Brain areas involved with obsessive-compulsive disorder present different DNA methylation modulation.

BACKGROUND: Obsessive-compulsive disorder (OCD) is characterized by intrusive thoughts and repetitive actions, that presents the involvement of the cortico-striatal areas. The contribution of environmental risk factors to OCD development suggests that epigenetic mechanisms may contribute to its pathophysiology. DNA methylation changes and gene expression were evaluated in post-mortem brain tissues of the cortical (anterior cingulate gyrus and orbitofrontal cortex) and ventral striatum (nucleus accumbens, caudate nucleus and putamen) areas from eight OCD patients and eight matched controls. RESULTS: There were no differentially methylated CpG (cytosine-phosphate-guanine) sites (DMSs) in any brain area, nevertheless gene modules generated from CpG sites and protein-protein-interaction (PPI) showed enriched gene modules for all brain areas between OCD cases and controls. All brain areas but nucleus accumbens presented a predominantly hypomethylation pattern for the differentially methylated regions (DMRs). Although there were common transcriptional factors that targeted these DMRs, their targeted differentially expressed genes were different among all brain areas. The protein-protein interaction network based on methylation and gene expression data reported that all brain areas were enriched for G-protein signaling pathway, immune response, apoptosis and synapse biological processes but each brain area also presented enrichment of specific signaling pathways. Finally, OCD patients and controls did not present significant DNA methylation age differences. CONCLUSIONS: DNA methylation changes in brain areas involved with OCD, especially those involved with genes related to synaptic plasticity and the immune system could mediate the action of genetic and environmental factors associated with OCD.

Layer-specific reduced neuronal density in the orbitofrontal cortex of older adults with obsessive-compulsive disorder.

Neurobiological models have provided consistent evidence of the involvement of cortical-subcortical circuitry in obsessive-compulsive disorder (OCD). The orbitofrontal cortex (OFC), involved in motivation and emotional responses, is an important regulatory node within this circuitry. However, OFC abnormalities at the cellular level have so far not been studied. To address this question, we have recruited a total of seven senior individuals from the Sao Paulo Autopsy Services who were diagnosed with OCD after an extensive post-mortem clinical evaluation with their next of kin. Patients with cognitive impairment were excluded. The OCD cases were age- and sex-matched with 7 control cases and a total of 14 formalin-fixed, serially cut, and gallocyanin-stained hemispheres (7 subjects with OCD and 7 controls) were analyzed stereologically. We estimated laminar neuronal density, volume of the anteromedial (AM), medial orbitofrontal (MO), and anterolateral (AL) areas of the OFC. We found statistically significant layer- and region-specific lower neuron densities in our OCD cases that added to a deficit of 25% in AM and AL and to a deficit of 21% in MO, respectively. The volumes of the OFC areas were similar between the OCD and control groups. These results provide evidence of complex layer and region-specific neuronal deficits/loss in old OCD cases which could have a considerable impact on information processing within orbitofrontal regions and with afferent and efferent targets.

Initial findings of striatum tripartite model in OCD brain samples based on transcriptome analysis.

Obsessive-compulsive disorder (OCD) is a psychiatric disorder characterized by obsessions and/or compulsions. Different striatal subregions belonging to the cortico-striato-thalamic circuitry (CSTC) play an important role in the pathophysiology of OCD. The transcriptomes of 3 separate striatal areas (putamen (PT), caudate nucleus (CN) and accumbens nucleus (NAC)) from postmortem brain tissue were compared between 6 OCD and 8 control cases. In addition to network connectivity deregulation, different biological processes are specific to each striatum region according to the tripartite model of the striatum and contribute in various ways to OCD pathophysiology. Specifically, regulation of neurotransmitter levels and presynaptic processes involved in chemical synaptic transmission were shared between NAC and PT. The Gene Ontology terms cellular response to chemical stimulus, response to external stimulus, response to organic substance, regulation of synaptic plasticity, and modulation of synaptic transmission were shared between CN and PT. Most genes harboring common and/or rare variants previously associated with OCD that were differentially expressed or part of a least preserved coexpression module in our study also suggest striatum subregion specificity. At the transcriptional level, our study supports differences in the 3 circuit CSTC model associated with OCD.