Correlation Studies Between Methylation Of RLRs And Resistance/Susceptibility To GCRV In Grass Carp(Ctenopharyngodon Idella)

Grass carp(Ctenopharyngodon idella) is an important freshwater economic aquaculture species in China, while the development of breeding industry has been severely limited by the diversiform bacterial and viral diseases, of which hemorragic disease of grass carp causes the most serious hazard triggered by the grass carp reovirus(GCRV). Antiviral defense primarily depends on innate immunity system in teleosts, and the identification of pattern recognition receptor(PRR) to the invasive pathogenic microorganism constitutes the first defensive line of innate immunity. RIG-I-like receptors(RLRs), which is a class of intracellular PRRs involving laboratory of genetics and physiology 2, melanoma differentiation associated gene 5 and retinoic acid induced gene-I, are initially characterized as a dsRNA-binding protein and transferring the signaling to the adaptor, triggering interferon(IFN) and proinflammatory cytokines induction in response to virus invasion.The transcription of Ctenopharyngodon idella LGP2, MDA5 and RIG-I(CiLGP2, Ci MDA5,CiRIG-I) up-regulated post GCRV stimulation manifested that RLRs might participate in the antiviral immunity response against GCRV, while the regulatory machenism of RLRs antivial expression remains unclear.The present study carried on the correlation studies between methylation and mRNA expression of RLRs as well as the difference analysis on methylation between the susceptible and resistant group post GCRV infection. The obtained results are as follows:1. The methylation levels of-1411 CpG site in CiLGP2, possessing the diversform methylation patterns, were significantly lower in spleen than in muscle. While CiLGP2 expression was higher in spleen than in muscle on the contrary;2. There was no significantly different methylated CpG site between the susceptible and resistant group in CiLGP2;3. The methylation levels of +200, +202, +204 and +207 CpA/CpG sites in CiMDA5 were significantly higher in the susceptible group than in the resistant one;4. mRNA expression of CiMDA5 was significantly lower in the susceptible group than in the resistant one;5. The methylation levels of-534 CpG site in CiRIG-I were significantly higher in the susceptible group than in the resistant one;6. mRNA expression of CiRIG-I was significantly lower in the susceptible group than in the resistant one;7. Both CiLGP2 and CiRIG-I were detected the spontaneous deamination phenomenon in 5’-flanking region.In conclusion, the antiviral expression of RLRs’ members might be nagetively regulated by DNA methylation. What’s more, the methylation of densely methylated element(DME) in CiMDA5 and-534 CpG site in CiRIG-I were significantly related to the resistance of hemorragic disease of grass carp.This research revealed the antiviral regulatory mechanism of RLRs from the perspective of epigenetics in grass carp and obtained a series of methylated sites significantly related to the resistance against GCRV which could be served as the molecular markers of hemorragic disease of grass carp and provide a novel viewpoint for the disease-resistant selection of strains in grass carp.