nuclear protein phosphatase-1: an epigenetic regulator of
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UCLEAR PROTEIN PHOSPHATASE-1: AN EPIGENETIC REGULATOR
F FEAR MEMORY AND AMYGDALA LONG-TERM POTENTIATIONFtas(bmohrpdiaralnkr2f(m2er
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. KOSHIBU,1,3 J. GRÄFF1,2 AND I. M. MANSUY*
rain Research Institute, Medical Faculty of the University Zürich andepartment of Biology of the Swiss Federal Institute of Technology,H-8057 Zürich, Switzerland
bstract—Complex brain diseases and neurological disor-ers in human generally result from the disturbance of mul-iple genes and signaling pathways. These disturbances mayerive from mutations, deletions, translocations or rear-angements of specific gene(s). However, over the pastears, it has become clear that such disturbances may alsoerive from alterations in the epigenome affecting severalenes simultaneously. Our work recently demonstrated thatpigenetic mechanisms in the adult brain are in part regu-ated by protein phosphatase 1 (PP1), a protein Ser/Thr phos-hatase that negatively regulates hippocampus-dependent
ong-term memory (LTM) and synaptic plasticity. PP1 is abun-ant in brain structures involved in emotional processing likehe amygdala, it may therefore be involved in the regulationf fear memory, a form of memory related to post-traumatictress disorder (PTSD) in human. Here, we demonstrate thatP1 is a molecular suppressor of fear memory and synapticlasticity in the amygdala that can control chromatin remod-ling in neurons. We show that the selective inhibition of theuclear pool of PP1 in amygdala neurons significantly altersosttranslational modifications (PTMs) of histones and thexpression of several memory-associated genes. These al-erations correlate with enhanced fear memory, and with anncrease in long-term potentiation (LTP) that is transcription-ependent. Our results underscore the importance of nuclearP1 in the amygdala as an epigenetic regulator of emotionalemory, and the relevance of protein phosphatases as po-
ential targets for therapeutic treatment of brain disordersike PTSD. © 2011 IBRO. Published by Elsevier Ltd. All rightseserved.
ey words: PP1, histone posttranslational modifications, fearemory, LTP, epigenetic, amygdala.
These authors contributed equally to this work.Present address: The Picower Institute for Learning and Memory,epartment of Brain and Cognitive Sciences, Massachusetts Institutef Technology, Cambridge, MA 02139, USA.Present address: UCB Pharma S.A., 1420 Braine-l’Alleud, Belgium.
Corresponding author. Tel: �41446353360.-mail address: [email protected] (I. M. Mansuy).bbreviations: CREB, cAMP response element-binding protein;REM, cAMP-responsive element modulator; dox, doxycycline;GFP, enhanced green fluorescent protein; ERK/MAPK, extracellularignal-regulated kinase/mitogen-activated protein kinase; HATs, his-one acetyl transferases; HDACs, histone deacetylases; LA, lateralucleus of the amygdala; LTM, long-term memory; LTP, long-termotentiation; NF�B, nuclear factor kappa B; NIPP1, nuclear inhibitor ofP1; PKs, protein kinases; PPs, protein phosphatases; PP1, proteinhosphatase 1; PTMs, posttranslational modifications; PTSD, post-
oraumatic stress disorder; RT-PCR, reverse transcriptase-polymerasehain reaction.
306-4522/11 $ - see front matter © 2011 IBRO. Published by Elsevier Ltd. All rightoi:10.1016/j.neuroscience.2010.11.023
30
ear memory is a form of emotional memory that recruitshe amygdala (Rodrigues et al., 2004; Maren, 2005; Sahnd Westbrook, 2008), and is often disturbed in individualsuffering from post-traumatic stress disorder (PTSD)Bremner et al., 2005; Shin et al., 2005; Ressler and May-erg, 2007). Similar to other forms of memory, the establish-ent and the maintenance of long-lasting forms of fear mem-ry largely depend on gene transcription. Recent studiesave shown that this involves epigenetic mechanisms thategulate posttranslational modifications (PTMs) of histoneroteins, in particular acetylation and phosphorylation (Kan-el, 2001; Levenson and Sweatt, 2005). Histone acetylation
s a PTM that requires histone acetyl transferases (HATs)nd deacetylases (HDACs), while histone phosphorylation isegulated by the combined action of protein kinases (PKs)nd phosphatases (PPs). In the brain, PKs such as extracel-
ular signal-regulated kinase/mitogen-activated protein ki-ase (ERK/MAPK) and mitogen- and stress-activated proteininase 1 (MSK1) are known to contribute to the epigeneticegulation of long-term memory (LTM) (Chwang et al., 2006,007). These PKs are also known to modulate long-lasting
orms of synaptic plasticity such as long-term potentiationLTP) in the lateral nucleus of the amygdala (LA), a cellularodel of fear memory (Huang et al., 2000; Schafe et al.,008). However to date, the functional role of PPs in thepigenetic regulation of fear memory and amygdala plasticityemains largely unknown.
