Our genes, Our choices Genes in context: family, founder

population, exposure

David Goldman, M.D. Laboratory of Neurogenetics,

NIAAA davidgoldman@mail.nih.gov

Disclosures: I have nothing to disclose, except this book:

The problem of neurogenetic determinism: In a causal universe is blame/praise an expedience?

Can free will/moral choice arise from Neurogenetic individuality? Ongoing, self-guided neurodevelopmental plasticity?

As genetic and neuroscience knowledge expand we steadily improve behavioral prediction, and the knowledge is increasingly applied in forensics.

Revolutions in neurogenetics since the Gothenburg, 1996 meeting

Genetics: Human genome sequence (2001) Common variation First views of function Epigenetics GWAS, Deep sequencing, Epigenetic methods

Neuroscience: Neuroimaging, including cognitive and emotional probes Deep brain stimulation, optogenetics, brainbow Circuitries of reward, emotion and cognition

Advances in forensic psychiatry since the Gothenburg, 1996 meeting

We had already learned: Much: Neurochemical, endocrine, neuropsychological, and clinical diagnostic predictors, and one or two genes.

We learned: Much: Many new predictors from genetics and neuroscience were discovered.

How psychiatric assessment changed: Not much: In 2013 we have broad (broader, even) nonetiogically defined, clinical categories

The Mallifert twins, separated at birth, randomly meet.

Heritability

The heritability of addictive disorders

h2

0

0.2

0.4

0.6

0.8

1

High

low

Mean

Goldman et al, Nature Genetics Reviews, 2005

Heritability is due to DNA variation

>22 million single nucleotide polymorphisms >3 million heterozygous nucleotides/person Hundreds of large CNV’s /person >10 Stop codons/person Humans are not a very genetically diverse species Most human variation in interindividual, not ethnic We are each neurogenetically individual

The stop codon roadmap of this talk MAOA Impulsivity rare HTR2B Impulsivity common Grm2 Alcohol preference, and more, in the rat

?’s about functional alleles

Abundance? Mode of action?

Effect size?

Functional variants that modulate human behavior act in different ways

MAOA Brunner Syndrome HTT OCD HPRT Lesch-Nyhan Syndrome ERBA ADHD NPY Obesity, Alcoholism (?) MAOA* Dyscontrol HTT* Anxiety NPY* Anxiety FKBP5* Stress response CHRNA5 Smoking COMT Cognition, anxiety BDNF Episodic memory ALDH2 Alcoholism ADH1B Alcoholism

Rare

Common Probabilistic

Deterministic

*Regulatory

Genetic effects on behavior: Context matters

Phenotype matters

Genes act in context: Functional alleles in stress-modulated behavior

HTTLPR

FKBP5

MAOA

NPY

COMT

BDNF

GCH1

Caspi et al, Science, 2003

Caspi et al, Science, 2002

Amphetamines,

Stress Met

Cognitive

Performance

Met Val

Val Amphetamines,

Stress

Frontal dopamine

….and one reason for nonlinearity of effects is inverted U-shaped curves, leading to cross-over

after Mattay et al

The COMT Val158Met locus (“warrior versus worrier”), in context of exposure

What is the phenotype?

The disease? Disease-associated measures? Temperament? Cognition? Brain circuitry? Small molecule? Protein? RNA? Epigenetic patterning?

“Clini

cal re

leva

nce”

Relationsh

ip to genotype

Serotonin Transporter Genetic Variation and the Response of the

Human Amygdala

Science 2002 July 19; 297(5580):400-3

Ahmad R. Hariri,1 Venkata S. Mattay,1 Alessandro Tessitore,1 Bhaskar Kolachana,1 Francesco Fera,1 David Goldman,2

Michael F. Egan,1 Daniel R. Weinberger1* 1 Clinical Brain Disorders Branch, NIMH, NIH. 2 Laboratory of Neurogenetics, NIAAA, NIH.

