European Journal of Pharmacology 719 (2013) 112–116

Contents lists available at ScienceDirect

European Journal of Pharmacology

0014-29http://d

n CorrMedicalVanvite

E-m

journal homepage: www.elsevier.com/locate/ejphar

Review

Mutations of the synapse genes and intellectual disability syndromes

Chiara Verpelli a, Caterina Montani a, Cinzia Vicidomini a, Christopher Heise a, Carlo Sala a,b,n

a CNR Institute of Neuroscience and Department of Medical Biotechnology and Translational Medicine, University of Milan,Via Vanvitelli 32, 20129 Milano, Italyb Neuromuscular Diseases and Neuroimmunology, Neurological Institute Foundation Carlo Besta, Via Celoria 11, 20133 Milan, Italy

a r t i c l e i n f o

Article history:Received 6 May 2013Received in revised form4 June 2013Accepted 1 July 2013Available online 17 July 2013

Keywords:Intellectual disabilityBrain synapsesDendritic spineAutism

99/$ - see front matter & 2013 Elsevier B.V. Ax.doi.org/10.1016/j.ejphar.2013.07.023

esponding author at: CNR Institute of NeurBiotechnology and Translational Medicine

lli 32, 20129 Milano, Italy. Tel.: +39 02 503170ail address: c.sala@in.cnr.it (C. Sala).

a b s t r a c t

Intellectual disability syndromes have been found associated to numerous mutated genes that code forproteins functionally involved in synapse formation, the regulation of dendritic spine morphology, theregulation of the synaptic cytoskeleton or the synthesis and degradation of specific synapse proteins.These studies have strongly demonstrated that even mild alterations in synapse morphology andfunction give rise to mild or severe alteration in intellectual abilities. Interestingly, pharmacologicalagents that are able to counteract these morphological and functional synaptic anomalies can alsoimprove the symptoms of some of these conditions. This review is summarizing recent discoveries on thefunctions of some of the genes responsible for intellectual disability syndromes connected with synapsedysfunctions.

& 2013 Elsevier B.V. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1122. Mutations in the synaptic scaffold proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

2.1. Mutations and deletions in the SHANK gene family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1132.2. The MAGUK family of proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

3. Mutations in the X chromosome genes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1133.1. The IL1RAPL1 gene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1133.2. The oligophrenin-1 gene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1143.3. The TM4SF2 gene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

4. Conclusions and prospectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Aknowledgmets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

1. Introduction

Psychiatric and neurological diseases are often characterized bythe occurrence of aberrant synaptic formation, function andplasticity, or malformed dendritic spine (Blanpied and Ehlers,2004) and it is now clear that an accurate control of synapticformation and maturation is critical for the development of acorrect active neuronal network essential for all brain functions.

ll rights reserved.

oscience and Department of, University of Milan, Via96; fax: +39 02 0250317132.

Intellectual disability (ID) is one of the most common neuro-developmental disorders; intelligence quotient of patients affectedby ID is about 70 or below and deficits in behavior related toadaptive functioning including autism spectrum disorders (ASD)are often exhibited by these patients.

It has been demonstrated that 25% of ID patients are carryinggenetic mutations (Rauch et al., 2006) while in up to 60% of casesthe pathogenetic mechanisms have been not identified.

More than a few single-genes causing syndromic or nonsyn-dromic ID have been recognized over the past 20 yr. Interestinglyseveral of these genes are located on the chromosome X and areresponsible for X-linked intellectual disabilities (XLID). Fascinat-ingly more than 50% of the ID-gene codifies for proteins clearlylocated in the pre- or post-synaptic compartments and emerge to

C. Verpelli et al. / European Journal of Pharmacology 719 (2013) 112–116 113

be implicated in synaptic functions by regulating synapse forma-tion, actin cytoskeleton rearrangement, or synaptic plasticity(Ropers and Hamel, 2005).

The synapse-related proteins associated with ID can be sepa-rated into two groups, one that localizes fully at synapses andwhose deletions and mutations directly impede with synapticformation, and a second cluster that indirectly controls neuronaldevelopment and synapse formation by regulating synthesis anddegradation of major synaptic proteins or the synaptic actincytoskeleton assembly or disassembly. In this review we willdescribe some molecular mechanisms by which dysfunctions inseveral of these proteins contribute to ID.

2. Mutations in the synaptic scaffold proteins

2.1. Mutations and deletions in the SHANK gene family

A partial and variable in size distal deletion of chromosome 22involves an important region that contains SHANK3 gene whichcodifies the large postsynaptic scaffold protein Shank3. Thisdeletion causes in humans the Phelan-McDermid syndrome(PMS, also called 22q13.3 deletion syndrome) which is character-ized by strong intellectual impairment, absent or delayed speech,autistic-like behavior, hypotonia, and mild dysmorphic features(Bonaglia et al., 2001; Manning et al., 2004; Phelan et al., 2001;Wilson et al., 2003).

Thus SHANK3 haploinsufficiency is considered to be the majorcause of the neurological symptoms of PMS, even if other genesmay also be missing by the chromosomal deletion especially whenthe deletion is particularly large (Bonaglia et al., 2001; Delahayeet al., 2009; Durand et al., 2007; Wilson et al., 2003). In reality, anumber of de novo mutations in SHANK3 (Durand et al., 2007;Gauthier et al., 2009; Moessner et al., 2007), but also in the othermember of the SHANK family, SHANK1 (Sato et al., 2012) andSHANK1 (Berkel et al., 2010) have been identified in individualswith ASD and ID. All these data strongly suggest that deletion andmutations in the SHANK genes are always associated to severecognitive diseases.

