Age-associated methylation change of TAP1 promoter in piglet

Diarrhea and edematous disease are two major causes of mortality in postweaning piglets. These conditions lead to huge economic losses in the swine industry. Escherichia coli F18 is the primary causative agent of these two diseases. Transported associated with antigen processing (TAP) plays an important role in the immune response and the TAP1 gene could be an effective anti-E. coli F18 molecular marker in pigs. The aim of this study was to determine the correlation between TAP1 gene promoter CpG island methylation status and mRNA expression in piglets. In this study, bisulfite sequencing PCR (BSP) was used to detect the methylation status of the TAP1 gene promoter CpG islands and fluorescence quantitative PCR was used to detect TAP1 expression in the jejunum of Sutai piglets from birth to weaning age. The fragment of the TAP1 gene promoter region under investigation has no mutation, has 13 putative transcription factor binding sites containing 19 CpG sites, and may be important for regulation of gene expression. With increasing age, the overall methylation levels decreased, while the TAP1 expression levels increased, indicating a negative correlation between TAP1 expression and promoter methylation levels. Variance analysis showed significant differences in the methylation status of CpG_4, CpG_13 and CpG_15 among the different age groups (P<0.05). Our data indicate that TAP1 expression is increased by demethylation of promoter CpG islands, with CpG_4, CpG_13 and CpG_15 implicated as the critical regulatory sites.