Nature Neuroscience 8, 828 - 834 (2005) 5-HTTLPR polymorphism impacts human cingulate-amygdala interactions:

a genetic susceptibility mechanism for depression Lukas Pezawas, Andreas Meyer-Lindenberg, Emily M Drabant, Beth A Verchinski, Karen E Munoz, Bhaskar S Kolachana, Michael F Egan, Venkata S Mattay, Ahmad R Hariri & Daniel R Weinberger

Statistical functional connectivity maps between bilateral amygdala and perigenual anterior cingulate cortex

LL Sx

Dilution of variance attributable to functional haplotypes of NPY,

an anxiolytic neuropeptide

mRNA expression in lymphoblastoid cell lines 0.28 Plasma NPY in healthy controls 0.17 Plasma NPY in alcohol dependent patients 0.06 fMRI response to emotional probe 0.09 Pain-induced opioid displacement (PET) 0.37 Affective response to pain 0.05 Pain threshold 0.03 Trait anxiety (Harm avoidance) 0.03

Zhou et al. Nature, 2008

Genotype

Emergent behavior

“imaging genetics”

T Value

Amygdala

Hippocampus

0

0.5

1

1.5

2

2.5

Amygdala

Hippocampus

NPY Diplotype

LH

fMR

I A

ctiv

atio

n

(n = 11) (n = 42)

P = 0.003

LL HH

(n = 18)

P = 0.003

P = 0.006

“Imaging genetics” : Emotion-induced fMRI activation is predicted by NPY diplotype

Zhou et al. Nature, 2008

CHRNA5 Asn398Asp Major “hit” from nicotine gwas Extensively replicated Role in smoking Role in lung cancer Attributable risk <0.5% of variance

CHRNA5 Asn398 predicts lower functional connectivity in smokers, smokers with other psychiatric diseases

and healthy controls

Hong et al, PNAS, 2010

Conclusions for CHRNA5 Asn398Asp in addictions

Validated, but contributes <0.5% of variance in nicotine addiction Risk allele strongly predicts connectivity including a Dorsal Anterior Cingulate/Ventral Striatal circuit involved in craving

Finding rare and uncommon variants by deep sequencing

Families

Founder populations

Model organisms

Types of Resequencing

Single genes (for example BRCA1)

Small gene panels

Chromosome regions

Large gene panels (N = 500)

Whole exome (all the genes)

Whole genome

Genotyping is actually a type of sequencing

Impulsivity: Action without foresight (but actually its much more complicated)

Key mediating trait in several psychiatric disorders including addictions (Robbins and Everitt)

Monoamine oxidase A: A gene with a “stop codon”

modifying impulsivity

In one family

Brunner et al.,

Science, 1993

Brunner syndome: X-linked dyscontrol in a Dutch family due to the MAOA C936T stop-codon

Borderline mental retardation

Dyscontrol behaviors:

Aggressive outbursts

Arson

Attempted rape

Exhibitionism

.

.

. .

.

.

C

C C C C C

C

C C

C C C C

C

C

C

T T T T

T

T

T

No fibroblast MAOA activity

Abnormal monoamine metabolism: ↓ urinary HIAA, HVA, VMA ↑ urinary normetanephrine & tyramine

T

0

5

10

15

20

25

30

35

100 200 300 400 500 600

Testosterone (pg/mL)

p=0.001

Bro

wn/

Goo

dw

in

Lif

eti

me A

ggre

ssio

n

ASPD + AUD

AUD, no ASPD no AUD, no ASPD

p=0.37

High activity MAOA-LPR

0

5

10

15

20

25

30

35

100 200 300 400 500 600

Non-additive interaction of MAOA-LPR and testosterone predicts impulsivity in men

Sjoberg et al., Neuropsychopharmacology 2007

Low activity MAOA-LPR

Conclusions for MAOA Discovery of a rare stop codon with a role in impulsivity was followed by discovery of a common functional locus. The common functional locus has strong gene by stress (Caspi et al) and gene by endocrine (Sjoberg et al) interactions in impulsivity

The serotonin HTR2B receptor: A gene with a “stop codon”

modifying impulsivity

In >100,000 Finns

Bevilacqua et al, Nature, 2010

Nelis et al. 2009

Inter- continental

Intra- continental

Estonians

Origins of samples

Africa

Asia

Finns

Finland, a population isolate for deep sequencing

NW Europe

SE Europe

Leena Peltonen: Documented that Finns have dramatically reduced heterogeneity for genetic medical diseases.