The functions of the three SHANK genes have been recentlywell studied using genetic mutations in mice. The first describedmouse was the SHANK1 full knock out, that showed small dendriticspines, weakened synaptic transmission, enhanced learning (Hunget al., 2008), and defects in social communication (Wöhr et al.,2011). For SHANK3 a number of mutant mice have been recentlydescribed in order to highlight the importance of Shank3 haploin-sufficiency in the pathogenesis of ID and Phelan-McDermid syn-drome (Bozdagi et al., 2010; Peça et al., 2011; Wang et al., 2011). TheSHANK3 gene has several splice variants and consequent specificknocks have been created. The genetic deletion of two majorSHANK3 splice variants causes self-injurious repetitive groomingand alterations in social relations correlating with major modifica-tion in striatal synapses and cortico-striatal circuits, but not inhippocampal synapses, suggesting that the remaining SHANK3splice variant(s) may be enough to preserve normal synapseorganization and function in hippocampus (Peça et al., 2011). Inother two independent mice, where only longest splice variant hasbeen deleted, defects in social behavior, alterations in learning, inmemory formation and in synaptic transmission have beendescribed (Bozdagi et al., 2010; Wang et al., 2011). These animalshad markedly impaired basal synaptic transmission in CA3–CA1connections, reduced GluR1 clusters and protein levels in thehippocampus, and an altered activity-dependent AMPAR synapticplasticity (Bozdagi et al., 2010; Wang et al., 2011).

In our laboratory we recently knocked down all major Shank3splice variants in rodent neuronal cultures by RNA interference

(shRNA) and demonstrated that Shank3 absence in hippocampalcells specifically reduced the expression of mGlu5 receptors, andalso impaired DHPG-induced phosphorylation of ERK1/2 and CREB(Verpelli et al., 2011). We thus propose that mGlu5-dependentsynaptic plasticity is altered in absence of Shank3.

Finally, similarly to SHANK3, also the SHANK2 full knockoutmice shows abnormalities in behavior tests, impairment in socialactivities, hyperactivity, and defects in synaptic transmission(Bockers et al., 2004; Schmeisser et al., 2012; Won et al., 2012).

Altogether, these studies show that in mice mutations in theSHANK genes cause alterations in both synaptic morphology andsignalling and behavior characteristics, therefore, these mice are agood animal model to study ASD and ID although the specific roleof the various splice variants of the SHANK1–3 genes remains tobe determined with more sophisticated genetic experiments.

2.2. The MAGUK family of proteins

PSD-95, codifies by DLG4 gene in humans, is the most abundantscaffold protein at the PSD that belongs to the MAGUK family ofproteins. Although polymorphisms and mutations have beenextensively searched in DLG4 in association with neurodevelop-mental pathologies, only one major study suggests, up to now, anassociation between a DLG4 gene variation and ASD and Williamssyndrome (Feyder et al., 2010). A second study demonstrated anhaplotype derived from 2 polymorphic markers at the corepromoter region of DLG4 gene has been associated to schizophre-nia (Cheng et al., 2010).

On the contrary, DLG3 – the human gene that encodes forsynapse-associated protein 102 (SAP102) – is clearly linked with ID(Tarpey et al., 2004; Zanni et al., 2010). Some mutations identifiedin this gene cause premature stop codons within or before thethird PDZ domain. These mutations damage the ability of theprobable truncated SAP102 protein to bind with the NMDAreceptors and other proteins regulating in NMDA receptors signal-ling pathways (Chen et al., 2011).

3. Mutations in the X chromosome genes

The majority of the XLID are attributable to the Fragile X andRett syndromes, however deletions and mutations of several othergenes on chromosome X have been found strongly associated withID. Mutations of the NLGN3 and NLGN4 genes (Jamain et al., 2003)were the first to be clearly associated with alterations in synapticfunction.

Neuroligin proteins, originally identified as binding partners ofneurexins, are the prototype of the synaptic adhesion moleculesthat regulate and promote synaptogenesis in the brain. Theneuroligins/neurexins association forms the trans-synaptic com-plex which is important for both excitatory and inhibitory synapseformation in brain (Südhof, 2008). In the recent years several otherXLID genes have been associated to synaptic function and indeed ithas been estimated that about 50% of the XLID gene codifies forsynaptic proteins (Laumonnier et al., 2007). Here we will describethe function of some of these genes.

3.1. The IL1RAPL1 gene

A number of mutations in the interleukin-1 receptor accessoryprotein-like 1 gene (IL1RAPL1) have been found in patients withcognitive impairments ranging from nonsyndromic ID to ASD(Bhat et al., 2008; Carrie et al., 1999; Franek et al., 2011; Pitonet al., 2008). The IL1RAPL1 protein belongs to a new Toll/IL-1receptor family and shares 52% homology with the IL-1 receptoraccessory protein (IL-1RacP) and it is structurally formed by three

C. Verpelli et al. / European Journal of Pharmacology 719 (2013) 112–116114

extracellular Ig-like domains, a transmembrane domain, and anintracellular Toll/IL-1R homology domain (TIR domain). In contrastto the other family members, IL1RAPL1 has 150 additional aminoacids at the C-terminus, that interact with the neuronal calciumsensor-1 (Bahi et al., 2003), thus regulating type voltage-gatedcalcium channel activity in PC12 cells and in neurons (Gambinoet al., 2007).

