Background: Psychosis is a debilitating syndrome occurring in 40-60% of people with Alzheimer’s disease (AD) and corresponds with a more severe disease course. Evidence suggests that psychosis in AD (AD+P) is associated with a distinct profile of neurobiological changes, but little is known about the molecular processes driving etiology. In this study we performed an epigenome-wide association study (EWAS) to investigate DNA methylation associated with AD+P in the dorsolateral prefrontal cortex of 192 post-mortem brain samples.
Method: Brain samples with corresponding in life neuropsychiatric assessments were obtained from the University of Pittsburgh Alzheimer’s disease Research Center (PITT-ADRC). AD pathology was assessed and classified using CERAD neuritic plaque density score, Braak neurofibrillary tangle stages and NIA-RI criteria. The presence or absence of delusions and hallucinations was scored on the CERAD Behavioral Rating Scale. DNA was extracted, bisulfite treated and then profiled on the Illumina Methylation EPIC Array.
Result: After data processing and quality control we used linear regression models to compare 152 AD+P samples to 40 AD samples without psychosis (AD-P). A regional analysis of spatially correlated p-values highlighted four differentially methylated regions (DMRs) associated with psychosis, which are being replicated in other data sets and validated for cell specificity using fluorescence activated nuclei sorting (FANS).
Conclusion: The development of effective therapies for AD+P is an urgent priority. To address this we have collated a well powered study cohort to interrogate the epigenetic basis of AD+P, finding significant methylomic variation. This variation provides an insight into potential mechanisms and biomarkers which will help to identify drug targets and enable better treatment with existing medications.
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