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Genes and behavioral
disorders
A-Min Huang, Ph.D.
Associate Professor, Department of
Physiology, NCKU, College of Medicine
2010
Objective
• To learn the development of psychiatric
genetic approaches
–
–
–
–
The gene-to-disorder approach
The endophenotype approach
The gene-environment interaction approach
Integrating experimental neuroscience and
the gene-environment interaction approach
Main reference:
Nat. Rev. Neurosci. 7:583-590, 2006
Approaches to psychiatric
genetics research
Nat. Rev Neurosci 7:583-590, 2006
The gene-to-disorder approach
The gene-to-disorder approach
• Assumption
– Direct linear relations between genes and
behavior
• Goal
– To correlate psychiatric disorders with
individual differences in DNA sequence
• Methodology
– Linkage analysis
– Association analysis
– Microarray
Summary
Susceptibility loci for
schizophrenia and bipolar disorder
Susceptibility loci for schizophrenia:
Chromosome 1, 4, 5, 6, 8, 9, 10,
13, 15, 17, 22, X
Susceptibility loci for bipolar:
Chromosome 1, 3, 4, 12, 13, 18, 21,
22, X
13q32; 22q11-13
Finding Schizophrenia genes
DTNBP1: dystrobrevin-binding protein 1, ch6
NRG1: Neuregulin 1, ch8
DAO: D-amino acid oxidase, ch12
DAOA: D-amino acid oxidase activator, ch13
RGS4: Regulator of G protein signaling 4, ch1
CAPON: C terminal PDZ domain ligand of neuronal nitric oxide synthase, ch1
PPP3CC: protein phosphatase 3, catalytic subunit, ch8
COMT, DRD2, DRD3, HTR2A
The Journal of Clinical Investigation 115:1440-1448, 2005
RGS4 gene and schizophrenia -found by microarray studies
Strategy
High-density cDNA microarray analysis
PFC area 9 from 6 patients and 6 controls
Verification by in situ hybridization
Comparison in a second cohort of
schizophrenic and control
subjects (5 pairs)
Mirnics K, et al. (2000) Neuron 28, 53–67
Prefrontal cortex as a major
locus of dysfunction
• Reduction in
gray matter
volume
• Increase in cell
packing density
• Reduced neuropil
hypothesis
Dual color labeling
Control experiment I
Cortical mRNA from a control subject
Cy3 labeling
Cy5 labeling
Incyte UniGEM-V microarray
7000 cDNA spots (250 gene groups)
Signal ratio of each cDNA (Cy5/Cy3)
Six matched pairs compared
Cortical
mRNA
from C1
Cy3
labeling
Cortical
mRNA
from S1
Cy5
labeling
Cortical
mRNA
from C2
Cy3
labeling
Cortical
mRNA
from S2
Cy5
labeling
…
…
…
Cortical
mRNA
from C6
Cy3
labeling
Cortical
mRNA
from S6
Cy5
labeling
Cy5/Cy3 intensity across six pairwise
comparisons
Cy3
250 gene groups were analyzed. More than 98% of the gene
groups were not different.
3735 genes are detectable; 4.8 % of the genes having  |1.9|
fold; 2.6% were up-regulated; 2.2 % were down-regulated.