Among the PPs expressed in the brain, serine/threo-ine protein phosphatase 1 (PP1) is one of the most im-ortant for cognitive functions. It is known to be a potentolecular suppressor of memory formation and hippocam-al LTP (Genoux et al., 2002; Munton et al., 2004; Koshibut al., 2009; Gräff et al., 2010). Here, we newly demon-trate that PP1 is also an essential modulator of fearemory, and a regulator of synaptic plasticity in the amyg-ala. We show that the nuclear pool of PP1 in neurons ofhe amygdala is involved in the control of several histoneTMs, and in the expression of specific genes, and that
nhibiting this pool by conditional transgenesis enhancesear memory and amygdala LTP.
EXPERIMENTAL PROCEDURES
nimals
ransgenic mice in C57Bl6/J background carrying a fragment ofhe nuclear inhibitor of PP1 spanning amino acids 143 to 224NIPP1*) fused to EGFP (enhanced green fluorescent protein)nd linked to a tetO promoter or co-expressed with LacZ via aidirectional tetO promoter were generated as described previ-usly (Koshibu et al., 2009; Gräff et al., 2010). Adult (3–8 months
f age) NIPP1* transgenic males were treated with doxycyclines reserved.
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K. Koshibu et al. / Neuroscience 173 (2011) 30–36 31
dox) (6 mg/g of food for at least 8 days, Westward Pharmaceu-icals). For on/off experiments, mice were treated with dox for ateast 8 days, then dox was withdrawn for at least 7 days beforeesting. Mutant off group represents NIPP1* animals not treatedith dox. Animals were maintained in accordance with the Fed-ration of Swiss Cantonal Veterinary Office and European Com-unity Council Directive (86/609/EEC) guidelines. Experimentsere run in a way to minimize the number of animals and theiruffering.
ehavior
ear conditioning was performed as previously described (Ko-hibu et al., 2005). Briefly, mice were placed in a box with ahock-grid floor for 2 min then exposed to three pairings of aontinuous 30-s tone (80 dB, 2000 Hz) and a 0.5 mA foot-shockelivered during the last 2 s of the tone. Tone-shock pairing wasepeated at 1 min interval. The freezing response (time spent witho movement except for breathing) was tested 24 h later in theame context to assess contextual fear memory, or in a newontext with a 3-min tone to assess cued fear memory.
mmunohistochemistry and Western blot
or transgene detection, paraformaldehyde-fixed brain sectionsere incubated in primary antibody against green fluorescentrotein (GFP) (1:1000, rabbit, Synaptic Systems) or �-galactosi-ase (�-gal; 1:1000, Sigma), followed by goat anti-rabbit IgGecondary antibody (1:1000, Jackson ImmunoResearch) and 3,3-iaminobenzidine (DAB) (Koshibu et al., 2009; Gräff et al., 2010).
mages were acquired with an Axiophot microscope (Zeiss) andCID Elite 7.0 software (MCID). For histone PTMs analyses,uclear fractions were prepared from the entire amygdala of naivenimals, resolved on 10–12% SDS-PAGE, transferred onto aitrocellulose membrane (Bio-Rad), then incubated in one of the
ollowing primary antibody: anti-H3 (1:2000) or -H4 (1:2000) (Up-tate); anti-phospho H3T3 (1:1000), -H3T11 (1:1000), -H3S281:1000) (Abcam) or -H3S10 (1:1000), anti acetyl-H3K9 (1:1000),H3K14 (1:1000) or -H4K5 (1:2000) (Upstate), or anti dimethyl-3K4 (1:1000) or trimethyl H3K36 (1:2000) (Abcam); H1.0 (1:000) (Abcam). Secondary antibodies were goat anti-rabbit IRDye80 nm (1:10000) and goat anti-mouse IRDye 800 nm (1:10000)Li-Cor Biosciences). The signal was normalized to histone H1.0,hen to control littermates.