Q20* stop Blocks HTR2B

expression

HTR2B Q20* stop

Detected: Impulsive Finns violent offenders

11 12

+ HTR2B GAPDH

1.93:1 ratio of htr2b protein

Frequency: 1%, in Finns only

Associated: ASPD, alcoholism

Cosegregates with ASPD, alcoholism in families

Interactions: Male sex, possibly testosterone

*

*

*

ASPD+AUD

AUD

Sto

p Bevilacqua et al, Nature, 2010

b1 b2 b3

Gln/STOP

Q20/Q20 Q20/*20

GAPDH

HTR2B

0

-0.2

-0.4

-0.6

-0.8

0.8

0.6

0.4

0.2

HT

R2

B *

20

/Q2

0 (

log)

Q20* blocks receptor synthesis & causes variable nonsense mediated decay

1.93/1

Variable HTR2B RNA decay in 12 heterozygous Q20* lymphoblastoid

cell lines by cDNA sequencing

Blockade of receptor expression in 26 cell lines.

Consistent results with three anti-ht2b antibodies.

Characteristics of *20 carriers (174 directly observed)

The criminal offenders were cognitively normal, had

committed impulsive crimes for no financial gain, and were normal unless inebriated

3/3 double murderers were Q20/*20 heterozygotes 2/3rds of the offenders with *20 had a life-threatening

suicide attempt A *20/*20 homozygote was an alcoholic with violent

episodes CSF monoamine levels were normal *20 was not merely serving as an ancestry marker In some Finns *20 is a factor in impulsive behavior, but it

is not sufficient

Finnish datasets HTR2B *20 Allele freq

Finnish violent offenders – cases (17/228)

0.037

Controls (7/295) 0.012

Finnish Bipolar and Schizophrenia families 0.009

The Older Finnish Twin Cohort 0.013

FinnTwin12 + FinnTwin16 studies 0.012

*20 is 3x as common in cases & its frequency is 0.012, 174 directly genotyped carriers

P < 0.01

Populations ASPD/IED/BPD cases

Controls Q20*

Caucasians 247 473 1

American Indians

56 334 0

African-Americans

268 661 0

HGDP 0 1064 0

Total 571 2532 1

HTR2B Q20* was genotyped in 3104 individuals representing worldwide ethnic diversity, including the Human Genome Diversity Panel (HGDP)

*20 is found only in individuals of Finnish ancestry

Female alcoholic of Finnish ancestry

Htr2b and impulsivity: Predictive validity in htr2b -/- mice

Novelty- and D1 agonist-induced hyperlocomotion

Interaction with novel object

Delay discounting

Hyponeophagia

HTR2B Q20* extensions

Allele frequency of >0.01 confirmed in >20,000 Finns

htr2b is localized on 40% of VTA DA neurons, where it regulates DA release

htr2b modulates cocaine induced hyperlocomotion and CPP

An HTR2B haplotype, possibly functional, is associated with altered dopamine release

5-ht2b receptors are expressed on 40% of dopaminergic neurons of ventral tegmental area (VTA) (single cell RT-PCR and retrograde tracing)

Cocaine induced CPP is stronger in htr2b-/-

knockout mice

After cocaine, the decrease in burst firing was significantly larger in the Htr2b-/- KO.

VTA DA neurons exhibit single spike firing and burst firing. Burst firing leads to substantially greater DA release.

H2/H4 ratio Cases 218 0.31/0.32 Controls 176 0.25/0.40

p = 0.016

A common HTR2B haplotype predicts low expression and is associated with cocaine addiction

HTR2B diplotypes predict stress-induced dopamine release as shown by raclopride PET N = 42, with common diplotypes

HTR2B diplotypes predict HTR2B expression in lymphoblasts (62 Finns & 18 AA) with common diplotypes

Conclusions for HTR2B stop HTR2B, expressed in human brain, has a common, population-

restricted stop codon found in >100,000 Finns (out of 5.3 million)

*20 leads to variable stop codon mediated RNA decay and blocks synthesis of ht2b

*20 is associated and cosegregates with impulsive disorders

Most *20 carriers are behaviorally and cognitively normal

Additional risk elements are male sex, testosterone, alcohol

Htr2b knockout mice are more impulsive

Deep sequencing can detect rare and uncommon functional alleles linkable to common/complex as well as rare/Mendelian disorders (as in Eichler et al)

Conclusions

Alleles of different frequencies and effects influence complex behaviors such as impulsivity and addiction

Gene x environment, and gene x endocrine interactions (e.g. MAOA) occur.