RGS expression in PFC - microarray
RGS : Regulator of G
protein signaling,
GTPase activating
protein that will
reduce response
duration of
postsynaptic neuron
5HT2 & D2R are Gprotein coupled
receptor
Molecular Psychiatry (2001) 6, 293–301
Confirmation by in situ hybridization
RGS4 mRNA was decreased in the cortex of the schizophrenia patients
Molecular Psychiatry (2001) 6, 293–301
Schizophrenia
Major depression
Molecular Psychiatry (2001) 6, 293–301
Genomic organization of RGS4
and flanking regions
Established single nucleotide polymorphism, SNP
Human Molecular Genetics (2002) 11: 1373–1380
Support for RGS4 as a Susceptibility
Gene for Schizophrenia
(G/A)
(T/G)
(G/A)
(A/G)
Control: 675; Case: 683
Control: 673; Case: 773
BIOL PSYCHIATRY (2004) 55:192–195
SNP1: A/G
SNP4: T/G
SNP1: A/G
SNP18: A/G
BIOL PSYCHIATRY (2004) 55:192–195
Confirming RGS4 as a Susceptibility Gene
for Schizophrenia
Not schizoaffective
249 cases and 231 controls from Ireland
American Journal of Medical Genetics (2004) 125B:50–53
American Journal of Medical Genetics (2004) 125B:50–53
Genetics of mood disorder
Biol Psychiatry 60:84-92, 2006
(continued)
Biol Psychiatry 60:84-92, 2006
Problems with the gene-todisorder approach
• Replication failures are routine
• Overall progress has been slow
The endophenotype approach
Endophenotypes (I)
• Specificity:
– The endophenotype is more strongly
associated with the disease of interest than
with other psychiatric conditions.
• State-independence:
– The endophenotype is stable over time and
not an epiphenomenon of the illness or its
treatment.
• Heritability:
– Variance in the endophenotype is associated
with genetic variance.
Neuropsychopharmacology (2004) 29, 1765–1781
Endophenotypes (II)
• Familial association:
– The endophenotype is more prevalent among
the relatives of ill probands compared with an
appropriate control group.
• Cosegregation:
– The endophenotype is more prevalent among
the ill relatives of ill probands compared with
the well relatives of the ill probands.
• Biological and clinical plausibility:
– The endophenotype bears some conceptual
relationship to the disease.
Rationale for the endophenotype
approach
Endophenotypes
Endophenotypes
The above two approaches
are main-effect approaches
Assumption:
genes cause disorder
The gene-environment
interaction approach
The gene-environment interaction
approach
• Assumption
• Environmental pathogens cause
disorder
• Genes influence susceptibility to
pathogens
• Two observations
• Mental disorders have
environmental causes
• People show heterogeneity in their
response to those causes
Environmental risk factors for
major depression
• Childhood
– genetic risk, disturbed family environment, childhood sexual abuse,
and childhood parental loss
• Early adolescence
– neuroticism, self-esteem, and early-onset anxiety and conduct
disorder
• Late adolescence
– educational attainment, lifetime traumas, social support, and
substance misuse
• Adulthood
– History of divorce and past history of major depression
• The last year
– Marital problems, difficulties, and stressful life events
Am J Psychiatry 159:1133-1145 (2002)
Role of MAOA genotype in the cycle
of violence in maltreated children
Science 297, 851-854, 2002
VNTR polymorphism of MAOA
(30 bases)
Hum Genet 103:273–279, 1998
行為異常
性情傾向暴力
暴力犯罪
反社會人格異常症狀
Science 297, 851-854, 2002
Influence of Life Stress on
Depression: Moderation by a
Polymorphism in the 5-HTT Gene
Science 301, 386-389, 2003
Map of the human 5-HTT
promoter
Serotonin transporter gene
polymorphism: s and l forms
17q1 1.2
J. Neurochem. 66 : 2621-2624, 1996
l allele and 5-HTT expression
• Homozygous for the l allele have higher
concentrations of 5-HTT mRNA and
express nearly twofold greater 5-HT
reuptake in cultured human lymphoblast
cell lines
Promoter activity
5-HT uptake, binding, and
mRNA concentration
Distribution for neuroticism
scores and percentage
Science 301, 386-389, 2003
Science 301, 386-389, 2003
Cannabis use x psychosis x COMT
genotype polymorphism
Biol Psychiatry 57,1117-1127 (2005)
Biol Psychiatry 57,1117-1127 (2005)
Biol Psychiatry 57,1117-1127 (2005)
How does genotype moderate the
psychological effects of cannabis use?
