Presentation on theme: "Gene-Environment Interplay on Behaviour Marla B. Sokolowski, PhD, FRSC University Professor Canada Research Chair in Genetics and Behavioural Neurology,"— Presentation transcript:
Gene-Environment Interplay on Behaviour Marla B. Sokolowski, PhD, FRSC University Professor Canada Research Chair in Genetics and Behavioural Neurology, Academic Director Institute for the Fraser Mustard Human Development. Co-director of Canadian Institutes for Advanced Research (CIFAR) Experience Based Brain and Biological Development Programme (EBBD),
Early adversity sets developmental trajectories for health, learning and social functioning across the life-time. How? a) Gene-Environment Interactions b) Epigenetics
For most traits: It’s not just nature (genes) It’s not just nurture (environment) It’s not nature plus nature (genes + environment). It is their interaction! G x E Sokolowski and Wahlsten 2001
Example of Gene by Environment Interaction in Human Mothering Behavior (serotonin transporter gene variants LL, SS and LS) Mileva-Seitz et al 2011
Why? Conservation of DNA Sequence Conservation of a Gene’s Behavioural Function Candidate Genes Model Organisms to Humans
Almost all organisms have the gene including humans! The gene affects energy balance: food intake, food related movement, fat, learning and memory Different individuals have different forms of the gene –rover or sitter The gene makes an enzyme found in the brain called PKG. Rovers have more of it than sitters How much enzyme the gene makes depends on the environment. (G x E) Example 2: G x E: The foraging (for) gene (Osborne et al 1997 Science; Ben Shahar et al 2002 Science; Mery et al 2007 PNAS; Fitzpatrick et al 2007 Nature; Kaun et al 2007 J Exp Biol; Lucas and Sokolowski 2009 PNAS; Sokolowski 2010 Neuron).
The rover/sitter natural variants are due to variation in a single gene called foraging which makes a cGMP-dependent protein kinase (PKG) enzyme Rover heads and larval CNSs have more foraging enzyme than sitter heads and larval CNSs. Osborne et al. 1997 Science 277: 834-836.
Proof of cloning the DNA of the foraging gene: “Gene Therapy”
Honey Bee Ant Forager or defender Nematode Worm Roamer or dweller Nurse or forager Fruit Flies Rover or sitter The foraging gene responds to the environment BenShahar et al 2002 Science Lucas & Sokolowski 2009 PNAS Fujiwara et al. 2002 Neuron Osborne et al 1997 Science Sokolowski 2010 Neuron
Gene-Environment Interaction in response to the nutritional environment
Example 2: Rovers change into sitters when chronically food deprived (the gene is responsive to the early rearing environment) Food Intake 5 10 15 100%15% * Food Quality Rover Sitter Enzyme Activity 4 8 12 100%15% Food Quality Rover Sitter Kaun et al 2007 J Exp Biol
Chronic nutritional deprivation in the larval period affects adult exploratory behaviour Burns et al 2012 PNAS
High ‘darting exploration’ Low ‘darting exploration’ Darting Exploration (darting is stop and go motion)
Burns et 2012 PNS G-E interplay: sitter adults exhibit a more plastic response to modifications in the larval nutritional environment *** p<0.001 ***
www.chickencrap.com Cost of darting exploration Dworkin, Michigan State
*** *** p<0.001, ** p<0.01, * p<0.05 Increasing foraging gene expression in the mushroom bodies changes exploratory behavior from sitter to rover (reared in 100% food) Burns et al 2012 PNAS UAS-forT1a + - + - + - - Gal4 30Y 201Y 739Y None
Chronic food deprivation early in life effects adult fitness (fecundity) Burns et al 2012 PNAS
foraging affects learning and memory: the gene is responsive to the environment Rovers have better short term memory. foraging acts in the mushroom bodies for olfactory based aversive learning and memory Mery et al 2007 PNAS
Example 3: Gene-Environment interplay in response to social context
STM: s itters are sensitive to the learning context (rovers and sitters are trained alone or in groups) P = 0.20 P = 0.005 Kohn, Reaume, Burns, Sokolowski, Mery (submitted)
Increasing foraging enables sitter to learn when alone PKG activator (8-Bromo-cGMP) on flies trained and tested alone Treatment S2S2 P = 0.01 P < 0.001
S2S2 Treatment P = 0.01 Decreasing PKG decreases learning in rovers PKG inhibitor (KT5823) on individuals trained and tested alone
Early adversity sets developmental trajectories for health and behaviour across the life-time. How? a) Gene-Environment Interactions b) Epigenetics
DNA is like books in a library. Limitless potential to inform and inspire…….But they need to be read.
