GSE117592
Epigenetic changes of the thioredoxin system in the tx-j mouse model and in patients with Wilson disease
Wilson disease (WD) is caused by mutations in the copper transporter ATP7B, leading to copper accumulation in the liver and brain. Excess copper inhibits S-adenosyl-L-homocysteine hydrolase, leading to variable WD phenotypes from widespread alterations in DNA methylation and gene expression. Previously, we demonstrated that maternal choline supplementation in the Jackson toxic milk (tx-j) mouse model of WD corrected higher thioredoxin 1 transcript levels in fetal liver. Here, we investigated the effect of maternal choline supplementation on genome-wide DNA methylation patterns in tx-j fetal liver by whole-genome bisulfite sequencing (WGBS). Tx-j Atp7b genotype-dependent differences in DNA methylation were corrected by choline for genes including, but not exclusive to, oxidative stress pathways. To examine phenotypic effects of postnatal choline supplementation, tx-j mice were randomized to one of six treatment groups: with or without maternal and/or continued choline supplementation, and with or without copper chelation with penicillamine (PCA) treatment. Hepatic transcript levels of thioredoxin 1 and peroxiredoxin 1 were significantly higher in mice receiving maternal and continued choline with or without PCA treatment compared to untreated mice.  A comparison of WGBS of human WD liver compared to tx-j mouse liver demonstrated a significant overlap of differentially-methylated genes associated with ATP7B deficiency. Further, eight genes in the thioredoxin pathway were differentially methylated in human WD liver samples. In summary, Atp7b deficiency and choline supplementation have a genome-wide impact, including on thioredoxin system-related genes, in tx-j mice. These findings could explain the variability of WD phenotype and suggest new complementary treatment options for WD. Overall design: Investigation of DNA methylation with whole-genome bisulfite sequencing (WGBS) in liver from tx-j and C3H mice at E17, with and without maternal choline supplementation. Tx-j mice carry a homozygous Gly712Asp missense mutation in Atp7b. Dams were fed normal or high choline diet for 2 weeks before mating and through gestation. Tx-j pups were fostered by C3H dam with sam diet that gave birth on the same day. Fetal livers of pups from the same litter were pooled. Pooled liver samples: C3H + control diet (n=4), C3H + choline diet (n=4), tx-j + control diet (n=4), tx-j + choline diet (n=4)