Gene effects tend to be stronger on molecules and intermediate phenotypes: NPY

Rare alleles discoverable by deep sequencing contribute to emotion and complex behavior and provide clues to identify common alleles: MAOA, HTR2B Stop Codons

Families, founder populations and model organisms are powerful contexts for observing effects of rare alleles

The origins of behavioral variation include neurogenetic individuality, and choices made

DSM6: Neuroscience needed

Qiaoping Yuan

Zhifeng Zhou

Laura Bevilacqua

Colin Hodgkinson

Luc Maroteaux and lab

Markus Heilig and Lab

Roope Tikkanen Jaakko Kaprio Tiina Paunio Juho Wedenoja Jaana Suvisaari Richard Rose Leena Peltonen (Thank you, Leena) Emil Coccaro Liliana Dell’Osso

Matti Virkkunen Markku Linnoila (Thank you, Markku)

Mary-Anne Enoch

Dave Lovinger and lab

Jon-Kar Zubieta and lab

Applying genomic approaches in old animal genetic models The P/NP rat: Selected 70 generations Drink to inebriation Sustained high blood alcohol concentrations Consume alcohol for CNS effects Show withdrawal Relapse-like behavior

Exome sequence: 6 NP, 6P, 4 Wistar rats Yield: >120,000 SNPs in 50 Mb target >25,000 segregating SNPs >800 segregating missense variants 38 segregating damaging variants Including 2 segregating stop codons

Zhou et al. 2012 (submitted))

chr3

chr8 Grm2: C407*

Lcn2: Q137*

Both P and NP fixed in

opposite configuration

SNPs fixed in NP

Only NP fixed

Only P fixed

SNPs fixed in P SNPs not fixed in P

SNPs not fixed in NP

50 100 150 Mb

SNPs not fixed in WR SNPs fixed in WR

Zhou et al. 2012 (submitted))

NP

P

WR

NP

P

WR

Lcn2: lipocalin 2

Grm2: metabotropic glutamate receptor 2

Grm2 and Lcn2 are located in large genomic blocks fixed in opposite configuration in P and NP rats

0

1

2

3

4

5

6

7

8

9N

ucl

eoti

de

het

ero

zyg

osi

ty (

10

-4)

inBlock notBlock total

Random fixation in P and NP exomes 1/(1+4Ne) per generation

Nuc

leot

ide

het

ero

zygo

sity

(10

-4)

NP P Wistar Zhou et al. 2012 (submitted))

Linkage of alcohol preference to Grm2 and Lcn2 stop codons in F2’s

iP x iNP cross

Preference

iP x iNP F1 cross

Phenotype F2’s (384)

Homozygous for Stop codon

28% increase

NP P

Lo

g2

Ex

pre

ssio

n L

ev

el P = 0.0001

FDR = 0.0145

260

160

11080

60

4050

30

20

15

10

NP1NP2 P1 P2

kDa

mGluR2

GAPDH

a

b

c

d

NP

P

0

2

4

6

NP1 NP2 NP3 NP4 NP5 NP6 NP7 NP8

T G C A

0

2

4

6

P1 P2 P3 P4 P5 P6 P7 P8

Se

qR

ea

d C

ou

nt

407 C/C 407 C/* 407 */*

Alc

oh

ol C

on

su

mp

tio

n

(247) (87) (46)0

1

2

3

4

5

407 C/C 407 C/* 407 */*

Alc

oh

ol P

refe

ren

ce

(247) (87) (46)0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

e

f

c.1221C>Ap.Cys 407 *

Ligand Binding Trans-membrane

1 872

*111,837,086 111,850,133111,844,799Chr8

Grm2

mGluR2

Grm

2 *

40

7A

lle

le F

req

WistarRats

P Rats(Gen 30)

P Rats(Gen 70)

0

0.2

0.4

0.6

0.8

1

Functional effects of the Grm2 stop codon are incompletely compensated in P rats

P rats lack mGluR2 protein P rats show deficient down-regulation of neuronal firing by an mGluR2 agonist