uantitative real time RT-PCR (qRT-PCR)
otal RNA was extracted from the entire amygdala from behav-orally naive animals using Macherey Nagel’s NucleoSpin Kit II.DNA was synthesized using the SuperScript First-Strand Syn-hesis System for reverse transcriptase-polymerase chain reac-ion (RT-PCR) II (Invitrogen) as described previously (Koshibu etl., 2009). qRT-PCR was performed using Taqman probes (Ap-lied Biosystems) on an Applied Biosystems 7500 Thermal Cy-ler. The comparative Ct method was used to assess the differ-nce in gene expression between samples (Livak and Schmittgen,001). �-actin was used as internal control.
DAC activity assay
DAC activity was determined in nuclear extracts (50 �g) using aolorimetric assay kit (Abcam), and expressed as optical densityt 405 nm/�g protein. Activity in control samples was used forormalization.
n vitro electrophysiology
oronal slices for LA recordings were prepared from adult brain in
ehaviorally naive animals as described previously (Gräff et al., b010). Test stimulus intensity was set to evoke 30–50% of theaximum field-excitatory postsynaptic potential (f-EPSP). Re-
orded signals were amplified with an AXOPATCH 200 B amplifierAxon Instruments/Molecular Devices) and sampled usingCLAMP. aCSF contained 119 mM NaCl, 1.3 mM MgCl2.6H2O,.3 mM NaH2PO4, 2.5 mM KCl, 2.5 mM CaCl2, 26 mM NaHCO3,1 mM D-glucose. A borosilicate electrode filled with aCSF waslaced in the external capsule for stimulation, and the recordinglectrode was placed in LA. LTP was induced by three trains ofigh frequency stimulation (HFS; 100 Hz, 1 s, every 20 s) with thetimulation amplitude set at test stimulus intensity. For transcrip-ion-dependent experiments, slices were pre-incubated in 25 �Mctinomycin D at least 2 h before recording. Input-output curve andaired pulse facilitation (PPF) were conducted before the LTPxperiment. The stimulation intensity for both analyses was set athe test stimulus intensity. The inter-stimulus interval for PPF was0 ms.
tatistics
NOVAs and univariate or multivariate general linear modelGLM) were used to determine genotype and treatment effect, andukey or LSD post hoc analyses when appropriate. Statisticalignificance was set at P�0.05 (�) and P�0.01 (��). All values arexpressed as mean�SEM.
RESULTS
nhibition of nuclear PP1 alters histone PTMs andene expression in the amygdala
e investigated the effect of the inhibition of nuclear PP1n histone PTMs in the amygdala by examining the level ofistone phosphorylation, acetylation, and methylation ofeveral selected residues in the NIPP1* mice. Western blotnalyses revealed that phosphorylation of serine 10 (S10)n H3 was specifically increased by inhibition of nuclearP1. This increase was restricted to S10 as the phosphor-lation of other residues including threonine 3 (T3), T11 or28 was not altered (Fig. 1a, b). Because PP1 can form aomplex with HDACs and co-regulate histone PTMsCanettieri et al., 2003; Brush et al., 2004), we next exam-ned whether histone acetylation is also altered. We foundhat the acetylation of H3 lysine 14 (H3K14) and H4K5 wasncreased (Fig. 1a, b). Further, consistent with an increasen acetylation, HDAC activity was significantly reduced inhe NIPP1* mice (Fig. 1c), possibly as a result of theissociation of PP1 and HDACs following PP1 inhibitionKoshibu et al., 2009). H3K9 acetylation was however nothanged, most likely due to steric hindrance with theeighboring phosphorylated S10 as previously suggestedEdmondson et al., 2002; Latham and Dent, 2007).
Further, because histone methylation is often co-reg-lated with histone phosphorylation and acetylationLatham and Dent, 2007; Li et al., 2007), we also examinedhether it is affected by inhibition of nuclear PP1. We
ooked at di- and trimethylation, which can co-occur onistones and have different effects on gene transcription.imethylation of H3K4, a marker of transcriptional initia-
ion, was not altered but trimethylation of H3K36, a markerf transcriptional elongation (Li et al., 2007) was increased
y NIPP1* expression (Fig. 1a, b). These results overall
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K. Koshibu et al. / Neuroscience 173 (2011) 30–3632
ndicate that nuclear PP1 regulates specific residues oneveral histone PTMs in amygdala neurons.
