Citation: Transl Psychiatry (2011) 1, e35, doi:10.1038/tp.2011.38& 2011 Macmillan Publishers Limited All rights reserved 2158-3188/11

www.nature.com/tp

Impact of early adverse experience on complexity ofadult-generated neurons
AT Leslie1,4, KG Akers1,4, AD Krakowski1,2, SSD Stone1,2, M Sakaguchi1, M Arruda-Carvalho1,2 and PW Frankland1,2,3

New neurons continue to be generated in the dentate gyrus (DG) region of the hippocampus throughout adulthood, and abnormal
regulation of this process has emerged as an endophenotype common to several psychiatric disorders. Previous researchshows that genetic risk factors associated with schizophrenia alter the maturation of adult-generated neurons. Here, weinvestigate whether early adversity, a potential environmental risk factor, similarly influences adult neurogenesis. During thefirst 2 weeks of postnatal life, mice were subject to repeated and unpredictable periods of separation from their mothers. Whenthe mice reached adulthood, pharmacological and retroviral labelling techniques were used to assess the generation andmaturation of new neurons. We found that adult mice that were repeatedly separated from their mothers early in life had similar
rates of proliferation in the DG, but had fewer numbers of cells that survived and differentiated into neurons. Furthermore,neurons generated in adulthood had less complex dendritic arborization and fewer dendritic spines. These findings indicate thatearly adverse experience has a long-lasting impact on both the number and the complexity of adult-generated neurons in the
hippocampus, suggesting that the abnormal regulation of adult neurogenesis associated with psychiatric disorders could arise
from environmental influence alone, or from complex interactions of environmental factors with genetic predisposition.
Translational Psychiatry (2011) 1, e35; doi:10.1038/tp.2011.38; published online 30 August 2011
Introduction
Accumulating evidence suggests a link between abnormal
adult hippocampal neurogenesis and psychiatric disorders,
including schizophrenia, depression and drug addiction,
leading to the idea that aberrant integration of new neurons
in the adult brain may contribute to mental illness.1,2Consistent with this idea, mutations of genes associatedwith an increased risk of schizophrenia (for example,
DISC1, RELN and NPAS3) alter the morphological maturation and migration of adult-generated neurons in thedentate gyrus (DG).3–5 However, although genes exert astrong influence on the likelihood of developing psychiatricdisorders, early environmental factors, such as social exclusion from peers and caregiver abuse or neglect, also havea significant role.6,7Here, we investigate whether adverse experiences earlyin life can lead to changes in the regulation of hippocampal neurogenesis during adulthood. Early adversity wasmodelled in mice using a chronic unpredictable maternal
separation paradigm,8,9 in which mouse pups were separated from their mothers for 3 h a day during the first
2 postnatal weeks. When these mice reached adulthood,
we assessed the proliferation, survival, differentiation andmorphological maturation of new neurons in the DG. We
found that, similar to some genetic manipulations, adverse
early experiences have a long-lasting impact on both thenumber and the complexity of hippocampal neurons generated during adulthood.

Materials and methods
Mice. Mice were obtained from a cross between aprimiparous 129Svev female mouse and a C57Bl/6 male
mouse (Taconic). Breeding occurred in our colony at the
Hospital for Sick Children. The day of birth was designatedas postnatal day (P) 0, and weaning occurred on P21. After
weaning, mice were housed in groups of 2–5, andmaintained on a 12-h light/dark cycle (lights on at
0700 hours) with free access to food and water. All
experimental procedures were approved by the Animal
Care Committee at the Hospital for Sick Children.
Unpredictable maternal separation. Mouse pups were
subjected to unpredictable maternal separation for 3 h a
day from P1 to P14 (n ¼ 9 litters). On each day, dams were
removed from their home cages and individually placed inseparate cages located in a different room. The home cages
containing the pups were placed on heating pads to maintainthe nest temperature at 30–31 1C. The separation occurred
randomly at one of the three possible times during the day(0900–1200, 1200–1500 or 1500–1800 hours). Control pups
were left undisturbed in their home cages with their dam,
except for weekly cage changes (n ¼ 10 litters). There were
no differences between separated and control group in litter
size (separated: 7.6±0.5 pups; control: 7.8±0.6 pups; groupeffect: P40.05) or sex ratio within litters (separated: 4.4±0.6
males, 3.1±0.4 females; control: 3.6±0.5 males, 4.2±0.4