(Dave Lovinger)

a

c.1221C>Ap.Cys 407 *

Ligand Binding Trans-membrane

1 872

*111,837,086 111,850,133111,844,799Chr8

Grm2

mGluR2

b

NP

P

Exom

eSe

qRe

ad C

ount

0

20

40

NP1 NP2 NP3 NP4 NP5 NP6

T G C A

0

20

40

P1 P2 P3 P4 P5 P6

NP P

Log2

Exp

ress

ion

Leve

l

P = 0.0001FDR = 0.0145

c

26016011080

60

4050

30

20

15

10

NP1 NP2 P1 P2

kDa

mGluR2

GAPDH

d

Baseline LY Washout

NP

P

% B

asel

ine

PS A

mpl

itud

e

LY379628 (200 nM) NP (n = 6)

P (n = 6)

e

Grm

2 *4

07A

llele

Fre

q

WistarRats

P Rats(Gen 30)

P Rats(Gen 70)

0

0.2

0.4

0.6

0.8

1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0

1

2

3

4

5

Alc

ohol

Con

sum

ptio

n

Alc

ohol

Pre

fere

nce

407 C/C 407 C/* 407 */*(247) (87) (46)

f

g

P = 0.004

P = 0.005

Alcohol Consumption Alcohol Preference

Saccharin Consumption Saccharin Preference

Quinine Consumption Quinine Preference

Pre

fere

nce

(%

) P

refe

rence

(%

) P

refe

rence

(%

)

g/k

g/d

ay

mg/k

g/d

ay

mg/k

g/d

ay

Concentration (%) Concentration (%)

Grm2+/+ Grm2-/-

Grm2+/+ Grm2-/-

Grm2+/+ Grm2-/-

Grm2+/+ Grm2-/-

Grm2+/+ Grm2-/-

Grm2+/+ Grm2-/-

Grm2 -/- mice drink more

alcohol

and the difference is not taste aversion

Vehicle

LY341495 * *

Vehicle

LY341495 * *

mGluR2 antagonist increases alcohol consumption/reward in an operant paradigm

NP P

Log2

Exp

ress

ion

Leve

l P = 0.0001FDR = 0.0145

260

160

11080

60

4050

30

20

15

10

NP1NP2 P1 P2

kDa

mGluR2

GAPDH

a

b

c

d

NP

P

0

2

4

6

NP1 NP2 NP3 NP4 NP5 NP6 NP7 NP8

T G C A

0

2

4

6

P1 P2 P3 P4 P5 P6 P7 P8

Seq

Read

Cou

nt

407 C/C 407 C/* 407 */*

Alc

ohol

Con

sum

ptio

n

(247) (87) (46)0

1

2

3

4

5

407 C/C 407 C/* 407 */*

Alc

ohol

Pre

fere

nce

(247) (87) (46)0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

e

f

c.1221C>Ap.Cys 407 *

Ligand Binding Trans-membrane

1 872

*111,837,086 111,850,133111,844,799Chr8

Grm2

mGluR2

Grm

2 *4

07A

llele

Fre

q

WistarRats

P Rats(Gen 30)

P Rats(Gen 70)

0

0.2

0.4

0.6

0.8

1

Selection of a functional Grm2 stop codon

Ancestral

Preferring (262/262)

Non-Preferring (0/130)

Selection

Actual allele counts

Subsaharan Africa

North Africa

Europe

Middle East

Central Asia

Far East Asia

Oceania

Americas

Plains Indians

Plains Indians are genetically distinct

Hodgkinson et al, PNAS 2010

Plains Indians in worldwide context

PI & SW Indians

theta

**

*

2

4

6

8

0

-log

10(p

Val

)

alpha

**

*

2

4

6

0

2

4

6

0

-log

10(p

Val

)

beta *

2

4

6

0 -l

og10

(pV

al)

Overview of Genome-wide association findings for EEG

SGIP1, ST6GalNac3, LPHN2

ST6GalNac3 UGDH

Hodgkinson et al, PNAS 2010

(BICD2) Replicated in Europeans

Replicated in Europeans

Chromosome 1 position 61472847..70759076

†

SGIP1

E

L

62M

63M

64M

65M

66M

67M

68M

69M

70M

European origin

In Plains Indians, a 20 Mb European origin chromosomal segment does predict θ EEG power

