Isolation and characterization of MHCIIA gene from Nile tilapi a

Abstract

This study was conducted to isolate and characterize the majorhistocompatibility complex (MHC) class IIA gene from Nile tilapiaand to compare between different genotypes of this gene followinginfection with Aeromonas hydrophila. To achieve our goals PCR wasused to isolate MHC IIA gene following extraction of genomic DNAfrom fish blood and then single strand conformational polymorphism(SSCP) was used to genotype resistant and susceptible/diseased fish.The results showed 12 nucleotides deletion polymorphisms in MHCIIA with a product size of 267 bp in control and resistant fish and 255bp in susceptible/diseased fish(Glover KA, et al.2007) .Additionally ,sequences out of 50 from susceptible/diseased fish showed a nonsynonymousG23T SNP which interestingly changed the stop codonto glycin (G) amino acid with subsequent right shift to the openreading frame (ORF) . This SNP also resulted in three genotype(TT ,TG ,GG) with frequencies of 0.9,0.07 and 0.03 respectively .total protein , albumin and globulin as well as in the phagocytic. TheG23T SNP was also associated with the expression level of MHC IIAin spleen with lowest expression in susceptible/diseased fish carryingGG genotype to resistant fish (Xu T et al .,2008). Thus , SNP-diseaseresistance association analysis revealed that genotypes (GG and TG)and alleles (G) of the G23T SNP were high risk for infection