Gene-Environment Interplay on Behaviour

Marla B. Sokolowski, PhD, FRSC

University ProfessorCanada 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),

Funding for our Research

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).

Rover and sitter foraging behaviour

Sokolowski 2001 Nature Review Genetics

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 1997Science

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) Fo

od In

take

5

10

15

100% 15%

*

Food Quality

RoverSitter

Enzy

me

Activ

ity

4

8

12

100% 15%

Food Quality

RoverSitter

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: sitters 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

Rover Sitter S20.5

0.55

0.6

0.65

0.7

0.75

Sham Control8-Bromo-cGMP

Prop

ortio

n m

akin

g th

e co

rrec

t cho

ice

141 120 162 154 150 154

Treatment

S2

P = 0.01

P < 0.001

Rover Sitter S2

0.45

0.5

0.55

0.6

0.65

0.7

0.75

Sham Control

KT5823

Prop

ortio

n m

akin

g th

e co

rrec

t cho

ice

111 112135 136 139 139

S2

Treatment

P = 0.01

Decreasing PKG decreases learning in roversPKG 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 differencesin neural and endocrine responses to stress brain development, Immune system

Prevention

Health Risks Associated with Early Adversity and Low SES

Early Experience

AbuseFamily strifeEmotional neglectHarsh discipline

Health Risks

DepressionDrug abuseAnxietyDiabetesHeart diseaseObesity

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

nutritionstress

drug usesocial

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/High High/Low Low/High Low/Low

0.0

0.2

0.4

0.6

0.8G

Rir (

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 m

RN

A/G

AP

DH

(lo

g

con

c.)

Control Suicide Suicide- Abuse + Abuse

0.0

0.5

1.0

1.5

*

GR

1-F

Cp

G M

eth

yla

tion

(%

)

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 GreenspanKate Osborne Joel LevineMark Fitzpatrick Chris ReaumeLocke Rowe Tony SoKarla Kaun Tad KaweckiCraig Riedl Bertam Gerber Clement KentThomas Hendel Bryon HughsonAaron Allen Hiwote Belay

Bee foraging gene project:Yehuda Ben-Shahar Alain RobichonGene Robinson

Ant foraging gene project:Christophe Lucas

Human foraging gene project James Kennedy Robert Levitan Hiwote Belay Sam BidnurRoger Ferreira

Torry Higgins

Learning and Memory

Fred Mery

Nancy Kohn

Epigenetic by Genetic Interactions

Hypothesis: Epigenetic modification of foraging by EHMTeuchromatin histone methyltransferases afamily of evolutionarily conserved proteins that write part of theepigenetic 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(-)

forR fors fors2 forR fors fors2wild type EHMT EHMT mutants

0

2

4

6

8

10

12

EHMT modulates food dependent plasticity in rover and sitter larval foraging behaviour

FedFood Deprived

Path

leng

th (c

m)

I. Anreiter, J. Kramer, M.B. Sokolowski

forR fors forR forswild type EHMT EHMT mutants

0

0.5

1

1.5

2

2.5

Adult Foraging Behaviour: Number of drops consumed in 10 min

no o

f dro

ps c

onsu

med

in 1

0 m

in

I. Anreiter, B. Hughson, J. Kramer, M.B. Sokolowski

foraging’s behavioural plasticity may be regulated via epigenetic modifications

through EHMT.

-foraging allele specific?-food deprivation specific?

-other organisms? bees, ants, flies, humans?