Epigenetics and trauma

Transcription

1 Epigenetics and trauma Influence of trauma on mental health Patrick McGowan, PhD Biological Sciences, UTSC Cell and Systems Biology, Psychology University of Toronto Leuven, November, 2012 Plasticity Stress response Fearfulness Neuroplasticity Stress response Anxiety/Depression Substance abuse Suicide Life course Environmental challenges after Hanson et al., Prog Biophys Mol Bio, 2011 In search of a unifying principle in complex disease research A dynamic neural epigenome Petronis, TIGS, 2006 Is epigenetic signaling altered in suicide and childhood abuse? Suicide: Mitigating factors Tissue: Postmortem hippocampus Groups: Suicides: Males with a history of childhood abuse/neglect. Controls: Males who died suddenly of other causes (heart attack, car accident). A leading cause of death worldwide. Linked to, but not predicted by mental disorders and life events. Genetic and nongenetic factors contribute. Changes in gene expression in the brain associate with suicide. McGowan et al., PLoS ONE,

2 Ribosomal RNA (rrna) is a bottleneck for protein production in the cell DNA methylation ACTCGATGTA active gene There are many copies (400+) of this gene in the genome. hippocampal volume and neurogenesis in Major Depression, suggesting protein production is impaired. environment diet toxins/infection social CH 3 ACTCGATGTA inactive gene Ribosomal RNA (rrna) is a bottleneck for protein production in the cell The rrna promoter is hypermethylated in the hippocampus of suicide victims rrna activity in the hippocampus in Alzheimer Disease. 45S rrna expression determined by DNA methylation of the promoter region. Gene body Suicide: increased methylation and reduced expression of rrna gene in hippocampus No DNA sequence changes in the rrna promoter among subjects 2

3 Mean Methylation Differential methylation of rrna is brain region and locus specific A ** B rrna promoter is hypermethylated and expression reduced in the hippocampus of suicide victims. C Because all suicide victims were abused, the data suggest the effects are due to childhood abuse, the mental illness associated with suicide or both. The brain s stress response system Y Y Y Y Hippocampus GR receptors Negative Feedback Behavioural programming of gene activity H Hypothalamus P A CRH Pituitary ACTH Adrenal Cortex In rats, maternal care = Licking and Grooming (LG). CORT Natural variations in maternal care Behavioural programming of DNA methylation in the hippocampus EMBRYO DAY 20 LOW LG HIGH LG BIRTH DAY 1 Weaver et al. Nature Neurosci (2004) GR1 7 PROMOTER * * PUP DAY 6 Age WEANING DAY 21 * ADULT DAY 90 3

4 Are the epigenetic effects a result of maternal care? Anxiety in the rat: Open Field Testing Video Camera INNER FIELD Champagne et al., Science 1999; Weaver et al., Nature Neurosci, 2004 (a) Methyl Donors Reverse Anxiety Behaviour of Adult Offspring of HIGHLG Mothers (b) Vehicle TSA Methionine * Low LGABN Maternal care ** High LGABN Vehicle TSA Methionine Low LGABN Maternal care High LGABN Does child abuse mark the Glucocorticoid Receptor (GR) gene in the hippocampus? Epigenetic regulation by maternal care in adult rats (Weaver et al., 2004). Childhood adversity: alters stress response and increases suicide risk later in life. Groups: Suicides: Abused in childhood Suicides: Nonabused Controls: Died of causes other than suicide. McGowan et al., Nature Neuroscience (2009) Epigenetic regulation of Glucocorticoid Receptor (GR) in human brain Abusespecific DNA methylation of GR Expression Methylation McGowan et al. Nature Neuroscience (2009) 4

5 2000bp TSS First exon Exon Last exon TES +2000bp 2000bp TSS First exon Exon Last exon TES +2000bp 2000bp TSS First exon Exon Last exon TES +2000bp log(h) log(l) GR promoter is hypermethylated and expression reduced in the hippocampus of suicide victims with a history of childhood abuse. What is the epigenomic response to early adversity? The data suggest that childhood abuse confers additional risk for suicide through epigenetic changes involved in the stress response. Tiling epigenomic microarray A broad epigenomic response to early environment 7,000,000 base pairs CpG Islands H3K9 Acetylation DNA Methylation mrna Expression Genes PCDH clusters Glucocorticoid Receptor Tiling microarray: A method for study of gene regulation and gene discovery. Broad changes in DNA methylation A broad epigenomic response to early environment Gene body a Protocadherin gene family: Regulation by maternal care H3K9 Acetylation DNA Methylation mrna EXP c H3K9 Acetylation DNA Methylation RNA Expression PCDH alpha b H3K9 Acetylation DNA Methylation mrna EXP PCDH beta Correspondence between epigenetic and transcriptional regulation McGowan et al., PLoS ONE

6 Hippocampal neuroplasticity: Influence of maternal care A broad epigenomic response to early environment % 5meC 5meC Controls Abused PCDH Glucocorticoid receptor Gene desert Champagne et al.,2008; Bagot et al., 2009 Suderman*, McGowan* et al. PNAS (2012) A broad epigenomic response in suicide Summary of epigenomic studies 100% % 5meC 0% 5meC Controls Abused Epigenetic changes occur across wide regions of the genome in response to early life events, including adversity. The differences in epigenetic signaling greatest in gene bodies not promoters. The changes are nonrandom and patterned, suggesting Programming by environmental events. Influence of trauma on mental health Early life Mental Health The Comprehensive Phenotype Stress response Fearfulness Neuroplasticity Stress response Anxiety/Depression Substance abuse Suicide Epigenome Phenotype Gene Expression Programming Establishment during development Maintenance during cell division 6

7 How to study environmental epigenetics in living humans Bidirectional communication Hippocampus Accessible Peripheral Tissue: Hypothalamus Immune System Negative Feedback CRH Pituitary ACTH Adrenal Cortex CORT Direct: bloodbrain barrier Stimulation of second messenger Stimulation of vagus nerve Immune System Central Nervous System Hormones Immune factors Neurotransmitters The nervous system communicates with the immune system GR methylation in newborns reflects maternal mood Mental Disorders Central Nervous System Immune factors: IFNy TNFa/b IL2/4/6/10/12 Hormones: ACTH Glucocorticoids Catecholamines Mineralcorticoids Neurotransmitters: Serotonin Dopamine Gaba NGF N 2 = N 2 = N 2 = White blood cells: Altered gene function Oberlander et al., Epigenetics (2008) GR methylation in newborns reflects maternal mood Developmental origins of phenotypes Environmental Exposure Epigenomic Variation Environmental Exposure Stress response at 3 months of age correlates with GR methylation at birth. Prenatal effects on GR methylation may predict health outcomes later on. Oberlander et al., Epigenetics (2008) Environmental Exposure Genomic Variation Environmental Exposure 7

8 Acknowledgements Biological Sciences McGowan Lab: Aya Sasaki Pauline Pan Sophie StCyr Sophia Lavergne Amy Newman Wilfred de Vega Psychiatry Pharmacology & Therapeutics Michael Meaney Lab Moshe Szyf Lab Gustavo Turecki Lab 8