Since histone PTMs are known to contribute to tran-criptional regulation, we next examined whether genexpression is altered by inhibition of nuclear PP1 in themygdala. We focused on four genes known to be impor-ant for fear memory: the transcription factors CREBcAMP response element-binding protein) and NF�B (nu-lear factor kappa B), which are involved in fear memoryormation and synaptic plasticity (Ploski et al., 2010; Lubinnd Sweatt, 2007), the CREB modulator CREM (cAMP-esponsive element modulator) (Balschun et al., 2003),nd cFos (FBJ osteosarcoma oncogene), an immediatearly gene implicated in fear conditioning and extinction inhe hippocampus (Radulovic and Tronson, 2010; Tronsont al., 2009). qRT-PCR analyses revealed that while CREBxpression was increased, NF�B expression was de-reased (Fig. 1d), but CREM and cFos expression was nothanged (Fig. 1d). Overall, these results suggest that fur-her to regulating specific histone PTMs, nuclear PP1 also
ig. 1. Histone PTMs, HDAC activity and gene transcription are alterednd (b) corresponding quantitative analyses of phosphorylation of(1,16)�5.45, P�0.05), H3T11 (Control, n�10; NIPP1*, n�9), H3S2�9), H3K14 (Control, n�9; NIPP1*, n�8; F(1,15)�7.77, P�0.05), an3K4 (Control, n�8–11; NIPP1*, n�7–10), and trimethylation of H3K36
he amygdala of NIPP1* expressing mice and control littermates. (c�0.05). (d) Quantitative RT-PCR showing CREB (Control, n�7; NIP
Control, n�10; NIPP1*, n�9; F(1,17)�7.34, P�0.05), and cFos (ormalized to control littermates. For interpretation of the referencesrticle.
ontrols the transcription of several genes in the amygdala. a
nhibition of nuclear PP1 enhances long-termontextual and tone fear memory
e next examined the effect of PP1 inhibition on fearemory. The mice were trained on contextual and tone
ear conditioning, and fear memory was tested 10 min or4 h after conditioning. Both contextual and tone fearemory were enhanced by NIPP1* expression 24 h (Fig.a, b) but not 10 min (Fig. 2c, d) after conditioning, indi-ating a selective enhancement of LTM. This enhance-ent was likely a direct effect of NIPP1* expression since
ear memory was normal and comparable to that in controlnimals in the absence of transgene expression (mutantff). Further, it could be reversed by suppression of NIPP1*xpression by dox removal in the mutant mice (Mutantn/off) (Fig. 2a, b). Finally, another transgenic line ex-ressing NIPP1* in forebrain structures but not in LA,nd showing enhanced hippocampal-dependent memoryGräff et al., 2010) had normal fear memory (Fig. 4a, b),ointing to the selective effect of PP1 inhibition in the
ition of nuclear PP1 in the amygdala. (a) Representative Western blotsontrol, n�10; NIPP1*, n�9), H3S10 (Control, n�9; NIPP1*, n�9;l, n�10; NIPP1*, n�9), acetylation of H3K9 (Control, n�9; NIPP1*,Control, n�5; NIPP1*, n�7; F(1,10)�5.53, P�0.05), dimethylation ofl, n�11; NIPP1*, n�7; F(1,16)�4.78, P�0.05) in nuclear extracts fromactivity in the amygdala (NIPP1*, n�5, Control, n�4; F(1,7)�6.87,; F(1,13)�13.7, P�0.01), CREM (Control, n�9; NIPP1*, n�8), NF�Bn�7; NIPP1*, n�6) mRNA expression in the amygdala. Data aren this figure legend, the reader is referred to the Web version of this
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TP in the amygdala is increased by inhibition ofuclear PP1 in a transcription-dependent manner
o determine whether inhibiting nuclear PP1 also impactsynaptic plasticity, we examined LTP in LA in vitro. LTPas induced in acute amygdala slices by stimulating thexternal capsule with three trains of HFS. In these condi-ions, LTP was significantly increased in the transgenicice compared to control littermates (Fig. 3a, b). The