Our laboratory recently showed that IL1RAPL1 is a postsynapticproteins that specifically binds to postsynaptic density protein 95(PSD-95) and regulates its phosphorylation and synaptic associa-tion by activating the c-Jun terminal kinase (JNK) (Pavlowsky et al.,2010).

We also showed that the extracellular domain of IL1RAPL1induces excitatory synapse formation by binding the receptortyrosine phosphatase δ (PTPδ), which is localized at the presynap-tic terminal, while the TIR domain binds to a postsynaptic RhoGAP,called RhoGAP2, and regulates dendritic spine formation (Valnegriet al., 2011b). Interestingly it was also demonstrated that theextracellular domain of IL1RAPL1 interacts only with particularsplice variants of PTPδ (Yoshida et al., 2011). All these findingssuggest that the IL1RAPL1 complex, similarly to the neuroligin/neurexin complex, regulates trans-synaptic signalling that inducesexcitatory synapse and dendritic spine formation in brain.

All this data strongly suggests that most of the synapticadhesion molecules found associated with ID regulate excitatoryand inhibitory synapse formation and the consequential functionalalteration or reduction in number of excitatory or inhibitorysynapses arising from their mutations may alter the balancebetween excitatory and inhibitory synapses. This induces a generaldisorder within neuronal circuits and may be the direct cause of IDand ASD in humans. Indeed, even small changes in the expressionand function of these synaptic adhesion proteins can provokemajor alterations in synaptic connectivity, resulting in cognitivedamages.

3.2. The oligophrenin-1 gene

Mutations or deletions in the synaptic RhoGTPase-activatingprotein oligophrenin-1 are clearly associated to some forms ofXLID (Nadif Kasri and Van Aelst, 2008) indicating that alterationsin the function of member A of the Ras homologue gene family(RhoA) are implicated in ID.

Oligophrenin-1 is a negative regulator of RhoA, Rac and Cdc42and also interacts with the postsynaptic adaptor protein Homer(Govek et al., 2004). Knockdown of oligophrenin-1 in CA1 pyr-amidal neurons considerably reduces spine length and this effectis mimicked by a constitutively active form of RhoA and can berescued by the overexpression of constitutively active RhoA whichinduces to an inhibition of the RhoA effector Rho-kinase (ROCK1)(Govek et al., 2004).

Taking into consideration the central role of ROCK1 in actinremodelling, these results strongly propose that RhoA regulatesthe actin cytoskeleton of spines, perhaps through modulation onthe LIM kinase, myosin light chain (MLC), or MLC phosphataseactivity (Govek et al., 2004; Nadif Kasri and Van Aelst, 2008). Thus,loss of suppression of RhoA and ROCK1, in absence of oligophre-nin-1, induces to alterations of the actin cytoskeleton, follow-on inmodification of morphology of dendritic spine.

Learning impairment in oligophrenin-1-deficient mice has beendemonstrated by Khelfaoui et al. (Khelfaoui et al., 2007). Indeedanother study showed that oligophrenin-1 localizes to dendritic spinesafter synaptic NMDA stimulation, where it forms a complex withAMPA receptors and selectively increases AMPA-receptor-mediatedtransmission and dendritic spine volume by stabilising those receptorsat synapses (Nadif Kasri et al., 2009). The ability of oligophrenin-1 tostabilize AMPA receptors in synapses is also indicated by a reduced

number and a reduced activity of these receptors in the oligophrenin-1 KO mice. Interestingly this deficiency is rescued by impairing AMPAreceptor endocytosis which also indicates a correlation betweenoligophrenin-1/RhoA signalling and endocytosis of AMPA receptor atsynapses (Khelfaoui et al., 2009).

A new and very interesting role of oligophrenin-1 in regulatingthe activity of the circadian clock protein Rev-erbα has recentlybeen shown, suggesting that the pathogenesis of intellectualdisability could be related to the interaction between synapticactivity and circadian oscillators (Valnegri et al., 2011a). In additionto its role at postsynaptic sites, oligophrenin 1 also has a probablya presynaptic function by acting as a modulator of synaptic vesicleaccessibility and by acting as regulator of vesicle pool dynamics.Indeed, a reduced expression of oligophrenin-1 has been reportedto induce synaptic vesicle endocytosis in culture neurons(Khelfaoui et al., 2009). Powell et al. recently showed thatoligophrenin-1-deficient mice have alterations in the number ofvesicles in the readily releasable pool and also have a changed ofsecretory vesicles availability in some brain synapses (Powell et al.,2012).

Thus, alterations in oligophrenin-1 expression result in vari-ous deficits of synaptic function and plasticity that depend onoligophrenin-1 presence in both the pre- and postsynaptic compart-ments.

3.3. The TM4SF2 gene

The TM4SF2 gene codifies for the tetraspanin 7 (TSPAN7)protein, which is a member of the tetraspanin superfamily ofevolutionarily-conserved membrane proteins that associate dyna-mically with numerous partner proteins in the so called tetraspanin-enriched microdomains (TEMs) of the plasma membrane (Boucheixand Rubinstein, 2001). Different tetraspanins play essential roles indifferent cell functions including oocytes during fertilization, fungiduring leaf invasion, Drosophila embryos during neuromuscularsynapse formation, T and B lymphocyte activation, retinal degenera-tion, and brain function (Hemler, 2005).

Tetraspanins proteins are formed by four transmembranedomains, a short extracellular loop (EC1), a very short intracellularloop (IL), a longer extracellular loop (EC2), and short N- andC-terminal cytoplasmic tails. The variable region of the EC2domain contains several protein interaction sites (Berditchevski,2001). Interestingly the N and C termini of individual tetraspaninsare highly conserved across vertebrates, but differ among eachtetraspanin with the C-terminal tail is particularly divergent(Hemler, 2008). This indicates that, even with their short lengths,the N and C termini have specific functions, including associationto cytoskeletal and signalling molecules.

