P4‐126: Genome‐wide exploration of DNA methylation in the aging brain and its relation to Alzheimer's disease

Epigenomics of Alzheimer's disease

Alzheimer's disease (AD) is a large and growing public health problem. It is characterized by the accumulation of amyloid β peptides and abnormally phosphorylated tau proteins that are associated with cognitive decline and dementia. Much has been learned about the genomics of AD from linkage analyses and, more recently, genome-wide association studies. Several but not all aspects of the genomic landscape are involved in amyloid β metabolism. The moderate concordance of disease among twins suggests other factors, potentially epigenomic factors, are related to AD. We are at the earliest stages of examining the relation of the epigenome to the clinical and pathologic phenotypes that characterize AD. Our literature review suggests that there is some evidence of age-related changes in human brain methylation. Unfortunately, studies of AD have been relatively small with limited coverage of methylation sites and microRNA, let alone other epigenomic marks. We are in the midst of 2 large studies of human brains including coverage of more than 420,000 autosomal cytosine-guanine dinucleotides with the Illumina Infinium HumanMethylation450 BeadArray, and histone acetylation with chromatin immunoprecipitation sequencing. We present descriptive data to help inform other researchers what to expect from these approaches to better design and power their studies. We then discuss future directions to inform on the epigenomic architecture of AD.

Epigenetic regulation in neurodevelopment and neurodegenerative diseases

From fertilization throughout development and until death, cellular programs in individual cells are dynamically regulated to fulfill multiple functions ranging from cell lineage specification to adaptation to internal and external stimuli. Such regulation is of major importance in brain cells, because the brain continues to develop long after birth and incorporates information from the environment across life. When compromised, these regulatory mechanisms can have detrimental consequences on neurodevelopment and lead to severe brain pathologies and neurodegenerative diseases in the adult individual. Elucidating these processes is essential to better understand their implication in disease etiology. Because they are strongly influenced by environmental factors, they have been postulated to depend on epigenetic mechanisms. This review describes recent studies that have identified epigenetic dysfunctions in the pathophysiology of several neurodevelopmental and neurodegenerative diseases. It discusses currently known pathways and molecular targets implicated in pathologies including imprinting disorders, Rett syndrome, and Alzheimer's, Parkinson's and Hungtinton's disease, and their relevance to these diseases.