Genetics of psychiatry Flashcards
Risk of developing schizophrenia for the general population
1%
Risk of developing schizophrenia with an affected sibling
9%
Risk of developing schizophrenia with an affected child
6%
Risk of developing schizophrenia with an affected parent
13%
Risk of developing schizophrenia with an affected DZ twin
17%
Risk of developing schizophrenia with an affected MZ twin
48%
Most frequently developed personality disorder among patients with a relative with schizophrenia
Schizotypal disorder
Type of schizophrenia with highest MZ twin concordance
Hebephrenic
Most likely candidate genes and chromosomes for schizophrenia
COMT gene - chromosome 22
Dysbindin gene - 6p22.3
Neuregulin 1 gene - 8p21-22
DISC1 - chromosome 1
Action of COMT protein coded for by COMT gene which may be relevant to its role in schizophrenia
Degrades catecholamines including dopamine, adrenaline and noradrenaline
Inherited disorder which has a significant risk of psychosis and where the COMT gene is deleted
DiGeorge syndrome
Risk of schizophrenia among patients with DiGeorge syndrome
20-25%
Action of neuregulin seen in patients with schizophrenia which may affect presentation
Suppresses NMDA receptors leading to lowered glutamate levels
Age of onset of schizophrenia among patients with a stronger family background
Younger on average
Risk of bipolar disorder among the general population
0.5-1.5%
Risk of bipolar disorder with an affected first degree relative
5-10%
Risk of bipolar disorder with an affected MZ twin
40-70%
Genes and loci suspected in bipolar disorder
BDNF gene 11p13
DAO G72/G30 13q33
COMT 22q11
Risk of unipolar depression with an affected first degree relative
5-30%
Suggested link between BDNF gene and depression
Decreased neurogenesis in the hippocampus seen in depression, which is dependent on BDNF
Genes and chromosomes affected by mutations that are implicated in familial Alzheimer’s disease before the age of 60
Amyloid precursor protein - chromosome 21
Presenilin 1 - chromosome 14
Presenilin 2 - chromosome 1
Gene and locus with the largest impact on Alzheimer’s dementia risk
APOE - chromosome 19q
Three co-dominant alleles of APOE
2
3
4
Protective APOE allele for Alzheimer’s dementia
2
APOE allele which increases risk for Alzheimer’s dementia
4
Risk of developing Alzheimer’s dementia with an affected first degree relative
15-20%
Personality disorder with the highest heritability
Antisocial PD
Outcome of adoption studies regarding alcohol dependence
No protection in adopted children being raised away from alcohol dependent biological parents
Genes with the strongest contribution to risk of alcohol dependency
Alcohol dehydrogenase 1B and 1C - chromosome 4
Aldehyde dehydrogenase 2 - chromosome 12
First step in ethanol metabolism
Oxidation to aldehyde by alcohol dehydrogenase
Toxic intermediary in the breakdown of ethanol
Aldehyde
Second step in alcohol metabolism
Metabolism of aldehyde to acetate by aldehyde dehydrogenase
Variations in proteins leading to unpleasant effects when drinking alcohol
Active forms of alcohol dehydrogenase
Inactive forms of aldehyde dehydrogenase
Gene associated with Parkinson’s disease which codes for alpha-synuclein
SNCA
Increased risk of Alzheimer’s in people who are heterozygous for APOE4 compared to the general population
3-4 x higher
Increased risk of Alzheimer’s disease in people who are homozygous for APOE4 compared to the general population
10-30 x higher
Number of years each APOE4 allele lowers the average age of developing Alzheimer’s disease
10 years
Gene which accounts for the majority of early onset familial Alzheimer’s cases
Presenilin 1 on chromosome 14
Risk of developing schizophrenia with an affected grandparent
5%
Risk of developing schizophrenia with two affected parents