The molecular functions of tetraspanins proteins are onlypartially known. Some data suggest that tetraspanins regulatethe signalling, trafficking and biosynthetic processing of associatedproteins (Hemler, 2008), and may connect the extracellulardomain of α chain integrins with intracellular signalling molecules,including PI4K and PKC, both of which regulate cytoskeletalarchitecture (Chavis and Westbrook, 2001; Hemler, 1998; Yauchet al., 2000). Interestingly, the treatment with kainic acid up-regulates TM4SF2 mRNA, suggesting that TSPAN7 is involved insynaptic plasticity (Boda et al., 2002).

Mutations in the TM4SF2 gene, including TM4SF2 inactivation byX;2 balanced translocation, a premature stop codon TGA (gly218-to-ter) (Zemni et al., 2000), and a 2-bp deletion (564 delGT) resulting in apremature stop codon at position 192 (Abidi et al., 2002) are directlyassociated with nonsyndromic ID. Two of these mutations, the gly218-to-ter nonsense mutation and the 2-bp deletion predict a truncatedprotein lacking the fourth transmembrane domain and cytoplasmic

C. Verpelli et al. / European Journal of Pharmacology 719 (2013) 112–116 115

C-terminal tail. Thus not surprisingly the function of TSPAN7 in brain iscorrelated to synapse development and plasticity.

It has been recently showed that TSPAN7 promotes filopodiaand dendritic spine formation in cultured hippocampal neurons,and is required for spine stability and normal synaptic transmis-sion. The C-terminal tail of TSPAN7 binds also to PICK1 (proteininteracting with C kinase 1), a protein involved in the internaliza-tion and recycling of AMPA receptors (Perez et al., 2001). IndeedTSPAN7 is a synaptic proteins that regulates the association ofPICK1 with AMPARs, and controls AMPAR trafficking. These datarecognize TSPAN7 as a key molecule in the morphological andfunctional maturation of glutamatergic synapses, and indicates amolecular mechanisms that links TM4SF2 gene mutations to ID(Bassani et al., 2012).

4. Conclusions and prospectives

The discovery of molecular mechanisms contributing to thepathogenesis of diverse types of genetically determined ID andASD offers new possible targets for the discovery of drugs to atleast ameliorate these neurological pathologies.

For example because the SHANK and TM4SF2 mutations seems tolead to a hypoglutamatergic state, the up regulation of the gluta-matergic systemmay be a possible therapeutic approach. The use ofAMPAkines, agents that activate synaptic currents mediated byAMPA-type glutamate receptors, are indeed a possible pharmaco-logical approach (Hamdan et al., 2011).These drugs improve theinduction of long-term potentiation and exert a positive effect onexcitatory transmission also by inducing the synthesis of factors likethe brain-derived neurotrophic factor (BDNF) which is involved insynaptic plasticity and memory consolidation (Jourdi et al., 2009).

Our data suggest that allosteric modulators of mGlu5 – like theCDPPB – are able to rescue in vitro synaptic defects of Shank3knockdown neurons (Verpelli et al., 2011). CDPPB was also used torescue behavioral defects in the Tsc2 and Shank2 knock out mice(Auerbach et al., 2011; Won et al., 2012). On the contrary, mGlu5inhibitors are efficiently used to rescue neurological defects in fmrpknock out mice, the animal model for the Fragile X syndrome. Thesedrugs are actually used in clinical trials in patients with the Fragile Xsyndrome (Levenga et al., 2010). Interestingly these data suggestthat an optimal range of metabotropic glutamate-receptor-mediatedsignalling is required for normal synaptic plasticity and cognitivefunctions, and both positive and negative alterations of this pathwaymight direct to similar ID impairments. Thus a possible importantchallenge for the pharmacological research will be to identifymolecules and treatments able to finely modulate glutamatergictransmission in order to normalize the altered synapse function andameliorate the cognitive function of ID patients.

Aknowledgmets

FundingThis work was supported by Grants Telethon – Italy (Grant no.

GGP11095), Fondazione CARIPLO, Italian Institute of Technology,Seed Grant and Ministry of Health in the frame of ERA-NETNEURON. C.H. is supported by Marie Curie Actions 71 FrameworkProgramme: SyMBad Marie Curie (Synapse: from molecules tobrain diseases) International Research and Training program2002–2007.

References

Abidi, F.E., Holinski-Feder, E., Rittinger, O., Kooy, F., Lubs, H.A., Stevenson, R.E.,Schwartz, C.E., 2002. A novel 2bp deletion in the TM4SF2 gene is associatedwith MRX58. J. Med. Genet. 39, 430–433.

Auerbach, B.D., Osterweil, E.K., Bear, M.F., 2011. Mutations causing syndromicautism define an axis of synaptic pathophysiology. Nature 480, 63–68.

Bahi, N., Friocourt, G., Carrie, A., Graham, M.E., Weiss, J.L., Chafey, P., Fauchereau, F.,Burgoyne, R.D., Chelly, J., 2003. IL1 receptor accessory protein like, a proteininvolved in X-linked mental retardation, interacts with neuronal calciumsensor-1 and regulates exocytosis. Hum. Mol. Genet. 12, 1415–1425.

