Wilson disease (WD) is an autosomal recessive disorder of hepatic copper accumulation, which is caused by the dysfunction of a copper-transporting P-type ATPase that is crucial in the hepatocellular utilization and biliary excretion f copper. WD is characterized by a remarkable heterogeneity in its clinical hepatic severity and neuropsychiatric presentations. The failure to identify specific genotype-to-phenotype correlations could be due in part to the presence of epigenetic factors affecting phenotype expression. Our hypothesis is that WD phenotype and its potential response to anti copper treatment may be regulated by maternal dietary methyl group effects on offspring hepatic methionine metabolism and oxidative phosphorylation mechanisms.
Our aims will be 1) To determine the effects of maternal methyl status on hepatic genomic methylation, transcript levels of oxidative phosphorylation pathway genes and mitochondrial function of offspring and their response to copper chelation in the tx-j mouse model of WD; 2) To characterize human liver DNA methylation and plasma acyl carnitines as markers of mitochondrial function in WD patients with different phenotypic presentation. We will test the first aim in the tx-j mouse model of WD, which we have previously characterized as showing global DNA hypo-methylation and changes in the expression of genes related to hepatic methionine metabolism, genomic DNA methylation, and liver injury. We will provide control or choline supplemented diets to heterozygous dams (Atp7b +/-) and study the effects of these diets on hepatic genomic DNA methylation and gene expressions and their response to copper chelating agents in 24 week wild type and homozygous (Atp7b - /-) tx-j offspring mice with hepatic copper accumulation. In addition, we will conduct global DNA methylation studies in unstained liver biopsy slides and DNA from tissue blocks from WD patients in collaboration with medical institutions in both the United States and Europe. We will focus particularly on mitochondrial function gene expression pathways which we have shown are affected in tx-j mice liver from fetal to adult life. The proposed experiments will entail the use of epigenetic techniques including methylome analysis by MethylC- seq and pyro-sequencing in liver to determine the methylation status of CpG sites genome-wide in mice, the use of immune staining of human liver biopsy slides for global DNA methylation patterns, methylome analysis for global DNA methylation quantification, and gene specific methylation analysis, and measurements of acylcarnitines in serum/plasma samples from WD subjects as indices of mitochondrial function. The anticipated findings are that aberrant methionine metabolism and altered gene-specific DNA methylation will be prevented by maternal dietary provision of choline in mice and that WD patient with different phenotypes will have different DNA methylation and mitochondrial impairment patterns.
Epigenetic and nutritional factors may contribute to the phenotypic presentations of Wilson disease, an autosomal recessive disorder due to hepatic copper excess which can present with various hepatic manifestations. We will study the transgenerational effects of gestational supply of dietary methyl groups on offspring DNA methylation mechanisms in an animal model of Wilson Disease. Animal studies will be complemented by human studies on DNA methylation in Wilson disease patients from multiple national and international collaborating institutions.
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|Medici, Valentina; Kieffer, Dorothy A; Shibata, Noreene M et al. (2016) Wilson Disease: Epigenetic effects of choline supplementation on phenotype and clinical course in a mouse model. Epigenetics 11:804-818|