Polymorphism Of The SLA-DRA Gene And Its Correlation With Piglet Diarrhea

On the base of the serious threat form piglet diarrhea in the swine industry andthe vital function of SLA II genes in body’s immune systems, this study wasdesignated to explore the polymorphisms of the4functional exon regions inSLA-DRA gene and its association with piglet diarrhea by PCR-SSCP, cloning andsequencing from three imported commercial pig strains (Landrace, Large White andDuroc), in order to provide baseline information for breeding to enhancedisease-resistance of swine. The major conclusions are as follows:1. In the three pig populations, no polymorphisms were detected in exon3of theDRA locus. Six genotypes (AA, AB, BB, AC, CC and BC) representing three specificallele (A, B and C) were detected in both exon1and exon2site, with sequenceanalysis revealing three and two nucleotide substitutions, respectively. Sevengenotypes (AA, AB, BB, BC, BD, CE and CF) representing six specific allele (A to F)were detected in exon4site, with sequence analysis revealing six nucleotidesubstitutions.2. Five mutations c.178G>A, c.211T>C, c.4081T>C, c.4184A>G andc.4293G>A were found for the first time in swine, which formed four novel allelesequences: SLA-DRA*E1a, SLA-DRA*E1b, SLA-DRA*E4e and SLA-DRA*E4fandhave been submitted to the GenBank database and assigned the accession numberJX135565, JX135566, JX135567and JX135568.3. At exon4locus, the He and PIC of Duroc were lowest (0.19), indicatingminimized genetic variation and low polymorphism of Duroc in exon4of SLA-DRAgene; the He and PIC in other loci of different pig strains were ranged from0.51to0.67and0.4to0.59, respectively, indicating abundant genetic diversity in these lociwithin different populations.4. Chi-square test showed that genotypic distribution were significantly differentamong Duroc and other two pig strains in all three site (P<0.01). At exon1locus, thegenotypic distribution in the Large White and Duroc populations were consistent withHardy-Weinberg equilibrium (P>0.05), whereas in the Landrace population there appeared to be genotypic disequilibrium (P<0.05). Departure from Hardy-Weinbergequilibrium was not evident for genotypes in exon2of the DRA in all breeds (P>0.05).At exon4locus, the genotypic distributions of the three pig strains were deviatedfrom Hardy-Weinberg equilibrium (P<0.05).5. Correlation analysis of polymorphisms in the SLA-DRA gene on pigletdiarrhea score showed: breed and gender had little effect (P>0.05) on piglets diarrhea,individuals with different genotypes had siginificant differences on piglet diarrhea.Individuals with genotype BC showed a higher diarrhea score in comparison to thegenotypes AA, AB, AC, CC (P<0.05) and AC showed a higher diarrhea score incomparison to the CC genotype (P<0.05) in exon1site; individuals with AA and BBwere higher than that of AC and CC (P<0.05) in exon2site; individuals with AA hada higher diarrhea score than those with genotype AB and BB in exon4site (P<0.05).These results suggested that SLA-DRA gene have influence on piglet diarrhea, andcould potentially be used as a genetic marker for selection in future pig diseaseresistance breeding programs.