Imaging Gene Effects:in Search of Neurogenetic Mechanisms

in Schizophrenia

Karen Faith Berman, M.D.Section on Integrative Neuroimaging

Clinical Brain Disorders BranchGenes, Cognition, & Psychosis Program

National Institute of Mental HealthIntramural Research Program, NIH, DHHS

karen.berman@nih.gov

Genes:

multiple susceptibility

alleles each of small effect

Cells:

subtle molecular

abnormalities

Systems:

abnormal information processing

psychiatric illness

Behavior:

complex functional interactions and

emergent phenomena

The Wisconsin Card Sorting Task

temperament

cognition

Brain dysfunction occurs at multiple levels of neuronal organization

Genes and Neuropsychiatric Illness:Why are they important?

• Majority of risk for psychiatric illness is related to inheritance

• Genes clarify effects of the environment• Genes may identify at-risk individuals• Genes transcend phenomenological

diagnosis & represent mechanisms of disease

• Genes are entry points to molecular pathways that may lead to development of new treatments

The Human Genome Sequence is Now Known (ca.2003)

Genes: 30,000

Proteins: 600,000

Variations in theGenome: > 6 million• copy number vaiations: CVNs) • single nucleotide polymorphisms: SNPs

Nucleotides: 3 billion

Single Nucleotide Polymorphisms: SNPs

single nucleotide polymorphism

AATCC → AAGCC

}

Functional SNP (truncates protein)

Complex (i.e.multifactorial) disorders like neuropsychiatric illness are polygenic and

genetically heterogeneous

affected person

unaffected

“nonpenetrant”

From: Goldman et al Nat Rev Gen 2005

Genes:

multiple susceptibility

alleles each of small effect

Cells:

subtle molecular

abnormalities

Systems:

abnormal information processing

psychiatric illness

Behavior:

complex functional interactions and

emergent phenomena

The path from here to there…

The Wisconsin Card Sorting Task

temperament

cognition

Genes:

multiple susceptibility

alleles each of small effect

Cells:

subtle molecular

abnormalities

Systems:

abnormal information processing

psychiatric illness

Behavior:

complex functional interactions and

emergent phenomena

The Wisconsin Card Sorting Task

temperament

cognition

Neuroimaging

Genes:

multiple susceptibility

alleles each of small effect

Cells:

subtle molecular

abnormalities

Systems:

abnormal information processing

psychiatric illness

Behavior:

complex functional interactions and

emergent phenomena

The Wisconsin Card Sorting Task

temperament

cognition

Clinical Phenomena Related to DLPFC Dysfunction: negative symptoms, executive function, working memory

DLPFC Physiological Dysfunction: local & system-level

Cellular Manifestations:DLPFC Pathophysio-logy & Subcortical Dopamine Dysregulation

Prefrontal Function and Striatal DA Activity Are Inversely Related

Pycock et al. 1980Luillot et al. 1987Jaskiw et al. 1988Deutch et al. 1989Kolachana et al. 1997Saunders et al. 1998Roberts et al. 1999

brainstem

striatum

prefrontal cortexGLU

GABA

DOPAMINE

DA

DA

GABA

DLPFC Pathophysiology and Striatal Dopamine Dysregulation

(Controls > Patients)

DLPFC Hypofunction in Patients

Increased Striatal F-DOPA Ki in Patients

0.008

0.009

0.010

0.011

Str

iata

l Up

take

(O

ccip

ital

Ref

eren

ce R

egio

n)

CONTROLS PATIENTS

P = 0.007, t-testP = 0.016, U test

rCBFOxygen-15 water

Presynaptic Dopamine: 6-18F-DOPA

Meyer-Lindenberg et al. Nature Neuroscience 2002

.008 .010 .012 .008 .010 .012

50

55

60

50

55

60

CONTROLS PATIENTS

No

rmal

ized

R. D

LP

FC

rC

BF

- W

CS

T

Rs = .37 p = .47

Rs = -.83p = 0.04

Striatal Ki Striatal Ki

No

rmal

ized

R. D

LP

FC

rC

BF

- W

CS

TMeyer-Lindenberg et al. Nature Neuroscience 2002

DLPFC Pathophysiology Predicts Striatal Dopamine Dysregulation

Meyer-Lindenberg et al. Nature Neuroscience 2002

Genes:

multiple susceptibility

alleles each of small effect

Cells:

subtle molecular

abnormalities

Systems:

abnormal information processing

psychiatric illness

Behavior:

complex functional interactions and

emergent phenomena

The Wisconsin Card Sorting Task

temperament

cognition

Clinical Phenomena Related to DLPFC Dysfunction: negative symptoms, executive function, working memory

