Table 1 *Studies about epigenetic modifications involved in the etiology of common mood and anxiety disorders and suicide, January 2010-November 2011

Suicide

Poulter et al., 2008 [15]

Completed suicide

Department of Forensic Medicine, Semmelweis University Medical School, Budapest

50% in methylation analyses

100%

10 for methylation analysis

10 for methylation analysis

DNMT mRNA expression in the frontopolar cortex, hippocampus, amygdala, and dorsal vagal complex; GABAa promoter

post-mortem brain

qPCR; Methylation Mapping; Western Blot

ANOVA and t-tests with Bonferroni corrections; chi-square tests

DNMT-1 was downregulated, and DNMT-3B was upregulated among suicide completers relative to controls in the frontopolar cortex. There was no association between DNMT expression and suicide in the amygdala. In the hippocampus, DNMT-1 and 3B were downregulated in suicide completers relative to controls. DNMT-3B was elevated in the hypothalamus and the dorsal vagal complex. CG2 and 4 were hypermethylated in suicide completers relative to controls in the GABAa alpha1 subunit, and this was associated with DNMT-3b upregulation.

McGowan et al., 2008 [14]

Completed suicide following child abuse

Quebec Suicide Brain Bank matched on age, gender, and post-mortem interval; 5 cases and 1 control used for RNA expression analyses, separate 13 cases and 11 controls used for other analyses

100%

100%

18

12

rRNA promotor in the hippocampus and cerebellum

post-mortem brain

RT-PCR; methylation mapping; nearest neighbor quantification

factorial ANOVA, Bonferroni corrections; linear regression for site-specific differences

rRNA promotor was more heavily methylated in the hippocampus of suicide subjects than of controls. 21 of 26 sites had higher methylation frequency in suicide subjects relative to controls in the hippocampus. These differences were not observed in the cerebellum.

Guipponi et al., 2008 [16]

Completed suicide

Geneva, Switzerland Institute for Forensic Medicine

55% cases; 50% controls

N/I

20

20

SSAT promotor in ventral prefrontal cortex

post-mortem brain

Pyrosequencing

ANOVA and t-tests

There was no association between promotor methylation and suicide.

De Luca et al., 2009 [17]

Completed suicide

Stanley Medical Research Institute array collection; suicide and non-suicide controls matched on genotype, diagnosis, age at death, and sex

40% cases; 60% controls

N/I

10

10

5-HT2A C102 allele in the dorsolateral pre-frontal cortex

post-mortem brain

Hpall treatment followed by TaqMan Assay Q-PCR

independent t-tests

No significant difference in methylation levels of C102 were found in Brain-tissue between suicide completers and controls.

Suicide attempt

48 schizophrenics (24 suicide attempts and 24 non-attempters) pooled from Toronto Schizophrenia, and SMR populations

67% cases; 75% controls

N/I

24

24

5-HT2A C102 allele in the white blood cells

leukocytes

Hpall treatment followed by TaqMan Assay Q-PCR

independent t-tests, corrected by Bonferroni

Suicide attempters had significantly higher methylation of 102 C in peripheral leukocytes relative to controls.

Suicide attempt

57 bipolar subjects (29 suicide attempts and 28 non-attempters) pooled from Toronto Bipolar and SMR populations

34.4% cases; 35.7% controls

N/I

29

28

5-HT2A C102 allele in the white blood cells

leukocytes

Hpall treatment followed by TaqMan Assay Q-PCR

independent t-tests, corrected by Bonferroni

There was no significant difference in methylation of 102 C in the peripheral leukocytes of suicide attempters and controls.

Ernst et al., 2009 [18]

Completed suicide

Quebec Suicide Brain Bank (28 suicide completers and 11 controls); matched on age, postermortem interval, and pH. Epigenetic analyses performed on 10 subjects with low TrKB expression and 10 matched controls.

100%

100%

10 (of 28 possible)

10 (of 11 possible)

TrKB.T1 promotor region in the frontal cortex

post-mortem brain

Methylation mapping; Q-PCR and Western blot analysis; HG-U133 plus 2 microarray chip

t-test on mean methylation at two CpG dinucleotides

There was a significant difference in TrKB.T1 expression among suicide completers and non-completers. In suicide completers, downregulation was correlated with methylation frequency at sites 2 and 5 in the TrKB.T1 promotor.

