Genetic Models of Schizophrenia

118 Pages·2009·14.38 MB·English

by  Sawa Akira (Eds.)

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List of Contributors
A.F.T. Arnsten, Department of Neurobiology, Yale Medical School, New Haven, CT, USA
N.J. Brandon, Wyeth Research, Department of Neuroscience, NJ, USA
R. DiLeone, Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
R. Fukumura, RIKEN BioResource Center, Tsukuba, Ibaraki, Japan
K. Furukubo-Tokunaga, Graduate School of Life and Environmental Sciences, University of Tsukuba,
Tennodai, Tsukuba, Japan
Y. Gondo, RIKEN BioResource Center, Tsukuba, Ibaraki, Japan
A.Hayashi-Takagi,DepartmentofPsychiatryandBehavioralSciences,JohnsHopkinsUniversitySchool
of Medicine, Baltimore, MD, USA
H. Jaaro-Peled, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School
of Medicine, Baltimore, MD, USA
A. Kamiya, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of
Medicine, Baltimore, MD, USA
C. Kellendonk, Department of Psychiatry, Department of Pharmacology, New York, NY, USA
M.P. Kelly, Wyeth Research, Department of Neuroscience, NJ, USA
J.A.Morris,PrograminHumanMolecularGenetics,DepartmentofPediatrics,FeinbergSchoolofMedicine,
Children'sMemorialResearchCenter,NorthwesternUniversity,Chicago,IL,USA
M.V. Pletnikov, Departments of Psychiatry and Neuroscience, Johns Hopkins University School of
Medicine, Baltimore, MD, USA
A.J. Ramsey, University of Toronto, Department of Pharmacology and Toxicology, Toronto, ON,
Canada
A. Sawa, Departments of Psychiatry and Neuroscience, Johns Hopkins University School of Medicine,
Baltimore, MD, USA
A.J. Seshadri, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of
Medicine,Baltimore,MD,USA
A.A. Simen, Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
K.Talbot,CenterforNeurobiologyandBehavior,DepartmentofPsychiatry,UniversityofPennsylvania,
Philadelphia, PA, USA
v
Preface
This volume focuses on how genetic models for schizophrenia, that is, manipulation in genetic
susceptibility factors for the disease, have potential in opening a new window of better understanding of
etiology-relevantmechanisms.Inaddition,thesemodelscanprovideapromisingnovelplatformfordrug
screening toward the treatment of the disease. In particular, this volume introduces novel techniques to
generatemousemodelsforschizophreniaandreferstotheuseofdrosophila,zebrafish,andprimatesfor
modelingthedisease,inadditiontorodents.Representativemodelsforschizophreniacurrentlyavailable
in mice are also systematically introduced, which include mice with modulation of neurotransmission
(glutamate and dopamine receptors, respectively) and key intracellular signaling (Disrupted in
Schizophrenia, Dysbindin, and phosphodiesterase) possibly associated with neurotransmission, together
with genetic support.
Key features
(cid:1)
Leading authors describe the most updated strategies to address genetic manipulation for modeling
schizophrenia, including their advantages and limitations.
(cid:1) Investigatorsworkingonvariouslevelsoforganisms/animalsfromdrosophila,zebrafish,rodents,to
primates discuss the potential to generate genetic models for schizophrenia toward mechanistic
understanding of the disease as well as translational use, such as drug screening.
(cid:1) Leading authors of this field introduce representative animal models for schizophrenia at present.
Akira Sawa
vii
A.Sawa(Ed.)
ProgressinBrainResearch,Vol.179
ISSN0079-6123
Copyrightr2009ElsevierB.V.Allrightsreserved
CHAPTER 1
Genetic animal models for schizophrenia:
advantages and limitations of genetic manipulation
fi
in drosophila, zebra sh, rodents, and primates
(cid:1)
Akira Sawa
DepartmentsofPsychiatry andNeuroscience, Johns HopkinsUniversity School ofMedicine,Baltimore, MD, USA
Abstract: Schizophrenia is a debilitating mental illness in which major initial risks of the disease during
neurodevelopment may disturb postnatal brain maturation, which results in onset after puberty. Family,
twin, and adoption studies have suggested an important role for genetic factors in the etiology of
schizophrenia.Toaddresstheetiology-associatedmechanismsanddiseasecourse,useofgeneticmodels,
that is, manipulation of genetic susceptibility factors, is currently considered to be a powerful tool for
biological studies. In this manuscript, advantages and possible limitations in manipulating genetic
susceptibility factors for schizophrenia toward modeling the disease are discussed. In addition to mouse
models, the potential to use drosophila, zebrafish, and primates is underscored.