Native American origin Hodgkinson et al, PNAS 2010

Ghosh et al 2003 COGA Enoch et al 2008 – Plains Indians Porjesz et al 2002 – COGA

Chen et al 2005 – COGA

Linkage Findings for EEG Traits

*

*

*

1 2 3 4 5 6

CGGGAA .460

AGAGAA .360

CAGGAA .106

AGAGGC .026

AGAAAA .024

CGAGAA .022

The HTR2B stop codon is found on a

single haplotype background

And, in Finns of Finnish ancestry

(compared to other Europeans in HGDP)

Eig

en

ve

cto

r 2

Eigenvector 1

Finns (total = 520) Stop codon carrier

Hong L E et al. PNAS 2010;107:13509-13514

CHRNA5 Asn398 predicts lower functional connectivity of multiple circuits, including a nicotine-associated circuit

Gene x Environment can be even stronger in severely exposed populations

(HTT x Childhood stress predicts suicide attempts in African American Substance Dependent patients

(N=306)

Emotional Neglect Physical Abuse

Prob

abilit

y of

Sui

cide

Att

em

pt

Roy et al, 2007

10 20 30 40 50

CTQ Emotional Neglect

0.20

0.40

0.60

0.80

1.00

Pre

dic

ted

pro

bab

ilit

y o

f a s

uic

ide a

ttem

pt

HTTLPR genotype

high exp

low exp

0 5 10 15 20 25 30

CTQ Physical Abuse

0.20

0.40

0.60

0.80

1.00

Pre

dic

ted

pro

bab

ilit

y o

f a s

uic

ide a

ttem

pt

HTTLPR genotype

high exp

low exp

HTT genotypes Low expressing High expressing

Childhood Trauma Questionnaire

Htr2b-/- mice have increased locomotor activity after low or high doses of cocaine.

NMR-based

Structure by

S. Jähnichen

Neuropeptide Y (NPY)

Part of the lipostat system: Increases food intake and fat storage

Stress releases NPY and can lead to metabolic syndrome (Zukowska)

a 36 AA peptide

Higher levels of NPY are associated with resiliency to PTSD and

recovery, in combat veterans (Yehuda, Charney)

Prostate Brain regions

Islet cells

Adrenal Highly expressed in brain,

esp. amygdala and fetal [Novartis mRNA arrays]

Leu7Pro assoc with obesity (Koulu) and alcoholism (Lappalainen)

Pain modulatory

a. b.

H1

H4

H2

H3

H5

T

T

T

T

C

A

A

G

G

G

T

C

C

C

C

Major 6-locus

Haplotype1071 1201 5325

Promoter

Haplotype

H1&H4

H2

H3a

H5

H3b

Ins

Del

Ins

Ins

Ins

C

C

C

T

C

G

G

G

G

T

C

T

T

T

T

rs17149106

5’ 3’

rs3037354 rs16147

rs5574

rs5573

rs16139rs2390964

-883 -878 -602 -399

-1016 63

P < 0.05

NPY Promoter Haplotype

0

5

10

15

20

25

30

H1&H4 H2 H3a H3b H5

Pro

mo

ter

Ac

tiv

ity

P < 0.05

a. b.

H1

H4

H2

H3

H5

T

T

T

T

C

A

A

G

G

G

T

C

C

C

C

Major 6-locus

Haplotype1071 1201 5325

Promoter

Haplotype

H1&H4

H2

H3a

H5

H3b

Ins

Del

Ins

Ins

Ins

C

C

C

T

C

G

G

G

G

T

C

T

T

T

T

rs17149106

5’ 3’

rs3037354 rs16147

rs5574

rs5573

rs16139rs2390964

-883 -878 -602 -399

H1

H4

H2

H3

H5

T

T

T

T

C

A

A

G

G

G

T

C

C

C

C

Major 6-locus

Haplotype1071 1201 5325

Promoter

Haplotype

H1&H4

H2

H3a

H5

H3b

Ins

Del

Ins

Ins

Ins

C

C

C

T

C

G

G

G

G

T

C

T

T

T

T

rs17149106

5’ 3’

