x~2 showed that there was no significant difference between Qingping and Meishan breeds, but both of them had significant difference with other groups.78 Qingping breed and 69 New Qingping line were genotyped for population variation investigation and association analysis with reproduction. Results showed that there was significantly difference between genotype AA and BB with litter size in later parities in Qingping breed. Genotype BB has more 1.74 piglets/litter than genotype AA, and the additive effect is significant (P<0.05).2. The analysis results of genetic effect of mSR geneThe partial nucleotide sequences in exon2 of mSR gene of Meishan, Large White, Qingping pig breeds were obtained with cloning and sequencing. Comparative sequencing of the amplified fragments revealed 18 SNPs. An PCR-Msp I -RFLP was developed to detect the A/G substitution which resulted in amino acid change. PCR-Hha I -RFLP was developed to scan another SNP which didn't result in amino acid change.Both Hha I -RFLP and Msp I -RFLP have three genotypes in four different breeds and lines which were used to study allele frequencies. The frequencies between allele A and B have lager difference in New Qingpin line and Qingping breed, respectively. The result of X2 showed that there was no significant difference between breed Qingping and New Qingping line, but both of them had significant difference with DlVland DlV21ines.Association analysis in 165 Qingping population and 187 Chinese line type DIV showed significant difference between genotype AA and BB of litter size in New Qingping line and Chinese lean type new line DIV, but in former genotype AA has significant difference with genotype BB which additive effect is 1.21±0.58(P<0.01), while in Qingping breed they had difference(P<0.05), which additive effect was -1.32±0.19.From the description of the frequencies of genotype and alleles in four groups, three genotypes were detected. Qingping breed had the largest difference in the allele frequence. The result of x2 showed that there was no significant difference between breed Qingping and New Qingping line, but both of them had significant difference with DIV1 and DIV2 lines.Association analysis in Qingping breed and Chinese lean type new line DIV in the first parity showed significant difference between Msp I -RFLP genotypes and number of stilibom pigs(NSP) (P<0.01), and the additive effect was significant(P<0.05).3. The analysis results of genetic effect of RGS12 geneBased on the report that RGS12 gene which was mapped at pig chromosome 8 was linked with satellite SB73 firmly, we investigated association of RGS12 gene SSR polymorphism with reproduction traits by using least square analysis in 65 Qingping breed and New Qingping line which had reproduction records. Results showed that the difference between different genotypes with reproduction traits was not significant(P>0.05).Use of the candidate gene information in marker assisted selection or introgression improves the litter size of pigs more efficiently.