Whole genome methylation sequencing in blood identifies extensive differential DNA methylation in late-onset dementia due to Alzheimer's disease

INTRODUCTION

DNA microarray-based studies report differentially methylated positions (DMPs) in blood between late-onset dementia due to Alzheimer's disease (AD) and cognitively unimpaired individuals, but interrogate < 4% of the genome.

METHODS

We used whole genome methylation sequencing (WGMS) to quantify DNA methylation levels at 25,409,826 CpG loci in 281 blood samples from 108 AD and 173 cognitively unimpaired individuals.

RESULTS

WGMS identified 28,038 DMPs throughout the human methylome, including 2707 differentially methylated genes (e.g., SORCS3, GABA, and PICALM) encoding proteins in biological pathways relevant to AD such as synaptic membrane, cation channel complex, and glutamatergic synapse. One hundred seventy-three differentially methylated blood-specific enhancers interact with the promoters of 95 genes that are differentially expressed in blood from persons with and without AD.

DISCUSSION

WGMS identifies differentially methylated CpGs in known and newly detected genes and enhancers in blood from persons with and without AD.

HIGHLIGHTS

Whole genome DNA methylation levels were quantified in blood from persons with and without Alzheimer's disease (AD). Twenty-eight thousand thirty-eight differentially methylated positions (DMPs) were identified. Two thousand seven hundred seven genes comprise DMPs. Forty-eight of 75 independent genetic risk loci for AD have DMPs. One thousand five hundred sixty-eight blood-specific enhancers comprise DMPs, 173 of which interact with the promoters of 95 genes that are differentially expressed in blood from persons with and without AD.

Adolescent treatment. Implications for assessment, practice guidelines, and outcome management

Treatment for adolescent substance abuse does work. Not only are there clear improvements in substance use frequency and in the number of substances used 1 year after treatment, but also sharp reductions in school and legal problems are observed. Improvements in treatment and the continuum of care can be made however. Substance abuse treatment cannot end with the formal treatment episode. Continuing attendance at support groups, family support, and proactive re-entry plans at school all help to ensure continued recovery after treatment. Many adolescents receive a large amount of medical care in the year prior to admission; however, very few adolescents or their parents list physicians as referral sources at admission. Adolescent substance abuse should be identified by physicians and thereby treated sooner. Through the use of a three-item screen, physicians can reliably identify high-risk adolescents and confidently refer them for a formal chemical dependency evaluation. The use of FIRM has provided a means of understanding how the interactions of certain pretreatment characteristics best predict treatment outcome. Based on such analyses, patient needs can be identified, and practice guidelines can be empirically derived through an iterative process of implementation and evaluation. As the variability of treatment elements increases, treatment process data will become richer. This trend will enable providers to further refine the patient-treatment match by determining the amounts of exposure to specific treatment elements that are most predictive of a positive outcome for a particular group of patients. Efforts have been made to classify chemically dependent patients through the use of factor and cluster analytic techniques. By first identifying discrete types of patients and then measuring how the many services in the treatment experience interact to produce favorable outcomes, optimal treatment guidelines could potentially be derived for each patient type. Further research in this area would further strengthen the bridge between the domains of clinical assessment, practice guidelines, and treatment outcome, setting the stage for even more effective patient-treatment matching and improved outcomes.