Keywords: schizophrenia; gene; animal model
Introduction 2009). In physical disorders and other brain
disordersstudiedintheareaofneurology,genetic
Schizophrenia is a debilitating mental illness in factors have been utilized to build animal models
which genetic factors are known to play a role. for diseases (Wong et al., 2002). In analogy to
None of the factors causes the disease by itself, these successfulpreceding works, many investiga-
butacombinationofgeneticfactorstogetherwith torsarecurrentlytryingtodevelopgeneticmodels
environmental impact results in manifestation for schizophrenia. In this chapter, the advantages
of the symptoms (Sawa and Snyder, 2002). For and limitations of genetic models for schizophre-
the past 10 years, promising genetic susceptibility nia will be overviewed.
factors for schizophrenia have been found
(HarrisonandWeinberger,2005).Wholegenome
association studies and work on copy number Advantage of genetic animal models
variations are further discovering new suscept-
ibility factors (Cichon et al., 2009; Williams et al.,
Manyepidemiologicalstudieshavesuggestedthat
initial brain insults associated with schizophrenia
occur mainly during early neurodevelopment.
(cid:1) Nonetheless, the real onset of the disease is in
Correspondingauthor.
young adulthood. These observations indicate
Tel.:[phone];Fax:[phone];
E-mail:[email protected] that postnatal brain maturation may play an
DOI:10.1016/S0079-6123(09)17901-3 3
4
important role in the pathology of schizophrenia the fast spiking interneurons, which is known
(Jaaro-Peled et al., 2009). in both autopsied brains from patients with
Administration of compounds that can induce schizophrenia and some genetic animal models
psychosis in humans, such as phencyclidine, into for schizophrenia (Hikida et al., 2007; Lisman et
adult animals has been widely used for modeling al.,2008;Shenetal.,2008).Itmaybeimportantto
schizophrenia(Mourietal.,2007).Althoughthese cultivate more varieties of molecular biomarkers
models are useful in recapitulating the pathophy- for schizophrenia. For this purpose, use of
siology of schizophrenia in part, it is very difficult human-derived neurons, such as olfactory neu-
to mimic the long-term pathological changes rons obtained via nasal biopsy and induced
leading from disease-associated insults (triggers, pluripotent stem cell-originated neurons, may be
risk factors) during pre- and peri-natal stages to usefulresourcesinthefuture(SawaandCascella,
the onset of the disease in young adulthood. To 2009; Takahashi et al., 2007).
overcome this limitation, introduction of brain
lesions by toxins during early development has
been considered as an alternative strategy for Possible limitations of genetic animal models
modeling schizophrenia (Lipska et al., 1993;
Talamini et al., 1998). A major concern in this As described above, schizophrenia is not caused
second strategy is that these lesions may not by any single factor; instead, a combination of
reflect the disease etiology. Therefore, genetic several genetic and environmental factors results
models for schizophrenia, including genetically in the disease. A major limitation in most
engineered mice in which genetic susceptibility technologies for genetic manipulation in animals
factor(s) for the disease is (are) modulated, are is that only one gene can be modified per
currently underscored to be a promising novel generation, except by utilizing laborious
methodology. cross-breeding experiments, whereas modulation
Use of genetic model animals has at least two of more than one gene may be expected to more
significant advantages. First, as described above, faithfully mimic the etio-pathological condition
these will contribute to understanding of the of schizophrenia. How can we overcome this
pathologyofthedisease,includingthecourseand dilemma? Mouse models generated by in utero
mechanismsrelevanttodiseaseetiologies.Indeed, gene transfer or by stereotaxic injection of
major genetic susceptibility factors for schizo- virus-mediated expression or RNAi constructs,
phrenia play key roles during early development, through which we can manipulate expression of
which suggests that these factors may be tightly more than one gene simultaneously, may open a
associated with the cause of the disease. Second, new window toward overcoming this limitation
such models can be utilized for translational (Kamiyaetal.,2008).Althoughthesemicearenot
means, such as compound screening for future genetic models in a strict sense (because the
therapeuticstrategytowardschizophrenia.There- manipulationisnotheritable),thesestrategiesare
fore,highthroughputreadoutsthatreflecthuman veryimportanttomodelschizophreniabyutilizing
pathology and phenotypes may be expected in informationaboutgeneticsusceptibilityfactors.