Bassani, S., Cingolani, L.A., Valnegri, P., Folci, A., Zapata, J., Gianfelice, A., Sala, C.,Goda, Y., Passafaro, M., 2012. The X-linked intellectual disability protein TSPAN7regulates excitatory synapse development and AMPAR trafficking. Neuron 73,1143–1158.

Berditchevski, F., 2001. Complexes of tetraspanins with integrins: more than meetsthe eye. J. Cell Sci. 114, 4143–4151.

Berkel, S., Marshall, C.R., Weiss, B., Howe, J., Roeth, R., Moog, U., Endris, V., Roberts,W., Szatmari, P., Pinto, D., Bonin, M., Riess, A., Engels, H., Sprengel, R., Scherer, S.W., Rappold, G.A., 2010. Mutations in the SHANK2 synaptic scaffolding gene inautism spectrum disorder and mental retardation. Nat. Genet. 42, 489–491.

Bhat, S.S., Ladd, S., Grass, F., Spence, J.E., Brasington, C.K., Simensen, R.J., Schwartz, C.E.,Dupont, B.R., Stevenson, R.E., Srivastava, A.K., 2008. Disruption of the IL1RAPL1 geneassociated with a pericentromeric inversion of the X chromosome in a patient withmental retardation and autism. Clin. Genet. 73, 94–96.

Blanpied, T.A., Ehlers, M.D., 2004. Microanatomy of dendritic spines: emergingprinciples of synaptic pathology in psychiatric and neurological disease. Biol.Psychiatry 55, 1121–1127.

Bockers, T.M., Segger-Junius, M., Iglauer, P., Bockmann, J., Gundelfinger, E.D., Kreutz,M.R., Richter, D., Kindler, S., Kreienkamp, H.J., 2004. Differential expression anddendritic transcript localization of Shank family members: identification of adendritic targeting element in the 3' untranslated region of Shank1 mRNA. Mol.Cell Neurosci. 26, 182–190.

Boda, B., Mas, C., Muller, D., 2002. Activity-dependent regulation of genes implicated inX-linked non-specific mental retardation. Neuroscience 114, 13–17.

Bonaglia, M.C., Giorda, R., Borgatti, R., Felisari, G., Gagliardi, C., Selicorni, A., Zuffardi, O.,2001. Disruption of the ProSAP2 gene in a t(12;22)(q24.1;q13.3) is associated withthe 22q13.3 deletion syndrome. Am. J. Hum. Genet. 69, 261–268.

Boucheix, C., Rubinstein, E., 2001. Tetraspanins. Cell Mol. Life Sci. 58, 1189–1205.Bozdagi, O., Sakurai, T., Papapetrou, D., Wang, X., Dickstein, D.L., Takahashi, N.,

Kajiwara, Y., Yang, M., Katz, A.M., Scattoni, M.L., Harris, M.J., Saxena, R.,Silverman, J.L., Crawley, J.N., Zhou, Q., Hof, P.R., Buxbaum, J.D., 2010. Haploin-sufficiency of the autism-associated Shank3 gene leads to deficits in synapticfunction, social interaction, and social communication. Mol. Autism 1, 15.

Carrie, A., Jun, L., Bienvenu, T., Vinet, M.C., McDonell, N., Couvert, P., Zemni, R.,Cardona, A., Van Buggenhout, G., Frints, S., Hamel, B., Moraine, C., Ropers, H.H.,Strom, T., Howell, G.R., Whittaker, A., Ross, M.T., Kahn, A., Fryns, J.P., Beldjord, C.,Marynen, P., Chelly, J., 1999. A new member of the IL-1 receptor family highlyexpressed in hippocampus and involved in X-linked mental retardation. Nat.Genet. 23, 25–31.

Chavis, P., Westbrook, G., 2001. Integrins mediate functional pre- and postsynapticmaturation at a hippocampal synapse. Nature 411, 317–321.

Chen, B.S., Thomas, E.V., Sanz-Clemente, A., Roche, K.W., 2011. NMDA receptor-dependent regulation of dendritic spine morphology by SAP102 splice variants.J. Neurosci. 31, 89–96.

Cheng, M.C., Lu, C.L., Luu, S.U., Tsai, H.M., Hsu, S.H., Chen, T.T., Chen, C.H., 2010.Genetic and functional analysis of the DLG4 gene encoding the post-synapticdensity protein 95 in schizophrenia. PLoS One 5, e15107.

Delahaye, A., Toutain, A., Aboura, A., Dupont, C., Tabet, A.C., Benzacken, B., Elion, J.,Verloes, A., Pipiras, E., Drunat, S., 2009. Chromosome 22q13.3 deletionsyndrome with a de novo interstitial 22q13.3 cryptic deletion disruptingSHANK3. Eur. J. Med. Genet. 52, 328–332.

Durand, C.M., Betancur, C., Boeckers, T.M., Bockmann, J., Chaste, P., Fauchereau, F.,Nygren, G., Rastam, M., Gillberg, I.C., Anckarsater, H., Sponheim, E., Goubran-Botros, H., Delorme, R., Chabane, N., Mouren-Simeoni, M.C., de Mas, P., Bieth, E.,Roge, B., Heron, D., Burglen, L., Gillberg, C., Leboyer, M., Bourgeron, T., 2007.Mutations in the gene encoding the synaptic scaffolding protein SHANK3 areassociated with autism spectrum disorders. Nat. Genet. 39, 25–27.

