Dataset Information

Effects of aging on circadian patterns of gene expression in the human prefrontal cortex.

ABSTRACT: With aging, significant changes in circadian rhythms occur, including a shift in phase toward a "morning" chronotype and a loss of rhythmicity in circulating hormones. However, the effects of aging on molecular rhythms in the human brain have remained elusive. Here, we used a previously described time-of-death analysis to identify transcripts throughout the genome that have a significant circadian rhythm in expression in the human prefrontal cortex [Brodmann's area 11 (BA11) and BA47]. Expression levels were determined by microarray analysis in 146 individuals. Rhythmicity in expression was found in ? 10% of detected transcripts (P < 0.05). Using a metaanalysis across the two brain areas, we identified a core set of 235 genes (q < 0.05) with significant circadian rhythms of expression. These 235 genes showed 92% concordance in the phase of expression between the two areas. In addition to the canonical core circadian genes, a number of other genes were found to exhibit rhythmic expression in the brain. Notably, we identified more than 1,000 genes (1,186 in BA11; 1,591 in BA47) that exhibited age-dependent rhythmicity or alterations in rhythmicity patterns with aging. Interestingly, a set of transcripts gained rhythmicity in older individuals, which may represent a compensatory mechanism due to a loss of canonical clock function. Thus, we confirm that rhythmic gene expression can be reliably measured in human brain and identified for the first time (to our knowledge) significant changes in molecular rhythms with aging that may contribute to altered cognition, sleep, and mood in later life.

SUBMITTER: Chen CY

PROVIDER: S-EPMC4711850 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Effects of aging on circadian patterns of gene expression in the human prefrontal cortex.

Chen Cho-Yi CY Logan Ryan W RW Ma Tianzhou T Lewis David A DA Tseng George C GC Sibille Etienne E McClung Colleen A CA

Proceedings of the National Academy of Sciences of the United States of America 20151222 1

With aging, significant changes in circadian rhythms occur, including a shift in phase toward a "morning" chronotype and a loss of rhythmicity in circulating hormones. However, the effects of aging on molecular rhythms in the human brain have remained elusive. Here, we used a previously described time-of-death analysis to identify transcripts throughout the genome that have a significant circadian rhythm in expression in the human prefrontal cortex [Brodmann's area 11 (BA11) and BA47]. Expressio ...[more]

PMID: 26699485

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Project description:With aging, significant changes in circadian rhythms occur, including a shift in phase toward a âmorningâ chronotype and a loss of rhythmicity in circulating hormones. However, the effects of aging on molecular rhythms in the human brain have remained elusive. Here we employed a previously-described time-of-death analyses to identify transcripts throughout the genome that have a significant circadian rhythm in expression in the human prefrontal cortex (Brodmannâs areas (BA) 11 and 47). Expression levels were determined by microarray analysis in 146 individuals. Rhythmicity in expression was found in ~10% of detected transcripts (p<0.05). Using a meta-analysis across the two brain areas, we identified a core set of 235 genes (q<0.05) with significant circadian rhythms of expression. These 235 genes showed 92% concordance in the phase of expression between the two areas. In addition to the canonical core circadian genes, a number of other genes were found to exhibit rhythmic expression in the brain. Notably, we identified more than one thousand genes (1186 in BA11; 1591 in BA47) that exhibited age-dependent rhythmicity or alterations in rhythmicity patterns with aging. Interestingly, a set of transcripts gained rhythmicity in older individuals, which may represent a compensatory mechanism due to a loss of canonical clock function. Thus, we confirm that rhythmic gene expression can be reliably measured in human brain and identified for the first time significant changes in molecular rhythms with aging that may contribute to altered cognition, sleep and mood in later life. Using the resources of the University of Pittsburghâs Brain Tissue Donation Program, 210 subjects were identified. Samples were obtained after consent from next-of-kin during autopsies conducted at the Allegheny County Medical Examinerâs Office (Pittsburgh, USA). The absence of lifetime psychiatric disorders was determined by an independent committee of experienced clinical research scientists using information from clinical records, toxicology results and a standardized psychological autopsy. Subjects of unwitnessed death were removed from the study. A total of 146 individuals with the following characteristics were analyzed in this study: mean (range) age of 50.7 (16-96) years, 78% male, 85% Caucasian, mean postmortem interval (PMI) for brain collection 17.3 (4.8-28) hours, mean pH 6.7 (5.8-7.6) and RNA integrity number (RIN) 8.0 (5.9-9.6). For each subject, the right hemisphere was blocked coronally, frozen and stored at -80C. Blocks containing Brodmann area 11 (BA11) or Brodmann area 47 (BA47) of the orbital PFC were cut on a cryostat, and cortical gray matter was collected for RNA extraction as previously described. All procedures were approved by the University of Pittsburghâs Institutional Review Board for Biomedical Research and Committee for Research Involving the Dead.

Project description:BACKGROUND:Age changes in expression of inflammatory, synaptic, and neurotrophic genes are not well characterized during human brain development and senescence. Knowing these changes may elucidate structural, metabolic, and functional brain processes over the lifespan, as well vulnerability to neurodevelopmental or neurodegenerative diseases. HYPOTHESIS:Expression levels of inflammatory, synaptic, and neurotrophic genes in the human brain are coordinated over the lifespan and underlie changes in phenotypic networks or cascades. METHODS:We used a large-scale microarray dataset from human prefrontal cortex, BrainCloud, to quantify age changes over the lifespan, divided into Development (0 to 21 years, 87 brains) and Aging (22 to 78 years, 144 brains) intervals, in transcription levels of 39 genes. RESULTS:Gene expression levels followed different trajectories over the lifespan. Many changes were intercorrelated within three similar groups or clusters of genes during both Development and Aging, despite different roles of the gene products in the two intervals. During Development, changes were related to reported neuronal loss, dendritic growth and pruning, and microglial events; TLR4, IL1R1, NFKB1, MOBP, PLA2G4A, and PTGS2 expression increased in the first years of life, while expression of synaptic genes GAP43 and DBN1 decreased, before reaching plateaus. During Aging, expression was upregulated for potentially pro-inflammatory genes such as NFKB1, TRAF6, TLR4, IL1R1, TSPO, and GFAP, but downregulated for neurotrophic and synaptic integrity genes such as BDNF, NGF, PDGFA, SYN, and DBN1. CONCLUSIONS:Coordinated changes in gene transcription cascades underlie changes in synaptic, neurotrophic, and inflammatory phenotypic networks during brain Development and Aging. Early postnatal expression changes relate to neuronal, glial, and myelin growth and synaptic pruning events, while late Aging is associated with pro-inflammatory and synaptic loss changes. Thus, comparable transcriptional regulatory networks that operate throughout the lifespan underlie different phenotypic processes during Aging compared to Development.

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Dataset Information

Effects of aging on circadian patterns of gene expression in the human prefrontal cortex.

Publications

Effects of aging on circadian patterns of gene expression in the human prefrontal cortex.

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