Chicken endogenous viruses, ALVE (Avian Leukosis Virus subgroup E), are inherited as LTR (long terminal repeat) retrotransposons, which are negatively correlated with disease resistance, and any changes in DNA methylation may contribute to the susceptibility to neoplastic disease. The relationship between ALVE methylation status and neoplastic disease in the chicken is undefined. White Leghorn inbred lines 7₂ and 6₃ at the ADOL have been respectively selected for resistance and susceptibility to tumors that are induced by avian viruses. In this study, the DNA methylation patterns of 3∼6 CpG sites of four conserved regions in ALVE, including one unique region in ALVE1, the promoter region in the TVB (tumor virus receptor of ALV subgroup B, D and E) locus, were analyzed in the two lines using pyrosequencing methods in four tissues, i.e., liver, spleen, blood and hypothalamus. A significant CpG hypermethylation level was seen in line 7₂ in all four tissues, e.g., 91.86±1.63% for ALVE region2 in blood, whereas the same region was hemimethylated (46.16±2.56%) in line 6₃. CpG methylation contents of the ALVE regions were significantly lower in line 6₃ than in line 7₂ in all tissues (P<0.01) except the ALVE region 3/4 in liver. RNA expressions of ALVE regions 2 and 3 (PPT-U3) were significantly higher in line 6₃ than in line 7₂ (P<0.01). The methylation levels of six recombinant congenic strains (RCSs) closely resembled to the background line 6₃ in ALVE-region 2, which imply the methylation pattern of ALVE-region 2 may be a biomarker in resistant disease breeding. The methylation level of the promoter region in the TVB was significantly different in blood (P<0.05) and hypothalamus (P<0.0001), respectively. Our data disclosed a hypermethylation pattern of ALVE that may be relevant for resistance against ALV induced tumors in chickens.

Publications with shared reference:

0 publications found