1
Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada; 2Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
and 3Department of Physiology, University of Toronto, Toronto, Ontario, Canada
Correspondence: Dr PW Frankland, Neurosciences and Mental Health, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, M5G 1X8 Canada.
E-mail: paul.frankland@sickkids.ca
4These authors contributed equally to this work.
Keywords: adult neurogenesis; dentate gyrus; depression; hippocampus; maternal separation; schizophrenia

Received 29 July 2011; accepted 3 August 2011

Early adversity and adult neurogenesis
AT Leslie et al2females; group  sex interaction: P40.05). To reduce thepossibility of litter effects on dependent measures,10 the
separated and control mice used for each experiment were
sampled from several different litters (proliferation n ¼ 15
litters; survival n ¼ 14 litters; morphology n ¼ 8 litters).
5-Bromo-20 -deoxyuridine (BrdU) injection. Cells undergoing division were labelled with BrdU, a thymidine analog
that incorporates into the DNA of cells during the S-phase of
the cell cycle. BrdU was dissolved in 0.1 M phosphatebuffered saline (PBS) at a concentration of 10 mg ml1. At
P60, mice received two injections of BrdU per day(100 mg kg1; 5 h apart) for 3 consecutive days. To assess
cell proliferation, mice were perfused 24 h after the last BrdU
injection (separated: n ¼ 15, 7 male, 8 female; control:
n ¼ 15, 6 male, 9 female). To assess cell survival anddifferentiation, mice were perfused 4 weeks after the last
BrdU injection (separated: n ¼ 16, 9 male, 7 female; control:
n ¼ 18, 9 male, 9 female). After deep anesthesia with chloral
hydrate, mice were perfused transcardially with PBS followed
by 4% paraformaldehyde. Brains were removed and placed
in 4% paraformaldehyde for 48 h at 4 1C and then transferred
to PBS. Serial coronal sections (40 mm) were obtained acrossthe entire anterior–posterior extent of the hippocampus using
a vibratome. Sections were stored in PBS with 0.01% sodium
azide at 4 1C.
Green fluorescent protein (GFP) retrovirus infusion.
New neurons were labelled by CAG promoter-driven GFP
expression, following infection with a replication-deficient
retroviral vector based on the Moloney murine leukemia
virus.11 The retrovirus was prepared in our laboratory bytransfecting Plat-gp cells with plasmids containing an
amphotropic envelope (vsvg) and the transgene (pCAGGFP). Ultra-high-speed centrifugation was used toconcentrate the virus into a high-titer solution (5  108–9
infection units ml1). At P60, mice (separated: n ¼ 5, 3 male,
2 female; control: n ¼ 5, 2 male, 3 female) were treated withatropine (0.1 mg kg1) and anesthetized with chloral hydrate(400 mg kg1). Using stereotaxic procedures, 1.0 ml of theretrovirus was infused into the DG bilaterally (2.2 mm AP,±1.6 mm ML and 2.0 mm DV relative to bregma). The
retrovirus was delivered using a glass micropipette, and apump maintained the infusion rate at 0.15 ml min1. The
pipette was left in place for 5 min after each infusion. Mice were
postoperatively treated with ketoprofen (5 mg kg1). Mice were
perfused 4 weeks after retrovirus infusion. Serial coronal
sections (50 mm) were obtained across the entire anterior–posterior extent of the hippocampus using a vibratome.
Immunohistochemistry. For BrdU labelling, free-floating
sections were treated with 1 N HCl at 45 1C for 30 min, 1%
H2O2 at room temperature (RT) for 15 min and 0.2 M glycine
in PBS at RT for 10 min. Sections were incubated with theprimary antibody (rat anti-BrdU, 1:1000, monoclonal
antibody, Accurate Chemicals, Westbury, NY, USA) at RT
overnight and the secondary antibody (Alexa-488 goat antirat, 1:1000, Molecular Probes, Carlsbad, CA, USA) at RT for
2 h. For the 4-week survival group, sections were alsolabelled with neuronal-specific nuclear protein (NeuN) using
Translational Psychiatry

