Overexpression of Gadd45b perturbs DNA methylation in mouse dopaminergic neurons

Age is a major risk factor for neurodegenerative diseases like Parkinson disease, but few studies have explored the contribution of key hallmarks of aging, namely DNA methylation changes and heterochromatin destructuration, in the neurodegenerative process. Here, we investigated the consequences of viral overexpression of Gadd45b, a multifactorial protein involved in DNA demethylation, in the mouse midbrain. Gadd45b overexpression induced global and stable changes in DNA methylation, particularly in introns of genes related to neuronal functions, as well as on LINE-1 transposable elements. This was paralleled by disorganized heterochromatin, increased DNA damage and vulnerability to oxidative stress. LINE-1 de-repression, a potential source of DNA damage, preceded Gadd45b-induced neurodegeneration, whereas prolonged Gadd45b expression deregulated expression of genes related to heterochromatin maintenance, DNA methylation or Parkinson disease. Our data indicates that aging-related alterations contribute to dopaminergic neuron degeneration with potential implications for Parkinson disease. Overall design: Examination of DNA methylation changes upon injection of a virus encoding Gadd45b compared tio a virus encoding mCherry as. a control into the mouse substantia nigra. DNA extraction after 14 and 90 days. RRBS-sequencing was perfomed in single-end mode, generating 50 bases reads (SE50) on an Illumina HiSeq 3000