Feyder, M., Karlsson, R.M., Mathur, P., Lyman, M., Bock, R., Momenan, R., Munasinghe, J.,Scattoni, M.L., Ihne, J., Camp, M., Graybeal, C., Strathdee, D., Begg, A., Alvarez, V.A.,Kirsch, P., Rietschel, M., Cichon, S., Walter, H., Meyer-Lindenberg, A., Grant, S.G.,Holmes, A., 2010. Association of mouse Dlg4 (PSD-95) gene deletion and humanDLG4 gene variation with phenotypes relevant to autism spectrum disorders andWilliams' syndrome. Am. J. Psychiatry 167, 1508–1517.

Franek, K.J., Butler, J., Johnson, J., Simensen, R., Friez, M.J., Bartel, F., Moss, T., DuPont,B., Berry, K., Bauman, M., Skinner, C., Stevenson, R.E., Schwartz, C.E., 2011.Deletion of the immunoglobulin domain of IL1RAPL1 results in nonsyndromicX-linked intellectual disability associated with behavioral problems and milddysmorphism. Am. J. Med. Genet. A 155A, 1109–1114.

Gambino, F., Pavlowsky, A., Béglé, A., Dupont, J.L., Bahi, N., Courjaret, R., Gardette, R.,Hadjkacem, H., Skala, H., Poulain, B., Chelly, J., Vitale, N., Humeau, Y., 2007. IL1-receptor accessory protein-like 1 (IL1RAPL1), a protein involved in cognitivefunctions, regulates N-type Ca2+-channel and neurite elongation. Proc. Natl.Acad. Sci. U. S. A. 104, 9063–9068.

Gauthier, J., Spiegelman, D., Piton, A., Lafreniere, R.G., Laurent, S., St-Onge, J.,Lapointe, L., Hamdan, F.F., Cossette, P., Mottron, L., Fombonne, E., Joober, R.,Marineau, C., Drapeau, P., Rouleau, G.A., 2009. Novel de novo SHANK3 mutationin autistic patients. Am. J. Med. Genet. B Neuropsychiatr. Genet. 150B, 421–424.

Govek, E.E., Newey, S.E., Akerman, C.J., Cross, J.R., Van der Veken, L., Van Aelst, L.,2004. The X-linked mental retardation protein oligophrenin-1 is required fordendritic spine morphogenesis. Nat. Neurosci. 7, 364–372.

C. Verpelli et al. / European Journal of Pharmacology 719 (2013) 112–116116

Hamdan, F.F., Gauthier, J., Araki, Y., Lin, D.T., Yoshizawa, Y., Higashi, K., Park, A.R.,Spiegelman, D., Dobrzeniecka, S., Piton, A., Tomitori, H., Daoud, H., Massicotte, C.,Henrion, E., Diallo, O., Shekarabi, M., Marineau, C., Shevell, M., Maranda, B.,Mitchell, G., Nadeau, A., D'Anjou, G., Vanasse, M., Srour, M., Lafrenière, R.G.,Drapeau, P., Lacaille, J.C., Kim, E., Lee, J.R., Igarashi, K., Huganir, R.L., Rouleau, G.A.,Michaud, J.L., Group, S.D., 2011. Excess of de novo deleterious mutations in genesassociated with glutamatergic systems in nonsyndromic intellectual disability. Am.J. Hum. Genet. 88, 306–316.

Hemler, M.E., 1998. Integrin associated proteins. Curr. Opin. Cell Biol. 10, 578–585.Hemler, M.E., 2005. Tetraspanin functions and associated microdomains. Nat. Rev.

Mol. Cell Biol. 6, 801–811.Hemler, M.E., 2008. Targeting of tetraspanin proteins—potential benefits and

strategies. Nat. Rev. Drug Discov. 7, 747–758.Hung, A.Y., Futai, K., Sala, C., Valtschanoff, J.G., Ryu, J., Woodworth, M.A., Kidd, F.L.,

Sung, C.C., Miyakawa, T., Bear, M.F., Weinberg, R.J., Sheng, M., 2008. Smallerdendritic spines, weaker synaptic transmission, but enhanced spatial learningin mice lacking Shank1. J. Neurosci. 28, 1697–1708.

Jamain, S., Quach, H., Betancur, C., Rastam, M., Colineaux, C., Gillberg, I.C.,Soderstrom, H., Giros, B., Leboyer, M., Gillberg, C., Bourgeron, T., 2003. Muta-tions of the X-linked genes encoding neuroligins NLGN3 and NLGN4 areassociated with autism. Nat. Genet. 34, 27–29.

Jourdi, H., Hsu, Y.T., Zhou, M., Qin, Q., Bi, X., Baudry, M., 2009. Positive AMPAreceptor modulation rapidly stimulates BDNF release and increases dendriticmRNA translation. J. Neurosci. 29, 8688–8697.

Khelfaoui, M., Denis, C., van Galen, E., de Bock, F., Schmitt, A., Houbron, C., Morice, E.,Giros, B., Ramakers, G., Fagni, L., Chelly, J., Nosten-Bertrand, M., Billuart, P., 2007. Lossof X-linked mental retardation gene oligophrenin1 in mice impairs spatial memoryand leads to ventricular enlargement and dendritic spine immaturity. J. Neurosci. 27,9439–9450.

Khelfaoui, M., Pavlowsky, A., Powell, A.D., Valnegri, P., Cheong, K.W., Blandin, Y.,Passafaro, M., Jefferys, J.G., Chelly, J., Billuart, P., 2009. Inhibition of RhoApathway rescues the endocytosis defects in Oligophrenin1 mouse model ofmental retardation. Hum. Mol. Genet. 18, 2575–2583.