an additional primary antibody (mouse anti-NeuN, 1:1000,
Chemicon, Billerica, MA, USA) and a secondary antibody(Alexa-568 goat anti-mouse, 1:1000, Molecular Probes).
Antibodies were diluted in blocking solution (2.5% bovine
serum albumin, 5% normal goat serum and 0.3% Triton
X-100 in PBS). Sections were counterstained with
40 ,6-diamidino-2-phenylindole (1:10 000) and mounted onslides with Permafluor anti-fade medium (ThermoScientific,
Waltham, MA, USA).
For GFP labelling, free-floating sections were incubatedwith the primary antibody (rabbit anti-GFP, 1:500, Invitrogen,
Carlsbad, CA, USA) at RT overnight and the biotinylated
secondary antibody (goat anti-rabbit, 1:1000, Jackson
Immuno Research, West Grove, PA, USA) at RT for 2 h.
Cells were visualized using the avidin–biotin–peroxidase
complex (Vector Laboratories, Burlingame, CA, USA),
followed by 3,30 -diaminobenzidine. Sections were mounted
on gel-coated slides, dehydrated and coverslipped with
Cytoseal (Richard-Allan Scientific, Kalamazoo, MI, USA).
BrdU quantification. BrdU-labelled cells were quantified ona Nikon (Melville, NY, USA) fluorescent microscope with a 40 objective. Using a modified stereological procedure,
BrdU þ cells in the subgranular zone and granule cell layer ofthe DG were counted manually from every sixth section, andan estimate of the total number of BrdU þ cells in the DG was
obtained by multiplying the average number of BrdU þ cells
per section by the number of 40-mm sections comprising theentire DG.12 For the 4-week survival group, BrdU þ /NeuN þcells were also counted manually and were expressed as aproportion of the total number of BrdU þ cells.
Morphological analysis. Morphological analysis of adultgenerated granule neurons was performed on an Olympus(Tokyo, Japan) light microscope using a  100 objective.
GFP þ neurons in the granule cell layer of the DG wereselected for analysis if they had at least one third-order
dendrite. Using NeuroLeucida software, the entire dendritic
arbor, including dendritic spines, was traced. A series ofconcentric spheres spaced 20 mm apart was centered on thesoma, and the number of times that each sphere wasintersected by a dendrite and the total dendritic length withineach sphere were quantified.13 Spine density was calculatedby dividing the spine number by dendritic length. Between one
to seven neurons were traced per mouse, and dependentmeasures were averaged within each mouse.
Statistical analysis. Data were subjected to either two-way
analysis of variance with group and sex as between-subject
factors or three-way analysis of variance with group andsex as between-subject factors and distance from soma as awithin-subject factor We found no significant effects involving
sex; therefore this factor was dropped from the analysis.
Results
To determine whether early life adversity reduces the numberof adult-generated cells in the DG, we injected adult mice with
BrdU to label proliferating cells. At 1 day after injection,maternally separated and control mice had similar numbers ofEarly adversity and adult neurogenesis
AT Leslie et al

3proliferating cells (Figure 1a; group effect: P40.05). However,at 4 weeks after injection, maternally separated mice had
fewer surviving cells (Figure 1b; group effect: F1,32 ¼ 7.88,
P ¼ 0.008) and a smaller proportion of surviving cells that
expressed NeuN, a marker of mature neurons (Figure 1c;

Figure 1 Adult-generated cells in the DG were labelled by injections of BrdU.
Maternal separation did not affect the number of proliferating cells 1 day after BrdU
injection (a), but reduced the number of cells that survived for 4 weeks (b) anddifferentiated into neurons (c).

