The transduction of cellular signals occurs through the modification of target molecules. Most of these modifications are transitory, thus the signal transduction pathways can be tightly regulated. Reactive nitrogen species are a group of compounds with different properties and reactivity. Some reactive nitrogen species are highly reactive and their interaction with macromolecules can lead to permanent modifications, which suggested they were lacking the specificity needed to participate in cell signaling events. However, the perception of reactive nitrogen species as oxidizers of macromolecules leading to general oxidative damage has recently evolved. The concept of redox signaling is now well established for a number of reactive oxygen and nitrogen species. In this context, the post-translational modifications introduced by reactive nitrogen species can be very specific and are active participants in signal transduction pathways. This review addresses the role of these oxidative modifications in the regulation of cell signaling events.

Epigenetic deregulation of α‐synuclein plays a key role in Parkinson’s disease (PD). Analysis of the SNCA promoter using the ENCODE database revealed the presence of important histone post‐translational modifications (PTMs) including transcription‐promoting marks, H3K4me3 and H3K27ac, and repressive mark, H3K27me3. We investigated these histone marks in post‐mortem brains of controls and PD patients and observed that only H3K4me3 was significantly elevated at the SNCA promoter of the substantia nigra (SN) of PD patients both in punch biopsy and in NeuN‐positive neuronal nuclei samples. To understand the importance of H3K4me3 in regulation of α‐synuclein, we developed CRISPR/dCas9‐based locus‐specific H3K4me3 demethylating system where the catalytic domain of JARID1A was recruited to the SNCA promoter. This CRISPR/dCas9 SunTag‐JARID1A significantly reduced H3K4me3 at SNCA promoter and concomitantly decreased α‐synuclein both in the neuronal cell line SH‐SY5Y and idiopathic PD‐iPSC derived dopaminergic neurons. In sum, this study indicates that α‐synuclein expression in PD is controlled by SNCA’s histone PTMs and modulation of the histone landscape of SNCA can reduce α‐synuclein expression.

Age is the primary risk factor for Parkinson's disease (PD), but how aging changes the expression and regulatory landscape of the brain remains unclear. Here, we present a single-nuclei multiomic study profiling shared gene expression and chromatin accessibility of young, aged and PD post-mortem midbrain samples. Combined multiomic analysis of midbrain nuclei along a pseudopathogenesis trajectory reveals all glial cell types are affected by age, but microglia and oligodendrocytes are further altered in PD. We present evidence for a novel age-associated oligodendrocyte subtype that appears during normal aging, characterized by elevated protein folding and chaperone-mediated autophagy pathways. Differential gene and protein-protein interaction analyses show that these functions are significantly compromised in PD. Peak-gene association from our paired data identifies differential cis-elements linked to regulation of differentially expressed genes between PD patients and neurologically healthy controls. Our study suggests a previously undescribed role for oligodendrocytes in aging and PD pathogenesis.