Nat. Rev. Neurosci. 7:583-590, 2006
Are gene-environment interaction
studies replicated?
• Most gene-environment interaction
findings have emerged too recently to
be evaluated
• Two of these findings are promising
– MAOA genotypes and maltreatment
– 5-HTT long and short genotypes and life
stress
5-HTT long and short genotypes
and life stress-replicated studies
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•
•
•
•
•
•
•
Mol. Psychiatry 9, 908-915 (2004)
Mol. Psychiatry 10, 220-224 (2004)
Arch. Gen . Psychiatry (in the press)
PNAS 101, 17316-17321 (2004)
Bio. Psychiatry 59, 673-680 (2006)
Arch. Gen . Psychiatry 62, 529-535 (2005)
Br. J. Psychiatry 188, 210-215 (2006)
Am. J. Psychiatry (in the press)
Int. J. Neuropsychopharmacol 7 Jun 2006
PNAS 101:17317-17321,
2004
Biol Psychiatry 59:673-680, 2006
Biol Psychiatry 59:673-680, 2006
5-HTT long and short genotypes and
life stress- failures to replicate
• Psychol. Med. 35, 101-111 (2005)
• Bio. Psychiatry 59, 224-229 (2006)
• Females or males?
• Younger or older adults?
• First onset or recurrent depression?
Limitation of the G-E approach
• Not able to understand the biological
mechanisms involved in an interaction
Integration of experimental
neuroscience with the geneenvironment interaction approach
Phase a
Phase b
Phase c
Nat. Rev. Neurosci. 7:583-590, 2006
Neuroscience
evidence base
Epidemiological
G-E interaction
research
Experimental
neuroscience
MAOA
knock-out
mice
MAOA gene
polymorphism
and the cycle of
violence
Imaging study of
the MAOA gene
polymorphism and
emotional arousal
BOLD
fMRI
Science. (2002) 297:400-403
Science. (2002) 297:400-403
DRD4 VNTR polymorphism and
substance-use disorders

Candidate genes
ˇ
Addiction
Subjects’
reactions
Craving
Experimental
stimuli
Alcohol
or
Cigarette
Genotype
DRD4 VNTR
DRD4 VNTR polymorphism
Associations of the seven-repeat (7R) allele of the human dopamine receptor
D4 (DRD4) gene with both the personality trait of novelty seeking and attention
deficit/hyperactivity disorder have been reported.
The 7R variant exhibits a blunted ability to reduce cAMP levels, in
comparison with that of the common 4R variant (Asghari et al. 1995).
Am. J. Hum. Genet. 74:931–944, 2004
Nat. Rev. Neurosci. 7:583-590, 2006
Towards a nomological
network
A nomological network refers to the
interlocking system of laws — the predicted
pattern of theoretical relationships — which
define a construct.
•
1. Animal models of environmental
pathogen exposure are needed
•
2. Studies that compare human
genotype groups on their responses to
experimentally administered
environmental stimuli are needed
• 3. more epidemiological cohort studies
should collect neuroscience
measurements
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–
–
–
–
DNA
Neuropsychological tests
Heart rate reactivity
Immune system markers
Imaging paradigms
• 4. move beyond SNP to a set of gene
polymorphisms
• 5. Genome-wide scans for new disease
genes
• 6. to explain demographic patterns of
disorder
– Males or females
– Younger or older
Conclusion:
Neuroscience and gene-environment
interaction research are joining
forces to look for answers
• Why do some people who are exposed to an
environmental pathogen develop mental disorders,
while others do not?
• Why do some disorders excessively afflict one sex or
one age group?
• How can tow people experiencing the same
environmental pathogen later develop very different
disorders?
• How does an environmental pathogen, especially one
that is psycho-social in its nature, get under the skin
to alter the nervous system and generate mental
disorders?
Mid-term paper
• Please design a study that compare
human genotype groups on their
responses to experimentally
administered environmental stimuli
• By October 29, 2010.