McGowan et al., 2009 [19]

Completed suicide following child abuse

Quebec Suicide Brain Bank matched on age, gender, and post-mortem interval

100%

100%

24 (12 with history of child abuse; 12 without such a history)

12

NR3C1 neuron-specific glucocorticoid receptor promotor in the hippocampus

post-mortem brain

RT-PCR; methylation mapping

factorial ANOVA, Bonferroni corrections

There was decreased glucocorticoid receptor mRNA and increased cytosine methylation in abused suicide completers as compared to non-abused completers. There were no differences between non-abused completers and non- completers.

Klempan et al., 2009 [20]

Completed suicide among depressive patients

Quebec Suicide Brain Bank matched on age

100%

100%

16 (4 included in methylation analysis)

13 (4 included in methylation analysis)

QKI promotor in the orbitofrontal cortex

post-mortem brain

HG-U133 A/B microarray; methylation mapping; TaqMan gene expression assays

t-test

Suicide completers had significantly lower mRNA levels of QKI in 11 cortical regions and in the amygdala. However, there were no significant differences in methylation levels at the QKI promotor by suicide status.

Keller et al., 2010 [22]

Completed suicide

Biological Bank of the Institut za Varovanje Zdravja, Ljubljana (Slovenia)

48% cases; 48% controls

100%

44

33

Overall methylation in Wernicke's area; BDNF promotor region methylation in Wernicke's area

post-mortem brain

Pyrosequencing; MassARRAY; bisulfite genomic sequencing

ANOVA and ANCOVA adjusted for sex and age

BDNF promotor IV methylation was significantly higher in suicide completers relative to controls. Higher BDNF methylation was associated with lower BDNF transcript IV. There was no difference in genome-wide methylation levels between suicide completers and controls. In suicide completers with high methylation levels, there were lower BDNF mRNA levels.

Fiori et al., 2010 [25]

Completed suicide

Quebec Suicide Brain Bank as well as a Quebecois sample of healthy controls

100%

100%

10 (of 40 possible)

10 (of 56 possible)

SMS and SMOX promotor region in the BA 8/9, as well as histone methylation of H3K27me3

post-mortem brain

Methylation mapping and chromatin immunoprecipitation

t-test with correction for mutliple testing

There were no associations between methylation at any locus and suicide. Histone H3k27me3 methylation was not associated with suicide.

Fiori et al., 2011a [24]

Completed suicide

Quebec Suicide Brain Bank as well as a Quebecois sample of healthy controls

100%

100%

10

10

SAT1 promotor in the prefrontal cortex; histone methylation of H3K27me3

post-mortem brain

Methylation mapping and chromatin immunoprecipitation

t-test

CpG methylation at the SAT1 promotor was not associated with suicide, although it did predict decreased SAT1 expression. Histone H3k27me3 methylation was not associated with suicide completion.

Fiori et al., 2011b [23]

Completed suicide

Quebec Suicide Brain Bank as well as a Quebecois sample of healthy controls; suicide completers selected on over-expression of AMD1, ARG2, OAZ1, and OAZ2

100%

100%

34

34

Histone H3Kme3 in the inferior frontal gyrus

post-mortem brain

Chromatin immunoprecipitation

t-test and pearson correlation

Suicide completers had significantly higher H3Kme3 levels at OAZ1. H3Kme3 was positively correlated with expression of ARG2 and OAZ1.

Keller et al., 2011 [21]

Completed suicide

Biological Bank of the Institut za Varovanje Zdravja, Ljubljana (Slovenia)

61% cases; 52% controls

N/I

18

18

BDNF receptor (TrkB) in Wernicke's area; BDNF promotor in Wernicke's area

post-mortem brain

MassArray

t-tests

There were no significant differences in TrkB promotor methylation between suicide completers and controls. BDNF promotor IV methylation was significantly higher in suicide completers relative to controls.

Mood Disorders

Philibert et al., 2008 [26]

Major depression

Iowa Adoption Study participants

50%

93%

68 (history of MD); 17 (current MD)

124 (no history of MD); 175 (no current MD)

5HTT promotor SLC6A4

lymphoblast

RT-PCR; MassArray quantitative methylation

ANOVA and linear regression with Bonferroni corrections

There was no relationship between methylation and mRNA expression overall. There was no relationship between SLC6A4 expression and life history of MD or current MD.

Alt et al., 2009 [27]

Major Depressive Disorder

Dutch Brain Bank; Matched on age, sex, brain weight, post-mortem delay and pH of CSF

67% cases; 50% controls

N/I

6

6

Glucocorticoid receptor promotor region (1 J, 1E, 1B, 1 F) of amygdala, hippocampus, inferior postulate gyrus, cingulate gyrus, nucleus accumbens

post-mortem brain

QIAamp DNA Mni kit (Qiagen); pyrosequencing

Mann–Whitney U-test, corrected by Bonferroni

GR transcript levels were homogenous by disease status. Exon 1 F expression was reduced among MDD patients relative to controls. There were no significant differences in methylation patterns between groups between different brain regions.