group effect: F1,32 ¼ 6.90, P ¼ 0.013), indicating that maternal
separation persistently reduces the survival of adult-generated granule neurons in the DG.
Next, to examine whether early life adversity also affects thematuration of adult-generated neurons, we labelled proliferating cells in adult mice by microinfusion of a GFP-expressing
retrovirus into the DG. The robust and persistent expression of
GFP in the soma and processes allowed for the reconstruction
and detailed morphological analysis of infected neurons at alater time point. The complexity of dendritic arborization wasassessed by quantifying the number of dendritic intersections
and dendritic length as a function of distance from the soma
using Sholl analysis (Figures 2a and b).
We found that repeated and unpredictable periods ofseparation from the mother led to profound changes in thecomplexity of adult-generated granule neurons. Four weeks
post infection, new neurons in maternally separated mice
had fewer dendritic intersections (Figure 2c; group effect:
F1,8 ¼ 9.09,
P ¼ 0.017;
group  distanceinteraction:
F14,112 ¼ 3.73, Po0.001) and reduced dendritic length(Figure 2d; group effect: F1,8 ¼ 7.50, P ¼ 0.026; group 
distance interaction: F14,112 ¼ 2.71, P ¼ 0.002) compared with
control mice. Although spine density was unaffected (spines
per 10 mm; separation: 5.54±0.60; control: 5.93±0.24; groupeffect: P40.05), the reduction in dendritic complexity resulted
in fewer total numbers of spines per neuron (Figure 2e; groupeffect: F1,8 ¼ 5.59, P ¼ 0.046), suggesting that adult-generated granule neurons in maternally separated mice form fewer
synapses with incoming fibers.

Figure 2 Adult-generated neurons in the DG were labelled by a GFP-expressing retrovirus and visualized using 3,30 -diaminobenzidine staining 4 weeks after infection.
Representative images of adult-generated granule neurons from (a) control mice and (b) mice that were repeatedly and unpredictably separated from their mothers during thefirst 2 weeks of life (left:  20 magnification, scale bar ¼ 50 mm; right: manual tracings). Sholl analysis of adult-generated neurons revealed that maternal separation reduced
the complexity of dendritic arborization, as evidenced by (c) fewer intersections and (d) less dendritic length. (e) Representative images of dendritic spines (scale bar ¼ 3 mm)from control and maternally separated mice. Maternal separation reduced the total number of spines per neuron.
Translational Psychiatry

