Epigenetic/Genetic variations in CG-rich elements of immune-related
genes contribute to food allergy development during childhood
Abstract
Background: Genetic areas of FOXP3 TSDR, HLA-G upstream of CpG island
96, CpG41 and CpG73 islands of the HLA‐DRB1 and HLA-DQB1 genes
respectively, previously documented to display immune modulatory
properties, were subjected to epigenetic/genetic analysis to assess
their influence in IgE-mediated food allergy (FA) development in
children. Methods: 64 orally challenged and IgE- tested food allergic
subjects together with 44 controls were recruited. Targeted
pyrosequencing analysis, to detect DNA methylation status and genetic
variations was utilized and experimental results obtained were analysed
by statistical software platform and correlated to clinical data. Also,
transcription factor (TF) binding sites at study areas were unmasked by
the JASPAR prediction database. Results: Parents’ smoking was
significantly correlated with aberrant methylation patterns, regardless
food allergic or control status. HLA-G promoter region showed a trend
for hypomethylation in food allergic subjects, with one of the CG sites
displaying significantly decreased methylation values. Rs1233333,
residing within HLA-G promoter region preserved a protective role
towards DNA methylation. Variable methylation patterns were recorded for
CpG41 of the HLA‐DRB1 gene and hypermethylation of the region was
significantly correlated with the presence of (Single Nucleotide
Polymorphisms) SNPs. TFs’ recognition sites, located at studied genetic
areas and exerting pivotal regulatory biological roles, are potentially
affected from divergent DNA methylation status. Conclusions: We propose
that HLA-G expression is triggered by food derived allergens, providing
a TregFoxP3-/HLA-G+ subpopulation generation and direct
immune-tolerance. Furthermore, clear evidence is provided for the
underlying co-operation of genetic polymorphisms with epigenetic events,
mainly at CpG41 island of HLA-DRB1 gene, which need an extended
investigation and elucidation.