ig. 2. Fear memory is improved by inhibition of nuclear PP1. (a)ime spent freezing 1 d after contextual fear conditioning in NIPP1*ice (n�7), NIPP1* mice off dox (n�3), NIPP1* mice on/off dox (n�6)nd control littermates (n�8) (F(3,20)�2.68, P�0.05, for effect ofreatment; Tukey post-hoc: NIPP1* vs. Control, P�0.05; NIPP1* vs.utant off, P�0.05; NIPP1* vs. Mutant on/off, P�0.05; all other com-arisons, ns) (b) Time spent freezing 1 d after cued fear conditioning
n NIPP1* (n�7), NIPP1* mice off dox (n�3), NIPP1 mice on/off doxn�6) and control littermates (n�8) before (left panel) and after (rightanel) the onset of the tone (ns for the effect of treatment before thenset of the tone, F(3,20)�3.94, P�0.05, for effect of treatment afterhe onset of the tone; Tukey post-hoc: NIPP1* vs. Control, P�0.05;IPP1* vs. Mutant off, P�0.05; NIPP1* vs. Mutant on/off, P�0.05; allther comparisons, ns). (c) Time spent freezing 10 min after contextualear conditioning in NIPP1* mice (n�5), NIPP1* mice off dox (n�3),IPP1* mice on/off dox (n�4) and control littermates (n�6), ns (d)ime spent freezing 10 min after tone fear conditioning in NIPP1* micen�5), NIPP1* mice off dox (n�3), NIPP1* mice on/off dox (n�4) andontrol littermates (n�6) before (left panel) and after (right panel) thenset of the tone, ns for both the effect of treatment before and afterhe onset of the tone. Cue-dependent memory was specific to the toneince the freezing response before tone onset was normal in theIPP1* mice. Control data are in black; NIPP1* data are in green;utant off data are in white; mutant on/off data are in green and white
tripes. Statistical significance is indicated by * P�0.05. For interpre-ation of the references to color in this figure legend, the reader iseferred to the Web version of this article.
ncreased LTP did not result from altered basal synaptic l
ransmission since input-output and paired pulse re-ponses were normal in the transgenic slices (Fig. 3d, e).urther, it was specific to NIPP1* expression in LA since itas not observed in another transgenic line expressingIPP1* in other forebrain structures except LA (Fig. 4c, d).ecause PP1 has been associated with gene transcription,e also examined whether the LTP enhancement was
ranscription-dependent. Preincubation of amygdala slicesith the transcription inhibitor actinomycin D abolished theTP increase, and restored LTP to a level comparable tohat in control slices (Fig. 3c), indicating that this increaseas transcription-dependent.
DISCUSSION
he present results identify nuclear PP1 as a regulator ofistone PTMs and a potent suppressor of fear memory andynaptic plasticity in the amygdala. They show that inhib-
ting the nuclear pool of PP1 in neurons in the amygdalalters the phosphorylation, acetylation and methylation ofpecific residues on several histone proteins, and en-ances long-term fear memory, and amygdala LTP in aranscription-dependent manner. These changes are alsohown to be associated with an alteration in the expressionf several genes. Together with previous findings (Genouxt al., 2002; Koshibu et al., 2009; Gräff et al., 2010), theresent data provides strong evidence that PP1 is a uni-ersal negative regulator of memory and synaptic plasticityhat acts in several forebrain areas to establish a specificistone code and modulate chromatin remodeling. Theyhow that H3S10 phosphorylation, H3K9 and H3K14 acet-lation, and H3K36 are regulated by nuclear PP1 acrossifferent brain areas in particular, the hippocampus and themygdala (Koshibu et al., 2009; Gräff et al., 2010). Theseistone modifications have previously been reported toe associated with transcriptional activation and canross-regulate each other (Kouzarides, 2007; Lathamnd Dent, 2007). In particular, both H3S10 phosphory-
ation and H3K36 methylation can enhance H3K14 acet-lation, while H3S10 phosphorylation can interfere with3K9 acetylation and methylation. These findings sup-ort the notion that these particular histone PTMs mayepresent a conserved epigenetic signature of LTM, andhat nuclear PP1 is a crucial regulator of these keyistone modifications.