Early adversity and adult neurogenesis
AT Leslie et al

4Discussion
Previous studies in rodents report that early adversity, in theform of separation from the mother during the initial postnatal
weeks, alters the number and morphology of developmentally
generated DG neurons.14–17 Here, we show that the effects ofearly adversity on the generation and maturation of new DG
neurons persist long after the adverse events initially takeplace. Specifically, rodents that experience maternal separation early in life not only possess fewer new DG neurons
during adulthood,16,18–21 but also possess adult-generated
DG neurons with less complex dendritic arborization andfewer dendritic spines. Early adverse experiences, therefore,
can exert a long-lasting influence on the regulation ofneurogenesis during adulthood, potentially interfering withhippocampal function and leading to behavioral abnormalities
later in life. Indeed, rodents that experience maternal
separation early in life show several behavioral disturbances during adulthood, including cognitive deficits,16,19,22
decreased sociability,23,24 increased anxiety,22,25,26 and thepresence of depression- and schizophrenia-like behaviors,22,23,27,28 which is consistent with the possibility thatthe neurobiological consequences of early adverse experiences may contribute to the onset of psychiatric symptoms
later in life.
Our finding that the influence of early maternal separation
on adult neurogenesis is observable long after the adverse
experiences have taken place suggests that the effects ofearly adversity may be mediated through epigenetic modifications of DNA.29,30 Such modifications could result in persistentchanges in levels of stress hormones or neurotrophic factorsthat are known to influence the generation and growth of newneurons in the adult brain.31–33 For instance, adult rodents
that experienced maternal separation during the initial
postnatal weeks have higher circulating levels of corticosterone34–36 and reduced hippocampal levels of brain-derived
neurotrophic factor,21,35,37 nerve growth factor34 and neurotophin-3,34 thereby possibly resulting in reductions in thenumber and complexity of newly generated DG neurons.
Furthermore, maternal separation and poor maternal careearly in life have been found to produce changes in DNA
methylation38–40 that are passed onto the next generation ofoffspring,8 suggesting that the impact of early adversity on thebrain can persist throughout the lifespan and even into future
generations.
Whereas previous studies demonstrate that mutations ofgenes associated with increased risk of schizophrenia alter
the number and complexity of adult-generated neurons in theDG,3–5 we show here that early adversity, an environmental
risk factor, can produce similar changes. The abnormal
regulation of adult neurogenesis following early adverse
experiences could contribute to psychopathology by disrupting the balance between pattern separation and patterncompletion along the entorhinal cortex–DG–CA3 pathway,
leading to spurious associations, and hence the formation ofmemories with psychotic content.41 Our finding that neurogenesis during adulthood can be shaped by experiences earlyin life suggests that the abnormalities in adult neurogenesis
observed in individuals with schizophrenia, including fewer
new hippocampal cells in vivo42 and reduced connectivity
Translational Psychiatryof new neurons reprogrammed from fibroblasts in vitro,43
could arise from environmental influence alone or fromcomplex interactions of environmental factors with genetic
predisposition.
Conflict of interest
The authors declare no conflict of interest.

Acknowledgements. We thank Leonardo Restivo and Mika Yamamoto fortechnical assistance, and Sheena Josselyn for comments on the manuscript. This
work was supported by a grant from the Canadian Institutes of Health Research(CIHR, MOP86762) to PWF. KGA and SSDS were supported by fellowships from
CIHR. ADK was supported by a scholarship from the Natural Sciences andEngineering Research Council (NSERC). MS was supported by a fellowship fromthe Japanese Society for the Promotion of Science. MA-C was supported byscholarships from the Ontario Graduate Scholarship Program and the Hospital for
Sick Children.