Individual differences in neural and endocrine responses to stress brain development, Immune system Prevention Health Risks Associated with Early Adversity and Low SES Early Experience Abuse Family strife Emotional neglect Harsh discipline Health Risks Depression Drug abuse Anxiety Diabetes Heart disease Obesity
A New Science = EPIGENETICS Epigenetics the study of those environmental factors that alter whether DNA will be “expressed” without altering the DNA sequence Factors that change the likelihood that a book will be read. Champagne and Mashoodh, 2009
Epigenetic Variation nutrition stress drug use social interactions Environmental toxins hormones smoking What factors induce epigenetic changes?
When the DNA is read it is said to be “expressed” Early adversity makes some genes difficult to read. Those involved in: 1) how we cope with stress, 2) how our brain develops and works and, 3) how we fight disease. hard to read easier to read epigenetics
Social Interactions: Natural Variations in Maternal Care in the Rat: High and Low Lickers and Groomers. Differential Methylation of Glucocorticoid Receptor in rats (and humans) Michael Meaney, McGill University
Low licking and grooming High licking and grooming Cross fostering
High/HighHigh/LowLow/HighLow/Low GRir (ROD) Biological Mom / Foster Mom * * Epigenetics: Cross-fostering shows direct effects of maternal care on the expression of genes in the brain (i.e. glucocorticoid receptor) involved with coping with stress! Gl
Early Abuse in Victims of Suicide GR-1F mRNA/GAPDH (log conc.) Control Suicide Suicide - Abuse + Abuse 0.0 0.5 1.0 1.5 * GR 1-F CpG Methylation (%) Control Suicide Suicide - Abuse + Abuse 0 20 40 60 * McGowan et al 2009 Nature Neuroscience
Changes to the epigenome are a cellular memory of an environmental event New Era of Research on the Origins of our “Uniqueness”
Consequences? The mom’s behaviour (social context) affects the lifelong health of the infants via later stress reactivity The mom’s behaviour is transferred to the pups in an epigenetic manner Is this epigenetic effect is reversible, how?
Early adversity sets developmental trajectories for health and behaviour across the life-time. How: mechanisms? Gene by Environment Interaction and Epigenetics When: sensitive periods? What: early adversities? (individual differences)
Drosophila foraging gene project: Amsale Belay Ralph Greenspan Kate Osborne Joel Levine Mark Fitzpatrick Chris Reaume Locke Rowe Tony So Karla Kaun Tad Kawecki Craig Riedl Bertam Gerber Clement Kent Thomas Hendel Bryon Hughson Aaron Allen Hiwote Belay Bee foraging gene project: Yehuda Ben-Shahar Alain Robichon Gene Robinson Ant foraging gene project: Christophe Lucas Human foraging gene project James Kennedy Robert Levitan Hiwote Belay Sam Bidnur Roger Ferreira Torry Higgins Learning and Memory Fred Mery Nancy Kohn
Hypothesis: Epigenetic modification of foraging by EHMT euchromatin histone methyltransferases a family of evolutionarily conserved proteins that write part of the epigenetic code through methylation of histone 3 at lysine 9 (H3K9). EHMT is a a key epigenetic regulator of neuronal genes and processes. How does the foraging gene respond to food deprivation?
USCS genome browser “LOMB” track Loss of methylation peak in EHMT mutants foraging gene transcripts Kramer et al in prep EHMT in the transcriptional control of foraging (Mutations in EHMT affect larval foraging behaviour and adult cognition)
Kramer et al in prep FORAGING protein levels are reduced in response to food deprivation. This does not occur in EHMT mutants EHMT(-)