animal models. Are behavioral assays, however, Theotherdifficultyinusinggeneticinformation
the most appropriate readouts to evaluate these inmodelingschizophreniaisthatwedonotknow
models?IngeneticanimalmodelsforAlzheimer's how disease-associated genetic variations play
disease, senile plaques or b-amyloid plaques are rolesinthepathology.Itisunlikelythatcomplete
used as a major readout to evaluate the models. loss-of-function and simple gain-of-function are
Considering this successful precedence, it may be elicited by such genetic variations. Instead,
importanttoconsider objective biomarkersinthe impairment of specific isoform(s) of the suscept-
study of animal models for schizophrenia. One ibility factors or partial loss-of-function is fre-
promising approach may be to utilize decrease in quently suggested to be a mechanism (Tan et al.,
immunoreactivity of parvalbumin, a marker for 2007). In this sense, conventional knockout or
5
transgenic mice may have some limitations in in genetic susceptibility factors for schizophrenia,
modeling the disease. Techniques that introduce are discussed. Many types of animals and organ-
mutationscausingminorfunctionalimpairmentsin isms, such as rodents (mice and rats), drosophila,
the target genes or modulations of gene expres- zebrafish,andprimates,canpotentiallybeutilized
sioninacontext-dependentmannermaybeuseful toward the goal.
to address this issue. Therefore, models with
genetic mutations induced by chemical mutagens Acknowledgments
and conditional/inducible genetic models are
considered to be promising (Gondo, 2008; Li
IthankSauravSeshadriforcriticalreadingofthis
et al., 2007; Pletnikov et al., 2008).
manuscript. I appreciate Yukiko Lema for orga-
nizing the figures and manuscript. This work is
supported by US Public Heath Service Grant
Potential in using drosophila, zebrafish, and
MH-069853, Silvio O. Conte Center grant MH-
primates as models for schizophrenia
084018, MH-088753, and foundation grants from
Stanley, RUSK, as well as NARSAD.
Two major goals in building model organisms/
animals for schizophrenia are to address molecu-
lar mechanisms and to utilize them for transla-
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A.Sawa(Ed.)
ProgressinBrainResearch,Vol.179
ISSN0079-6123
Copyrightr2009ElsevierB.V.Allrightsreserved
CHAPTER 2
Animal models for schizophrenia via in utero gene
transfer: understanding roles for genetic
susceptibility factors in brain development
(cid:1)
Atsushi Kamiya
DepartmentofPsychiatry andBehavioral Sciences,Johns Hopkins UniversitySchool ofMedicine,
Baltimore, MD,USA
Abstract: Geneticdisturbancesofbraindevelopmentmayunderliethepathophysiologyofschizophrenia.
Recentadvancesinmolecularneurobiologysuggestthatsomegeneticriskfactorsforschizophreniahave
multiplerolesinvariousbrainregionsdependingonthedevelopmentalstage.Furthermore,thesefactors
are likely to act synergistically or epistatically in common molecular pathways, possibly contributing to
disease pathology. Thus, a technique that can manipulate the expression of more than one gene
simultaneouslyinanimalmodelsisnecessarytoaddresssuchmolecularpathways.Toproducesuchanimal
models,inuterogenetransfertechniqueisoneusefulmethod.Giventhatplasmid-basedcell-type-specific
andinduciblegeneexpressionsystemsarenowavailable,combiningthesetechnologiesandinuterogene
transfer opens a new window to examine the functional role of genetic risk factors for schizophrenia by
conductingmultiple-genetargetinginaspatialandtemporalmanner.Theutilityofanimalmodelsproduced
byinuterogenetransferwillalsobeexpectedtobeevaluatedintermsoffunctionalandbehavioraloutcomes
afterpuberty,whichmaybeassociatedwithschizophreniapathology.
Keywords: in utero gene transfer; brain development; animal model; genetic factor; schizophrenia
Introduction disturbances in many brain regions, including the
cerebral cortex, hippocampus, thalamus, and
Disturbancesinneuronalcircuit formation during amygdala in patients with schizophrenia. This
brain development are believed to underlie the concept is further supported by the fact that
pathology of schizophrenia (Lewis and Levitt, many genetic risk factors for schizophrenia, such
2002; Rapoport et al., 2005). Consistent with this as Disrupted-in-Schizophrenia-1 (DISC1) and
notion, accumulating evidence from neuropatho- Neuregulin-1,playkeyrolesinneurodevelopment
logical examinations and brain imaging studies (Harrison and Weinberger, 2005; Jaaro-Peled
suggest a variety of anatomical and functional et al., 2009; Owen et al., 2005). Thus, it is impor-
tant to examine how disturbances of such risk
factors impact neuronal circuit formation during
(cid:1) brain development. Some of them are likely to
Correspondingauthor.