1. Eisch AJ, Cameron HA, Encinas JM, Meltzer LA, Ming GL, Overstreet-Wadiche LS. Adult
neurogenesis, mental health, and mental illness: hope or hype? J Neurosci 2008; 28:
11785–11791.
2. Kempermann G, Krebs J, Fabel K. The contribution of failing adult hippocampal
neurogenesis to psychiatric disorders. Curr Opin Psychiatry 2008; 21: 290–295.
3. Duan X, Chang JH, Shayo G, Faulkner RL, Young Kim J, Kitabatake Y et al. DisruptedIn-Schizophrenia 1 regulates integration of newly generated neurons in the adult brain.
Cell 2007; 130: 1146–1158.
4. Pujades L, Gruart A, Bosch C, Delgado L, Teixeira CM, Rossi D et al. Reelin regulates
postnatal neurogenesis and enhances spine hypertrophy and long-term potentiation.
J Neurosci 2010; 30: 4636–4649.
5. Pieper AA, Xie S, Capota E, Estill SJ, Zhong J, Long JM et al. Discovery of aproneurogenic, neuroprotective chemical. Cell 2010; 142: 39–51.
6. van Os J, Kenis G, Rutten BPF. The environment and schizophrenia. Nature 2010; 468:
203–212.
7. Brown AS. The environment and susceptibility to schizophrenia. Progress Neurobiol 2011;
93: 23–58.
8. Franklin TB, Russig H, Weiss IC, Graff J, Linder N, Michalon A et al. Epigenetictransmission of the impact of early stress across generations. Biol Psychiatry 2010; 68:
408–415.
9. Weiss IC, Franklin TB, Vizi S, Mansuy IM. Inheritable effect of unpredictable maternal
separation on behavioral responses in mice. Front Behav Neurosci 2011; 5: 3.
10. Abbey H, Howard E. Statistical procedure in developmental studies on species withmultiple offspring. Dev Psychobiol 1972; 6: 329–335.
11. Tashiro A, Zhao C, Gage FH. Retrovirus-mediated single-cell gene knockout technique in
adult newborn neurons in vivo. Nat Protoc 2006; 1: 3049–3055.
12. Kee N, Teixeira CM, Wang AH, Frankland PW. Preferential incorporation of adultgenerated granule cells into spatial memory networks in the dentate gyrus. Nat Neurosci
2007; 10: 355–362.
13. Sholl DA. Dendritic organization in the neurons of the visual and motor cortices of the cat.
J Anat 1953; 87: 387–406.
14. Oomen CA, Soeters H, Audureau N, Vermunt L, van Hasselt FN, Manders EMM et al. Early
maternal deprivation affects dentate gyrus structure and emotional learning in adult female
rats. Psychopharmacology 2011; 214: 249–260.
15. Oomen CA, Girardi CEN, Cahyadi R, Verbeek EC, Krugers H, Joels M et al. Opposite
effects of early maternal deprivation on neurogenesis in male versus female rats. PLoS
ONE 2009; 4: e3675.
16. Oomen CA, Soeters H, Audureau N, Vermunt L, van Hasselt FN, Manders EMM et al.
Severe early life stress hampers spatial learning and neurogenesis, but improves
hippocampal synaptic plasticity and emotional learning under high-stress conditions inadulthood. J Neurosci 2010; 30: 6635–6645.
17. Nair A, Vadodaria KC, Banerjee SB, Benekareddy M, Dias BG, Duman RS et al. Stressorspecific regulation of distinct brain-derived neurotrophic factor transcripts and cyclic AMP
response element-binding protein expression in the postnatal and adult rat hippocampus.
Neuropsychopharmacology 2007; 32: 1504–1519.
18. Kikusui T, Ichikawa S, Mori Y. Maternal deprivation by early weaning increases
corticosterone and decreases hippocampal BDNF and neurogenesis in mice.
Psychoneuroendocrinology 2009; 34: 762–772.
19. Hulshof HJ, Novati A, Sgoifo A, Luiten PGM, den Boer JA, Meerlo P. Maternal separation
decreases adult hippocampal cell proliferation and impairs cognitive performance but has
little effect on stress sensitivity and anxiety in adult Wistar rats. Behav Brain Res 2011; 216:
552–560.

Early adversity and adult neurogenesis
AT Leslie et al

5
20. Mirescu C, Peters JD, Gould E. Early life experience alters response of adult neurogenesis
to stress. Nat Neurosci 2004; 7: 841–846.
21. Aisa B, Elizalde N, Tordera R, Lasheras B, Del Rio J, Ramirez MJ. Effects of neonatal
stress on markers of synaptic plasticity in the hippocampus: implications for spatial
memory. Hippocampus 2009; 19: 1222–1231.
22. Aisa B, Tordera R, Lasheras B, Del Rio J, Ramirez MJ. Cognitive impairment associated to
HPA axis hyperactivity after maternal separation in rats. Psychoneuroendocrinol 2007; 32:
256–266.
23. Veenema AH, Blume A, Niederle D, Buwalda B, Neumann ID. Effects of early life stress on
adult male aggression and hypothalamic vasopression and serotonin. Eur J Neurosci 2006;
24: 1711–1720.
24. Bouet V, Lecrux B, Tran G, Freret T. Effect of pre- versus post-weaning environmental
disturbances on social behaviour in mice. Neurosci Lett 2011; 488: 221–224.
25. Romeo RD, Mueller A, Sisti HM, Ogawa S, McEwen BS, Brake WG. Anxiety and fear
behaviors in adult male and female C57BL/6 mice are modulated by maternal separation.
Horm Behav 2003; 43: 561–567.
26. Wigger A, Neumann ID. Periodic maternal deprivation induces gender-dependent
alterations in behavioral and neuroendocrine responses to emotional stress in adult rats.
Physiol Behav 1999; 66: 293–302.
27. Ellenbroek BA, de Bruin NM, van Den Kroonenburg PT, van Luijtelaar EL, Cools AR. The
effects of early maternal deprivation on auditory information processing in adult Wistar rats.
Biol Psychiatry 2004; 55: 701–707.
28. Garner B, Wood SJ, Pantelis C, van den Buuse M. Early maternal deprivation
reduces prepulse inhibition and impairs spatial learning ability in adulthood: no further
effect of post-pubertal chronic corticosterone treatment. Behav Brain Res 2007; 176:
323–332.
29. Zhang T-Y, Meaney MJ. Epigenetics and the environmental regulation of the genome andits function. Annu Rev Psychol 2010; 61: 439–466.
30. Szyf M. The early life social environment and DNA methylation: DNA methylation mediating
the long-term impact of social environments early in life. Epigenetics 2011; 6: 971–978.
31. Mirescu C, Gould E. Stress and adult neurogenesis. Hippocampus 2006; 16: 233–238.
32. McEwen BS. Effects of adverse experiences for brain structure and function. Biol
Psychiatry 2000; 48: 721–731.
33. Alleva E, Francia N. Psychiatric vulnerability: suggestions from animal models and role ofneurotrophins. Neurosci Biobehav Rev 2009; 33: 525–536.