46%
Risk of developing schizophrenia with an affected half sibling
6%
Risk of developing schizophrenia with an affected first cousin
2%
Risk of developing schizophrenia with an affected nephew/niece
2%
Risk of developing schizophrenia with an affected aunt/uncle
4%
Candidate genes for schizophrenia
DTNBP1 (dysbindin) COMT NRG1 (neuregulin) G72 RGS4 DAO1 DISC1 DRD2
Heritability estimate for schizophrenia
80%
Heritability estimate for bipolar disorder
> 80%
Heritability estimate for major depression
40%
Heritability estimate for alcohol dependence
60%
Virtually inactive form of aldehyde dehydrogenase which is a common polymorphism among some Asian groups and which leads to build up of toxic acetaldehyde when drinking alcohol
ALDH2*2
Proportion of people of Taiwanese, Han Chinese, and Japanese background who have ALDH2*2
50%
Polymorphism which causes the ‘Asian flushing reaction’ when drinking alcohol
ALDH2*2
Form of alcohol dehydrogenase which causes a slow first stage metabolism of alcohol leading to less build up of toxic acetaldehyde
ADH1B*1
Proportion of Caucasians who are homozygous for ADH1B*1
95%
Forms of alcohol dehydrogenase which code for a fast first stage of alcohol metabolism leading to increased build up of toxic acetaldehyde
ADH1C*1
ADH1B*2
Proportion of Caucasians who are heterozygous for ADH1B1/ADH1B2
5%
Genes associated with familial frontotemporal dementia
C9orf72 - chromosome 9
PGRN - chromosome 17
MAPT - chromosome 17
Most common gene associated with familial frontotemporal dementia
C9orf72 - chromosome 9
Condition associated with a mutation in the shank3 gene
Autism
Risk of unipolar depression in someone with no affected relatives
5-10%
Relative increased risk of unipolar depression in someone with a first degree relative with bipolar disorder
2-3 x higher
Relative increased risk of ADHD with an affected first degree relative
55x higher
Relative increased risk of autism with an affected first degree relative
45x higher
Relative increased risk of schizophrenia with an affected first degree relative
10x higher
Relative increased risk of bipolar disorder with an affected first degree relative
7-11x higher
Relative increased risk of alcoholism with an affected first degree relative
4-6x higher
Relative increased risk of anorexia with an affected first degree relative
2-4x higher
Relative increased risk of somatisation with an affected first degree relative
3x higher
Relative increased risk of depression with an affected first degree relative
1.5-3x higher
Relative increased risk of generalised anxiety disorder with an affected first degree relative
2-5x higher
Condition associated with the susceptibility genes DRD4 and DRD5
ADHD
Condition associated with the susceptibility gene ADH2
Alcohol dependence
Condition associated with the susceptibility genes NLGN3 and NLGN4
Autism
Enzyme affected by presenilin mutations in patients with early onset Alzheimer’s
Gamma secretase
Protein mutation associated with ALS
Superoxide dismutase
Gene most strongly implicated in ADHD
Dopamine 4 receptor gene
Condition associated with SHANK3 mutation
Autism
Recent genetic focus into schizophrenia associated with intellectual disability
Copy number variants
Heritability estimate for autism
90%
Chromosome location of presenelin 2
Chromosome 1
Chromosome location of DISC1
Chromosome 1
Chromosome location of DISC2
Chromosome 1
Chromosome location of RGS4
Chromosome 1
Chromosome location of 2q
Chromosome 2
Condition associated with presenilin 2
Early onset Alzheimer’s dementia
Conditions associated with DISC1
Schizophrenia
Bipolar disorder
Condition associated with DISC2
Schizophrenia
Condition associated with RGS4
Schizophrenia - interacts with neuregulin
Condition associated with 2q
Autis