rs3037354 rs16147

rs5574

rs5573

rs16139rs2390964

-883 -878 -602 -399

-1016 63

P < 0.05

NPY Promoter Haplotype

0

5

10

15

20

25

30

H1&H4 H2 H3a H3b H5

Pro

mo

ter

Ac

tiv

ity

P < 0.05

P < 0.05

NPY Promoter Haplotype

0

5

10

15

20

25

30

H1&H4 H2 H3a H3b H5

Pro

mo

ter

Ac

tiv

ity

P < 0.05

NPY Promoter Haplotype

0

5

10

15

20

25

30

H1&H4 H2 H3a H3b H5

Pro

mo

ter

Ac

tiv

ity

P < 0.05P < 0.05

A functional promoter SNP identified by transfection

of 5 common haplotypes into a raphe neuronal line

Zhou et al. Nature, 2008

the 18th Amendment

Jan 16, 1919

The temperance movement

1789: founded by the physician

Benjamin Rush

1838: The American

Temperance Society had 1.5

million members

the 21st Amendment

Jan 16, 1933

The unhappy

The campaign

People & Cars

• Both come in many shapes, colors & sizes

• Both move about, respire and feed

• Both depend on thousands of parts

• Both may function differently or not at all due to a defect in a single part

Epistasis: Variants confer risk only in combination.

Heterogeneity: Different variants confer risk in different individuals.

Genetic Complexity

The Joker

Pleiotropy, phenocopies, incomplete penetrance, etc

Genetic complexity in affected individuals

Epistasis Heterogeneity

Genetic complexity and twin concordance

Epistasis Heterogeneity

DZ

MZ MZ

DZ

Affected Unaffected

2.19

2.23

2.38

2.69

2.71

3.72

1.52

1.73

1.96

1.84

0 0.5 1 1.5 2 2.5 3 3.5 4

MZ/DZ

Lack of evidence for epistasis in addictions

Cocaine

Sedatives Stimulants

Caffeine Hallucinogens

Opiates

Gambling

Smoking

Cannabis

Alcohol

2

Nature Genetics Reviews, 2005

Concordance Ratios

Cross-inheritance (pleiotropy) in MZ twins

Concordant

Affected Unaffected

Affected

Cross-inherited Disconcordant

General and Specific Inheritance

• General – Relatives of probands are at greater

general risk

• Specific – Relatives are at specific risk

Bottom line: Cross-inheritance studies in twins reveal both agent-specific and non-specific genetic effects (Goldman and Bergen, Arch Gen Psych, 1998)

Why are people, and some in particular, liable to addiction? Dobzhansky: nothing in biology makes sense except in the context of evolution. Seemingly, addiction makes perfect sense except in the context of evolution: in a Darwinian sense, why should human brains be differentially vulnerable to addiction?

Sistine Chapel ceiling fresco, Michelangelo, 1509

The drunkenness of Noah

Addictions are ancient, and found in all human societies

Evolutionary explanations for variation in addiction liability Addiction is not a peculiarly human characteristic: Other species display differential vulnerability to punishment-resistant reward responding. Things that bite, sting and poison us evolved psychoactive substances to which we are exposed. We even seek these out and invent more. Liability is an emergent effect of variation maintained for other reasons. Common addiction variants should have counterbalancing advantages. Predisposition emerges from genetic glitches, especially rare and uncommon alleles.

Environmentality of vulnerability: What do we know?

• Minor role of shared family environment

– But there are many family factors

– Breakthroughs in prevention could emerge from quantitatively minor factors

• Major interpopulation differences are observed for all addictions

• Major role for stress/trauma

Cir

rhos

is d

eat

hs/

100

,00

0

10

20

30

Per capita alcohol consumption liters/yr 10 15 5

US

Norway

Japan

Sweden

Italy Austria

France

Switzerland

Luxembourg

Canada

Belgium

Germany Spain

Portugal

Eire NZ

Netherlands

Australia UK

Finland

Transnational alcohol consumption & Cirrhosis

Deat

hs/

100

,00

0

10

20

19

10

Temporal variation in cirrhosis deaths [U.S.] Grant et al, 1986

19

20

19

30

19

40

19

50

19

60

19

70

19

80

Temperance

movement

Prohibition