34. Marais L, van Rensburg SJ, van Zyl JM, Stein DJ, Daniels WMU. Maternal separation of rat
pups increases the risk of developing depressive-like behavior after subsequent chronic
stress by altering corticosterone and neurotrophin levels in the hippocampus. Neurosci Res
2008; 61: 106–112.
35. Lippmann M, Bress A, Nemeroff CB, Plotsky PM, Monteggia LM. Long-term behaviouraland molecular alterations associated with maternal separation in rats. Eur J Neurosci 2007;
25: 3091–3098.
36. Plotsky PM, Meaney MJ. Early, postnatal experience alters hypothalamic corticotropinreleasing factor (CRF) mRNA, median eminence CRF content and stress-induced releasein adult rats. Brain Res Mol Brain Res 1993; 18: 195–200.
37. Roceri M, Hendriks W, Racagni G, Ellenbroek BA, Riva MA. Early maternal deprivation
reduces the expression of BDNF and NMDA receptor subunits in rat hippocampus. Mol
Psychiat 2002; 7: 609–616.
38. Roth TL, Lubin FD, Funk A, Sweatt JD. Lasting epigenetic influence of early-life adversity
on the BDNF gene. Biol Psychiatry 2009; 65: 760–769.
39. Weaver ICG, Cervoni N, Champagne FA, D’Alessio AC, Sharma S, Seckl JR et al.
Epigenetic programming by maternal behavior. Nat Neurosci 2004; 7: 847–854.
40. Murgatroyd C, Patchev AV, Wu Y, Micale V, Bockmuhl Y, Fischer D et al. Dynamic DNA
methylation programs persistent adverse effects of early-life stress. Nat Neurosci 2009; 12:
1559–1566.
41. Tamminga CA, Stan AD, Wagner AD. The hippocampal formation in schizophrenia. Am J
Psychiatry 2010; 167: 1178–1193.
42. Reif A, Fritzen S, Finger M, Strobel A, Lauer M, Schmitt A et al. Neural stem cellproliferation is decreased in schizophrenia, but not in depression. Mol Psychiatry 2006; 11:514–522.
43. Brennard KJ, Simone A, Jou J, Gelboin-Burkhart C, Tran N, Sangar S et al. Modelling
schizophrenia using human induced pluripotent stem cells. Nature 2011; 473: 221–225.

Translational Psychiatry is an open-access journal
published by Nature Publishing Group. This work islicensed under the Creative Commons Attribution-Noncommercial-No
Derivative Works 3.0 Unported License. To view a copy of this license,
visit http://creativecommons.org/licenses/by-nc-nd/3.0/

Translational Psychiatry