Olsson et al., 2010 [28]

Depression

Nested cohort from the Victorian Adolescent Health Cohort Study, a population-representative sample of 2032 young Australians in Victoria

55%

96%

25

125

5HTT promotor

buccal cells

MassArrray

logistic regression, Bonferroni corrections

Buccal cell 5HTT methylation and depression were not associated either over the entire promotor or in subregions identified by PCA. However, there was a joint effect of 5HTT methylation and the s-allele variant on risk for depression.

Fuchikami et al., 2011 [29]

Major depression

Japanese sample of DSM-IV criteria depressed patients and health controls from four academic medical centers

N/I

N/I

20

18

BDNF promotor

white blood cells

MassArray

2-dimensional hierarchical clustering and t-tests

Mean methylation rates of CpG 1 but not 4 at the BDNF promotor was associated with depression.

Uddin et al., 2011 [12]

Lifetime Depression

Detroit Neighborhood Health Survey, a multiethnic representative survey of low- income neighborhoods in Detroit, MI

40%

14%

33

67

non-specific

whole blood

HumanMethylation 27 beadchip; pyrosequencing of two loci

McNemar's chi-squared tests for overall methylation; Functional annotation clustering analyzed via Wilcoxon test, alpha < 0.01

Cases had fewer uniquely unmethylated and methylated genes than controls. Methylated genes were associated with lower gene expression. FACs associated with multicellular organismal development, lipoprotein activity, and hydrolase activity were uniquely unmethylated, while those associated with protease activity, metabolic processes, and cell development were uniquely methylated in cases. In controls, FACs associated with brain development, tryptophan metabolism, and neuormuscular processes were uniquely unmethylated, while those involved in signaling, lipocalin, and tissue development were uniquely methylated.

Anxiety Disorders

Elser et al., 2006 [13]

Panic disorder

N/I

N/I

N/I

24

N/I

NET promotor and exon 9

white blood cells

CpGenome DNA modification it and ABI Prism 7700 Sequence Detection System; chromatin immunoprecipitation

t-test on mean methylation in promotor region

There was a significant difference in NET promotor methylation among patients with panic disorder relative to healthy controls. Promotor regions were also enriched with the MeCP2 co-repressor complex.

Uddin et al., 2010 [30]

Post-traumatic stress disorder

Detroit Neighborhood Health Survey, a multiethnic representative survey of low-income neighborhoods in Detroit, MI

40%

14%

27

77

non-specific

whole blood

HumanMethylation 27 beadchip

McNemar's chi-squared tests for overall methylation; Functional annotation clustering analyzed via Wilcoxon test, alpha < 0.01

There was no difference in overall methylation level among PTSD cases relative to controls, however the number of uniquely methylated genes did differ by disease status. Uniquely unmethylated genes in PTSD cases were associated immune system involvement, including TLR1, TLR3 (innate immune system), IL8, LTA, and KLRG-1 (adaptive immune system).

Uddin et al., 2011 [31]

Post-traumatic stress disorder

Detroit Neighborhood Health Survey, a multiethnic representative survey of low-income neighborhoods in Detroit, MI

40%

14%

27

77

33 genes previously described in the literature as associated with PTSD

whole blood

HumanMethylation 27 beadchip

Logistic regression to assess the relation between site-specific methylation and lifetime traumatic events adjusted for race, smoking, gender, age, socioeconomic status, peripheral cell count, and medication

Only MAN2C1 methylation interacted with number of potentially traumatic events to significantly predict lifetime PTSD. Increases in both factors were associated with increased lifetime PTSD risk.

Smith et al., 2011 [32]

Lifetime post- traumatic stress disorder

Cohort of African-American pariticipants recruited at clinical waiting rooms in a low-income, urban context

63% of cases; 60% of controls

0%

51 (25 with childhood trauma)

53 (21 with childhood trauma)

non-specific

whole blood

HumanMethylation 27 beadchip

linear mixed model adjusted for age, sex, and chip effects, with adjustment for multiple testing using the false discovery rate method

Lifetime PTSD was associated with increased methylation overall. Lifetime PTSD was associated with increased methylation in TPR, ANXA2, CLEC9A, ACPT5, and TLR8 compared to controls. CPG site methylation at BDNF and CXCL1 were associated with lifetime PTSD. There was no association between methylation at NR3C1 and SLC6A4 and PTSD.