function not only in early developmental pro-
Tel.:[phone];Fax:[phone];
E-mail:[email protected] cesses (i.e. pre- and perinatal stages), but also in
DOI:10.1016/S0079-6123(09)17902-5 9
10
Fig.1. Inuterogenetransferforgenetargetingindevelopingbrain.(A)Schematicrepresentationofinjectionofplasmidconstructs
into lateral ventricle following by their delivery into ventricular zone via electroporation with forceps-type electrodes. (B)
RepresentativecoronalimagesofbrainswithGFPexpressionatpostnatalday1(P1)afterintroductionofGFPexpressionconstruct
atembryonicday15(E15).MostGFP-positivecellsareintheuppersideofcorticalplate(CP)whichformslayerII/IIIofcerebral
cortex (upper panels, low magnification; bottom panels, high magnification). CC, cerebral cortex; MZ, marginal zone; SVZ,
subventricularzone;VZ,ventricularzone.Red,Nucleus.Scalebars,100mm.
late developmental stages (i.e. childhood and In this respect, the in utero gene transfer
adolescence) and even in adulthood when their technique is a promising methodology. This
roles may or may not be the same as those in technique allows for the expression of more than
developmental stages. Interestingly, these factors one target gene to be modulated by introduction
likelyactsynergisticallyorepistaticallyincommon ofexpressionand/orshorthairpinRNA(shRNA)
molecular pathways during brain development, constructs in the developing brain. In this techni-
perhapsleadingtosusceptibilityforschizophrenia que, plasmid expression vectors are injected into
by shared pathological mechanisms (Harrison the lateral ventricles of the embryonic brain
and Weinberger, 2005; Jaaro-Peled et al., 2009; through the uterine wall and are introduced into
Owen et al., 2005). Therefore, a technique that the ventricular zone by electroporation (Tabata
canmanipulateexpressionofmorethanonegene and Nakajima, 2001) (Fig. 1). Since the electro-
simultaneously in a spatial and temporal manner porated embryos develop normally in utero, we
is necessary to address such molecular pathways, can characterize them at any developmental
whichmaycontributetothediseasepathology. stages, and even at the adult stage. There are
11
Fig.2. Region-specificgenetargetingbyinuterogenetransfer.Schematicrepresentationofinuterogenetransferbychangingthe
directionofelectroporationforgenetargetingintospecificregions.(A)Neocorticalneuroepitheliumistargetedbydorsallateral
placementofthepositive(+)electrode.(B)Ganglioniceminenceistargetedbyventrallateralplacementofthepositiveelectrodeat
about301outwardanglefromthehorizontalplane.(C)Lateroventralpallialneuroepitheliumistargetedbyventrallateralplacement
ofthepositiveelectrodeatabout151outwardanglefromthehorizontalplane.(D)Ammonicneuroepitheliumistargetedbydorsal
lateral placement of the positive electrode on side without plasmids injection. NC, neocortex; GE, ganglionic eminence; PIR,
piriformcortex;H,hippocampus.
several advantages in using this method, in factors in molecular pathways underlying the
comparison with conventional genetically engi- pathologyofschizophreniainthecontextofbrain
neeredanimalmodels.First,genetargetingcanbe development.
conducted in specific cell types in restricted brain
regions without causing embryonic lethality that
may result from the lack of a crucial molecule Region-specifictargetingbyinuterogenetransfer
during development. Second, we can save the
time required to produce animal models, because The proper development of prefrontal cortex,
themethodismuchsimplerandquicker.Further- togetherwiththesubcorticalregionsofthelimbic
more,thespecificfunctionalinteractionbetweena system,includingthehippocampusandamygdala,
target molecule and its binding partner(s) can be is important for mediating higher brain function-
examined through co-electroporation of multiple ing, such as cognition, memory, and emotion.
constructs. Specifically, rescue experiments may Each of these regions is implicated in the
provide crucial information regarding the impact pathophysiology of schizophrenia (Harrison and
of specific allelic variants that increase risk to Weinberger, 2005). Although many types of
disease. In this chapter, we overview the current genetically engineered animal models including
progress of this technology and discuss its inducible and conditional systems have been
feasibility for addressing the role of genetic risk established, region-specific gene targeting has not