The expression level of a subset of transcription factorsr regulators (i.e. CREB and NF�B) is altered as a conse-uence of the inhibition of nuclear PP1. However, theseenes are affected differently, and while CREB expression
s increased, NF�B expression is decreased. Notably,ther factors such as CREM or cFos are not altered. Theseesults indicate that nuclear PP1 affects several specificenes important for synaptic plasticity and memory forma-ion (Silva et al., 1998; Kida et al., 2002; Yeh et al., 2002,004; Bourtchouladze et al., 2003), but in an oppositeanner. The consequence of the changes in CREB andF�B expression is difficult to delineate precisely, but
ncreased CREB expression may provide a mechanistic
ink for the observed LTM and LTP enhancement since
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REB is important for long-lasting forms of amygdala-ependent memory (Silva et al., 1998; Josselyn et al.,001). In contrast, the decrease in NF�B may rathereaken memory since NF�B has been reported to posi-
ively regulate memory. However, NF�B activation waslso found to correlate with impaired spatial memory in aouse model of Alzheimer’s disease (Arancio et al., 2004),n effect that may be associated with the pro-inflamma-ory properties of NF�B known to lead to cell deathKaltschmidt et al., 2005). This possibility would suggesthat downregulation of NF�B may favor the reduction ofnflammatory response and facilitate LTM and synapticlasticity in the NIPP1* mice. However, until inflammatorynd/or cell death responses are assessed in the NIPP1*ice, the significance of decreased NF�B expression re-ains uncertain. Alternatively, the decrease in NF�B ex-ression may be induced to counteract the increasedREB expression, and may explain the relatively small
ig. 3. LTP in LA is enhanced in a transcription-dependent mannemmunostaining, brown signal) and placement of stimulating and recoithout actinomycin D (NIPP1*, n�9; Control, n�14) or (c) with actinom
or control versus NIPP1*, P�0.001; control versus NIPP1* with actinn NIPP1* slices, P�0.001. LA, lateral nucleus of the amygdala; Ce,epresentative traces before and after LTP are shown above the gra
ransmission in LA of NIPP1* mutant and control slices. (e) Paired pulselices. Paired pulse responses are normalized to controls. Control deferences to color in this figure legend, the reader is referred to the
nhancement in fear memory observed in NIPP1* mice. c
inally, the small memory enhancement may result fromhe fact that PP1 is inhibited only moderately, and selec-ively in neurons (neuron-specific transgene expression) inhe amygdala. Because only a few percent of neurons arectivated during fear memory (reviewed in Josselyn,010), it is possible that the NIPP1 transgene is expressed
n a subpopulation of these neurons, and thus that itseneficial effect is limited.
Overall, these data provide novel potential mechanisticnsight into the epigenetic processes involved in complexrain functions, and suggest the possibility that PP1-de-endent chromatin regulation may underlie disorders af-ecting emotional memory. While epigenetic mechanismsave been implicated in numerous neurological and psy-hiatric disorders including Alzheimer’s disease, Rett syn-rome, schizophrenia, and depression (Tsankova et al.,007; Gräff and Mansuy, 2008), their relevance for fearemory disorders such as PTSD has only recently been
ronal section of adult amygdala showing NIPP1* expression (GFPctrodes. (b, c) LTP in LA in NIPP1* mice and control littermates (b)IPP1*, n�6; Control, n�9). F(4,39)�10.83, P�0.001; Tukey post-hoc, ns; actinomycin D effect on control slices, ns; actinomycin D effectucleus of the amygdala; BLA, basolateral nucleus of the amygdala.le: 0.5 mV over 5 ms). (d) Input-output curve showing similar basalion in LA showing comparable response in NIPP1* mutant and controln black, NIPP1* mutant data are in green. For interpretation of theion of this article.
r. (a) Cording eleycin D (Nomycin Dcentral nphs (scastimulat
onsidered. There is currently no firm evidence for a direct
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nvolvement of epigenetic processes in PTSD or PTSDisk, but it was recently observed that this risk is associatedith childhood adversity and PTSD in mothers, suggestinguch involvement (Yehuda and Bierer, 2009). Given thetrong relevance of fear memory for PTSD (Bremner et al.,005; Shin et al., 2005; Ressler and Mayberg, 2007; Koe-igs and Grafman, 2009), the present data suggest theossible implication of PP1 in the etiology of PTSD. Inter-stingly, CREB, whose expression is controlled by PP1-ependent processes, has been considered as a promis-
ng target for PTSD treatment (Breithaupt and Weigmann,004). Thus, the present findings may provide a novelirection for the development of potential therapeutic ap-roaches for the treatment for brain disorders such asTSD.
cknowledgments—We thank Christine E Gee, Hansjörg Kaspernd Beatrice Vögeli for technical support, and Gregor Fischer fornimal maintenance. The lab of IMM is supported by the Univer-ity of Zürich, the Swiss Federal Institute of Technology, the Swissational Science Foundation, the National Center for Compe-
ence in Research “Neural Plasticity and Repair”.
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