DLPFC Physiological Dysfunction: local & system-level

Cellular Manifestations:DLPFC Pathophysio-logy & Subcortical Dopamine Dysregulation

Genetic MechanismsCOMT, Sub-cortical DA, & DLPFC Patho-physiology

presynaptic

postsynapticCOMT

DopamineTransporter(reuptake)

Two Mechanisms for Intrasynaptic Trafficking of Excess Dopamine

Catechol-O-methyl transferase (COMT) and dopamine trafficking in the synapse

• COMT accounts for more than 60% of DA degradation in PFC, but <15% in striatum (Karoum et al 1994)

• dopamine transporter has a minimal role in prefrontal synapses, but is abundant in striatum (Sesack et al 1998, Lewis et al 2001, Moron et al 2002, Mazei et al 2002)

• COMT has primacy for dopamine trafficking in PFC.

DLPFC Striatum

COMT mRNA expression in COMT mRNA expression in human brain: human brain: in situ hybridizationin situ hybridization

Matsumoto et al Neuroscience 2003

Allelic variability in COMT

1 27kb

COMT-S START CODON

COMT-MB START CODONTRANSMEMBRANE SEGMENT

STOP CODON

PROMOTER

5´

22q11.2222q11.23CHROMOSOME 22

…CGTG…

..AGVKD..

…CATG…

..AGMKD...

G1947 A1947

COMT-MB/S:

Val158/108 Met158/108

SOURCE: NCBI, GEN-BANK, ACCESSION # Z26491

PROMOTER

The The COMTCOMT val val158/108158/108met met PolymorphismPolymorphism

VALINE ALLELE“high-activity”thermo-stableancestral allele

METHIONINE ALLELE

“low-activity”thermo-labilehuman allele

- Of interest in schizophrenia- Poorer executive cognition & working memory- Less efficient prefrontal physiology

Adapted from Seamans et al. J Neurosci 2001

Dopamine Signaling in Prefrontal Cortex

Optimal D1-receptor activity stateSuboptimal D1-receptor activity state

Dopamine biases pyramidal neurons to respond to sustained/consistent and not to transient excitatory inputs

(i.e. DA focuses and stabilizes the response network)

“Inverted U Dose-Response” Curve

PD

Supported by findings from several studiesArnsten and Goldman-Rakic, 1986, 1990Arnsten et al., 1994Murphy et al., 1994, 1996 a,b, 1997Williams and Goldman-Rakic, 1995Verma and Moghaddam, 1996

From Goldman-Rakic 2000

PD

Predicted effects of COMT genotype on prefrontal cortical function

‘vm’ – intermediate

‘vv’ - high COMT activitylow synaptic dopamine

“mm’ – low COMT activityhigh synaptic dopamine

PD

with amphetamine

“mm’ – low COMT activityhigh synaptic dopamine

‘vv’ - high COMT activitylow synaptic dopamine

Predicted effects of COMT genotype on prefrontal cortical function

Prefrontal Function and Striatal DA Activity Are Inversely Related

Pycock et al. 1980Luillot et al. 1987Jaskiw et al. 1988Deutch et al. 1989Kolachana et al. 1997Saunders et al. 1998Roberts et al. 1999Bertolino et al. 2000, 2001Meyer-Lindenberg et al. 2002brainstem

striatum

prefrontal cortexGLU

GABA

DOPAMINE

DA

DA

GABA

COMT val

COMT Genotype Affects Midbrain Dopamine in Postmortem Brain

Val / Met Val / Val0.0

1.2

0.8

0.4

1.6

2.0

COMT GENOTYPEAkil et al., J. Neurosci, 2003

TH

mR

NA

Opt

ical

Den

sity

TH mRNA, Post-Mortem

51 yr old male, VAL/VAL

49 yr old male, VAL/MET

Categ. Box & Whisker Plot: Midbrain Ki

COMT GENOTYPE

Met / Met Val / Met

0.00250.0000

0.0030

0.0035

Mid

brai

n K

i

18F FluoroDOPA, in vivo

Val / Met Val / Val0.0

1.2

0.8

0.4

1.6

2.0

COMT GENOTYPEAkil et al., J. Neurosci, 2003

TH

mR

NA

Opt

ical

Den

sity

TH mRNA, Post-Mortem

Meyer et. al., Nature Neuroscience, 2005

COMT Genotype Affects MidbrainDopamine in vivo

Prefrontal Cortical Activity

Midbrain FDOPA and PFC rCBFby COMT Genotype

Relationship between midbrainFDOPA and PFC rCBF

by COMT genotype

Meyer Lindenberg et al. Nature Neuroscience, 2005

Adjusted data fit the “Inverted U Dose-Response” curve directly

From Goldman-Rakic 2000 Supported by findings from:Arnsten and Goldman-Rakic, 1986, 1990Arnsten et al., 1994Murphy et al., 1994, 1996 a,b, 1997Williams and Goldman-Rakic, 1995Verma and Moghaddam, 1996

Slifstein et al. Mol Psych, 2008

[11C]NNC 112 binding map Effect size for Val/Val compared with Met carriers.