Chromosome associated with Huntington disease
Chromosome 4
Chromosome associated with Wolf-Hirschlorn disease
Chromosome 4
Chromosome associated with Cri-du-chat
Chromosome 5
Chromosome associated with dysbindin
Chromosome 6
Condition associated with dysbindin
Schizophrenia
Chromosome associated with PREP
Chromosome 6
Condition associated with PREP
Mood disorders
Chromosome associated with Williams syndrome
Chromosome 7
Conditions associated with 7q
ASD
Williams syndrome
Chromosome associated with neuregulin 1
Chromosome 8
Conditions associated with neuregulin 1
Schizophrenia
Bipolar disorder
Chromosome associated with tuberous sclerosis I
Chromosome 9
Chromosome associated with brain derived neurotrophic factor
Chromosome 11
Condition associated with brain derived neurotrophic factor
Rapid cycling bipolar disorder
Chromosome associated with trait neuroticism
Chromosome 12
Chromosome associated with Patau syndrome
Chromosome 13
Chromosome associated with ATP7B
Chromosome 13
Condition associated with ATP7B
Wilson’s disease
Chromosome associated with DAO A (also known as G72)
Chromosome 13
Conditions associated with DAO A (also known as G72)
Schizophrenia
Bipolar disorder
Chromosome associated with presenilin 1
Chromosome 14
Condition associated with presenilin 1
Early onset Alzheimer’s dementia
Chromosome associated with Prader Willi
Chromosome 15
Chromosome associated with Angelman’s syndrome
Chromosome 15
Chromosome associated with tuberous sclerosis II
Chromosome 16
Chromosome associated with C9ORF72
Chromosome 9
Condition associated with CRO9F72
Familial frontotemporal dementia
Chromosome associated with MAPT
Chromosome 17
Conditions associated with MAPT
Familial frontotemporal dementia
Progressive supranuclear palsy
Chromosome associated with progranulin (GRN)
Chromosome 17
Condition associated with progranulin (GRN)
Familial frontotemporal dementia
Chromosome associated with Smith-Magenis
Chromosome 17
Chromosome associated with neurofibromatosis 1
Chromosome 17
Chromosome associated with Edward’s syndrome
Chromosome 18
Chromosome associated with APOE
Chromosome 19
Condition associated with APOE 4
Late onset Alzheimer’s dementia
Chromosome associated with Notch3
Chromosome 19
Condition associated with Notch3
CADASIL
Chromosome associated with PrP
Chromosome 20
Condition associated with PrP
Familial CJD
Chromosome associated with Down syndrome
Chromosome 21
Chromosome associated with amyloid precursor protein
Chromosome 21
Condition associated with amyloid precursor protein
Early onset Alzheimer’s dementia
Chromosome associated with neurofibromatosis II
Chromosome 22
Chromosome associated with DiGeorge syndrome
Chromosome 22
Chromosome associated with COMT
Chromosome 22
Conditions associated with COMT
Schizophrenia
Bipolar disorder
Chromosome associated with alpha synuclein gene (SNCA)
Chromosome 4
Condition associated with alpha synuclein gene (SNCA)
Parkinson’s disease
Chromosome associated with the parkin gene (PRKN)
Chromosome 6
Condition associated with the parkin gene (PRKN)
Parkinson’s disease
Chromosome associated with the HTT gene
Chromosome 4
Condition associated with the HTT gene
Huntington’s disease
Condition associated with the HTT gene
Huntington’s disease
Chromosome associated with LRRK2
Chromosome 12
Condition associated with LRRK2
Parkinson’s disease
Chromosome associated with PINK1 gene
Chromosome 1
Condition associated with PINK1 gene
Parkinson’s disease
Chromosome associated with PARK7
Chromosome 1
Condition associated with PARK7
Parkinson’s disease
Condition associated with PARK7
Parkinson’s disease
Genes associated with dyslexia
DCDC2 DYX1C1 KIAA0319 GCFC2 MRPL19 ROBO1
Heritability of dyslexia
40-60%
Neurodevelopmental condition associated with copy number variants
Autism