Laumonnier, F., Cuthbert, P.C., Grant, S.G., 2007. The role of neuronal complexes inhuman X-linked brain diseases. Am. J. Hum. Genet. 80, 205–220.

Levenga, J., de Vrij, F.M., Oostra, B.A., Willemsen, R., 2010. Potential therapeuticinterventions for fragile X syndrome. Trends Mol. Med. 16, 516–527.

Manning, M.A., Cassidy, S.B., Clericuzio, C., Cherry, A.M., Schwartz, S., Hudgins, L.,Enns, G.M., Hoyme, H.E., 2004. Terminal 22q deletion syndrome: a newlyrecognized cause of speech and language disability in the autism spectrum.Pediatrics 114, 451–457.

Moessner, R., Marshall, C.R., Sutcliffe, J.S., Skaug, J., Pinto, D., Vincent, J., Zwaigenbaum, L.,Fernandez, B., Roberts, W., Szatmari, P., Scherer, S.W., 2007. Contribution of SHANK3mutations to autism spectrum disorder. Am. J. Hum. Genet. 81, 1289–1297.

Nadif Kasri, N., Nakano-Kobayashi, A., Malinow, R., Li, B., Van Aelst, L., 2009. TheRho-linked mental retardation protein oligophrenin-1 controls synapse matura-tion and plasticity by stabilizing AMPA receptors. Genes Dev. 23, 1289–1302.

Nadif Kasri, N., Van Aelst, L., 2008. Rho-linked genes and neurological disorders.Pflugers Arch. 455, 787–797.

Pavlowsky, A., Gianfelice, A., Pallotto, M., Zanchi, A., Vara, H., Khelfaoui, M., Valnegri, P.,Rezai, X., Bassani, S., Brambilla, D., Kumpost, J., Blahos, J., Roux, M.J., Humeau, Y.,Chelly, J., Passafaro, M., Giustetto, M., Billuart, P., Sala, C., 2010. A postsynapticsignaling pathway that may account for the cognitive defect due to IL1RAPL1mutation. Curr. Biol. 20, 103–115.

Perez, J.L., Khatri, L., Chang, C., Srivastava, S., Osten, P., Ziff, E.B., 2001. PICK1 targetsactivated protein kinase calpha to AMPA receptor clusters in spines ofhippocampal neurons and reduces surface levels of the AMPA-type glutamatereceptor subunit 2. J. Neurosci. 21, 5417–5428.

Peça, J., Feliciano, C., Ting, J.T., Wang, W., Wells, M.F., Venkatraman, T.N., Lascola, C.D.,Fu, Z., Feng, G., 2011. Shank3 mutant mice display autistic-like behaviours andstriatal dysfunction. Nature.

Phelan, M.C., Rogers, R.C., Saul, R.A., Stapleton, G.A., Sweet, K., McDermid, H., Shaw,S.R., Claytor, J., Willis, J., Kelly, D.P., 2001. 22q13 deletion syndrome. Am. J. Med.Genet. 101, 91–99.

Piton, A., Michaud, J.L., Peng, H., Aradhya, S., Gauthier, J., Mottron, L., Champagne, N.,Lafrenière, R.G., Hamdan, F.F., Joober, R., Fombonne, E., Marineau, C., Cossette, P.,Dubé, M.P., Haghighi, P., Drapeau, P., Barker, P.A., Carbonetto, S., Rouleau, G.A., team,S.D., 2008. Mutations in the calcium-related gene IL1RAPL1 are associated withautism. Hum. Mol. Genet. 17, 3965–3974.

Powell, A.D., Gill, K.K., Saintot, P.P., Jiruska, P., Chelly, J., Billuart, P., Jefferys, J.G.,2012. Rapid reversal of impaired inhibitory and excitatory transmission but notspine dysgenesis in a mouse model of mental retardation. J. Physiol. 590,763–776.

Rauch, A., Hoyer, J., Guth, S., Zweier, C., Kraus, C., Becker, C., Zenker, M., Hüffmeier, U.,Thiel, C., Rüschendorf, F., Nürnberg, P., Reis, A., Trautmann, U., 2006. Diagnosticyield of various genetic approaches in patients with unexplained developmentaldelay or mental retardation. Am. J. Med. Genet. A 140, 2063–2074.

Ropers, H.H., Hamel, B.C., 2005. X-linked mental retardation. Nat. Rev. Genet. 6,46–57.

Sato, D., Lionel, A.C., Leblond, C.S., Prasad, A., Pinto, D., Walker, S., O'Connor, I., Russell, C.,Drmic, I.E., Hamdan, F.F., Michaud, J.L., Endris, V., Roeth, R., Delorme, R., Huguet, G.,Leboyer, M., Rastam, M., Gillberg, C., Lathrop, M., Stavropoulos, D.J., Anagnostou, E.,Weksberg, R., Fombonne, E., Zwaigenbaum, L., Fernandez, B.A., Roberts, W., Rappold,G.A., Marshall, C.R., Bourgeron, T., Szatmari, P., Scherer, S.W., 2012. SHANK1 deletionsin males with autism spectrum disorder. Am. J. Hum. Genet. 90, 879–887.

Schmeisser, M.J., Ey, E., Wegener, S., Bockmann, J., Stempel, A.V., Kuebler, A.,Janssen, A.L., Udvardi, P.T., Shiban, E., Spilker, C., Balschun, D., Skryabin, B.V.,Dieck, S., Smalla, K.H., Montag, D., Leblond, C.S., Faure, P., Torquet, N., Le Sourd,A.M., Toro, R., Grabrucker, A.M., Shoichet, S.A., Schmitz, D., Kreutz, M.R.,Bourgeron, T., Gundelfinger, E.D., Boeckers, T.M., 2012. Autistic-like behavioursand hyperactivity in mice lacking ProSAP1/Shank2. Nature 486, 256–260.

