Research On Sequence And Polymorphism Of Porcine Mx1 And ICOS Gene

Based on QTL mapping results, pig and human comparative map and physiological or biochemical functions of genes, Mxl and ICOS genes were selected as candidate genes in this paper. These genes were isolated and identified with comparative genomics and bioinformatic approaches, etc. Association studies of the gene polymorphisms with immunity traits and production traits were performed. The main results are as follows:(1) The pig specific primers were selected from the pig EST contig constructed according to the corresponding human ICOS(Inducible T-cell co-stimulator) cDNA. The cDNA fragments of ICOS gene including ORF of Large White and Meishan breeds were obtained with cloning and sequencing. The nucleotide sequence of Large White breed has been deposited GenBank under accession number AY902753. The ICOS gene intron 2 and 3 were amplified from genomic DNA of LargeWhite and Meishan breeds. The nucleotide sequences of intron 2 and 3 were submitted to GenBank (Accession Number, intron2, LargeWhite: AY902751, Meishan: AY902752; intron3, LargeWhite: AY902749, Meishan: AY902750). Comparative sequencing of inton 2 and 3 revealed three SNPs and twenty SNPs within the two sequences respectively.(2) The exon 9 . 10 and 11 of Mxl (myxovirus) gene of LargeWhite and Meishan pig breeds were obtained with cloning and sequencing. Two cSNPs were found among these sequences, but no polymorphisms have been found. The porcine Mxl intron 6 and 9 were amplified from genomic DNA of LargeWhite and Meishan breeds. The nucleotide sequences of LargeWhite and Meishan breeds of intron 6 have been deposited GenBank under accession numbers AY902746 and AY902747; and meanwhile the nucleotide sequence of LargeWhite breed of intron 9 was submitted to GenBank with accession number AY902748.(3) Comparative sequencing of the amplified fragment revealed seven SNPs within the fragment of intron 6, And an PCR-SnaBI-RFLP was developed to detect the num.371 G/A polymorphism in intron 6; Four SNPs were detected within the fragment of intron 9 with sequences blasten,And an PCR-MspI-RFLP was established to detect the G/A polymorphism in intron 9.(4) For PCR-SnaBI-RFLP, unrelated individuals from LargeWhiteN Landrace and Meishan pig breeds and the 109 F2 animals in LargeWhite X Meishan resource family were genotyped for population variation investigations. Results showed that there were significantly different in allele frequencies between Chinese indigenous pig breed and foreign pig breeds. For PCR-MspI-RFLP, unrelated individuals from seven different pig breeds and the 121 F2 animals in LargeWhite × Meishan resource family were genotyped.Results showed that differences in allele frequencies were only detected in LargeWhite pig breed, These results offer the basis at molecular level about phenotype differences between Chinese pig breeds and foreign pig breeds.(5) Association analysis between PCR-Sna BI-RFLP and traits were performed in 109 F2 animals in LargeWhite ×Meishan resource family. For immunity traits, significant or extremely significant effects were observed for this locus on RBC, HCT, MCV, MCH, MCHC and RDW. For carcass traits, this locus was significantly associated with LEW. For meat quality traits, significant effects were observed for this locus on MCV1, MCV2, MM1, MM2.(6) Studies of the PCR-MspI-RFLP with immunity traits and carcass traits were performed in 121 F2 animals in LargeWhite × Meishan resource family. For immunity traits, significant or extremely significant effects were observed for this locus on TP, NBT, HGB, HCT, MCV, MCHC and RDW. For carcass traits, this locus was significantly associated with BP and BFT3.