COMT Genotype Also Affects D1 Dopamine Receptors

Abi-Dargham et al. J. Neurosci. 2002

The plot thickens genetically:The plot thickens genetically:multiple functional loci in multiple functional loci in COMTCOMT

5’

P2 P1

TXNRD2

5’ 3’

Exons 1 2 3 4 5 6

rs165599“Shifman et al”

val/metrs4680

- 287rs2097603

rs737865“Shifman et al”

rs 6269 rs 4633

hCV2539283* hCV11804654*

1917bp

hCV2538753*

6218bp 8821bp 4706bp

M3rs2020917

M2Rs4646310

Rel

ativ

e C

OM

T a

ctiv

ity

N=29

ANOVA p=0.0002

N=17

Rel

ativ

e C

OM

T a

ctiv

ity

N=29

ANOVA p=0.0002

N=17val/met effect on

COMTactivity

val/val met/met

Chen et al AJHG (2004)

200000

400000

600000

800000

1000000

1200000

1400000

genotype

Rel

ativ

e C

OM

T a

ctiv

ity

*

1/1 1/2 2/2

p<.05

200000

400000

600000

800000

1000000

1200000

1400000

genotype

Rel

ativ

e C

OM

T a

ctiv

ity

*

1/1 1/2 2/2

p<.05

200000

400000

600000

800000

1000000

1200000

1400000

genotype

Rel

ativ

e C

OM

T a

ctiv

ity

*

1/1 1/2 2/2

p<.05

-287 effect on COMT activity in

met/met background

Bray et al AJHG 2003

Lessons & Current Hot Topics

• Haplotype effects• Gene-gene interactions• Gene-environment interactions

Genes related to psychopathology are not about psychiatric diagnoses, per se. They are about the development and abnormal function of brain circuits related to the processing of cognitive and emotional information.

Imaging Genetics and the Future of Neuropsychiatry

Where will imaging gene effects take us?

Greater appreciation of modifiable environmental triggers?

• Primary prevention?

Outcome prediction?

New therapeutic targets?

NOVEL TREATMENTSTolcapone enhances DLPFC efficiency during

working memory in schizophreniaTHEN: COMT inhibitor previously used to augment Parkinson’s disease treamentNOW: ?Cognitive/neurophysiological enhancement for schizophrenia?

(Apud et al. Neuropsychopharmacol 2007; Apud & Weinberger NeuroRx 2006)

Genes:

multiple susceptibility

alleles each of small effect

Cells:

subtle molecular

abnormalities

Systems:

abnormal information processing

psychiatric illness

Behavior:

complex functional interactions and

emergent phenomena

The Wisconsin Card Sorting Task

temperament

cognition

Clinical Phenomena Related to DLPFC Dysfunction: negative symptoms, executive function, working memory

DLPFC Physiological Dysfunction: local & system-level

Cellular Manifestations:DLPFC Pathophysio-logy & Subcortical Dopamine Dysregulation

Genetic MechanismsCOMT, Sub-cortical DA, & DLPFC Patho-physiology

THANKS TO:NIMH INTRAMURAL RESEARCH PROGRAM

Section on Integrative Neuroimaging Zentralinstitut, MannheimPhilip Kohn Andreas Meyer-Lindenberg MD,PhDShane Kippenhan, Ph.D.

Mbemba Jabbi, Ph.D Clinical Brain Disorders BranchKatherine Roe, Ph.D. Daniel Weinberger, M.D. Tiffany Nash Bhaskar Kolachana, Ph.DJoel Bronstein Joel Kleinman, M.D., Ph.D. Deepak Sarpal Venkata Mattay, M.D. Dylan Wint, M.D. Joseph Callicott, M.D.Angela IanniJasmin Salloum, Ph.D. Joseph Masdeu, M.D. Daniel Eisenberg, M.D.

NIH PET DEPARTMENT Peter Herscovitch, M.D.

Richard Carson, Ph.D.