Südhof, T.C., 2008. Neuroligins and neurexins link synaptic function to cognitivedisease. Nature 455, 903–911.

Tarpey, P., Parnau, J., Blow, M., Woffendin, H., Bignell, G., Cox, C., Cox, J., Davies, H.,Edkins, S., Holden, S., Korny, A., Mallya, U., Moon, J., O'Meara, S., Parker, A.,Stephens, P., Stevens, C., Teague, J., Donnelly, A., Mangelsdorf, M., Mulley, J.,Partington, M., Turner, G., Stevenson, R., Schwartz, C., Young, I., Easton, D.,Bobrow, M., Futreal, P.A., Stratton, M.R., Gecz, J., Wooster, R., Raymond, F.L.,2004. Mutations in the DLG3 gene cause nonsyndromic X-linked mentalretardation. Am. J. Hum. Genet. 75, 318–324.

Valnegri, P., Khelfaoui, M., Dorseuil, O., Bassani, S., Lagneaux, C., Gianfelice, A.,Benfante, R., Chelly, J., Billuart, P., Sala, C., Passafaro, M., 2011a. A circadian clockin hippocampus is regulated by interaction between oligophrenin-1 and Rev-erbα. Nat. Neurosci.

Valnegri, P., Montrasio, C., Brambilla, D., Ko, J.W., Passafaro, M., Sala, C., 2011b. TheX-linked intellectual disability protein IL1RAPL1 regulates excitatory synapseformation by binding PTPδ and RhoGAP2.

Verpelli, C., Dvoretskova, E., Vicidomini, C., Rossi, F., Chiappalone, M., Schoen, M., DiStefano, B., Mantegazza, R., Broccoli, V., Boeckers, T.M., Dityatev, A., Sala, C.,2011. Importance of shank3 in regulating metabotropic glutamate receptor 5(mGluR5) expression and signaling at synapses. J. Biol. Chem.

Wang, X., McCoy, P.A., Rodriguiz, R.M., Pan, Y., Je, H.S., Roberts, A.C., Kim, C.J.,Berrios, J., Colvin, J.S., Bousquet-Moore, D., Lorenzo, I., Wu, G., Weinberg, R.J.,Ehlers, M.D., Philpot, B.D., Beaudet, A.L., Wetsel, W.C., Jiang, Y.H., 2011. Synapticdysfunction and abnormal behaviors in mice lacking major isoforms of Shank3.Hum. Mol. Genet.

Wilson, H.L., Wong, A.C., Shaw, S.R., Tse, W.Y., Stapleton, G.A., Phelan, M.C., Hu, S.,Marshall, J., McDermid, H.E., 2003. Molecular characterisation of the 22q13deletion syndrome supports the role of haploinsufficiency of SHANK3/PROSAP2in the major neurological symptoms. J. Med. Genet. 40, 575–584.

Won, H., Lee, H.R., Gee, H.Y., Mah, W., Kim, J.I., Lee, J., Ha, S., Chung, C., Jung, E.S.,Cho, Y.S., Park, S.G., Lee, J.S., Lee, K., Kim, D., Bae, Y.C., Kaang, B.K., Lee, M.G.,Kim, E., 2012. Autistic-like social behavior in Shank2-mutant mice improved byrestoring NMDA receptor function. Nature 486, 261–265.

Wöhr, M., Roullet, F.I., Hung, A.Y., Sheng, M., Crawley, J.N., 2011. Communicationimpairments in mice lacking Shank1: reduced levels of ultrasonic vocalizationsand scent marking behavior. PLoS One 6, e20631.

Yauch, R.L., Kazarov, A.R., Desai, B., Lee, R.T., Hemler, M.E., 2000. Direct extracellularcontact between integrin alpha(3)beta(1) and TM4SF protein CD151. J. Biol.Chem. 275, 9230–9238.

Yoshida, T., Yasumura, M., Uemura, T., Lee, S.J., Ra, M., Taguchi, R., Iwakura, Y.,Mishina, M., 2011. IL-1 Receptor Accessory Protein-Like 1 Associated withMental Retardation and Autism Mediates Synapse Formation by Trans-SynapticInteraction with Protein Tyrosine Phosphatase {delta}. J. Neurosci. 31,13485–13499.

Zanni, G., van Esch, H., Bensalem, A., Saillour, Y., Poirier, K., Castelnau, L., Ropers, H.H., de Brouwer, A.P., Laumonnier, F., Fryns, J.P., Chelly, J., 2010. A novel mutationin the DLG3 gene encoding the synapse-associated protein 102 (SAP102) causesnon-syndromic mental retardation. Neurogenetics 11, 251–255.

Zemni, R., Bienvenu, T., Vinet, M.C., Sefiani, A., Carrié, A., Billuart, P., McDonell, N.,Couvert, P., Francis, F., Chafey, P., Fauchereau, F., Friocourt, G., des Portes, V., Cardona,A., Frints, S., Meindl, A., Brandau, O., Ronce, N., Moraine, C., van Bokhoven, H., Ropers,H.H., Sudbrak, R., Kahn, A., Fryns, J.P., Beldjord, C., Chelly, J., 2000. A new geneinvolved in X-linked mental retardation identified by analysis of an X;2 balancedtranslocation. Nat. Genet. 24, 167–170.