Activation of the medial preoptic area (MPOA) ameliorates loss of maternal behavior in a Shank2 mouse model for autism.

Impairments in social relationships and awareness are features observed in autism spectrum disorders (ASDs). However, the underlying mechanisms remain poorly understood. Shank2 is a high-confidence ASD candidate gene and localizes primarily to postsynaptic densities (PSDs) of excitatory synapses in the central nervous system (CNS). We show here that loss of Shank2 in mice leads to a lack of social attachment and bonding behavior towards pubs independent of hormonal, cognitive, or sensitive deficits. Shank2-/- mice display functional changes in nuclei of the social attachment circuit that were most prominent in the medial preoptic area (MPOA) of the hypothalamus. Selective enhancement of MPOA activity by DREADD technology re-established social bonding behavior in Shank2-/- mice, providing evidence that the identified circuit might be crucial for explaining how social deficits in ASD can arise.

The postsynaptic density proteins Homer and Shank form a polymeric network structure.

The postsynaptic density (PSD) is crucial for synaptic functions, but the molecular architecture retaining its structure and components remains elusive. Homer and Shank are among the most abundant scaffolding proteins in the PSD, working synergistically for maturation of dendritic spines. Here, we demonstrate that Homer and Shank, together, form a mesh-like matrix structure. Crystallographic analysis of this region revealed a pair of parallel dimeric coiled coils intercalated in a tail-to-tail fashion to form a tetramer, giving rise to the unique configuration of a pair of N-terminal EVH1 domains at each end of the coiled coil. In neurons, the tetramerization is required for structural integrity of the dendritic spines and recruitment of proteins to synapses. We propose that the Homer-Shank complex serves as a structural framework and as an assembly platform for other PSD proteins.

Shank2/3 double knockout-based screening of cortical subregions links the retrosplenial area to the loss of social memory in autism spectrum disorders.

Members of the Shank protein family are master scaffolds of the postsynaptic architecture and mutations within the SHANK genes are causally associated with autism spectrum disorders (ASDs). We generated a Shank2-Shank3 double knockout mouse that is showing severe autism related core symptoms, as well as a broad spectrum of comorbidities. We exploited this animal model to identify cortical brain areas linked to specific autistic traits by locally deleting Shank2 and Shank3 simultaneously. Our screening of 10 cortical subregions revealed that a Shank2/3 deletion within the retrosplenial area severely impairs social memory, a core symptom of ASD. Notably, DREADD-mediated neuronal activation could rescue the social impairment triggered by Shank2/3 depletion. Data indicate that the retrosplenial area has to be added to the list of defined brain regions that contribute to the spectrum of behavioural alterations seen in ASDs.

The development of ADAM10 endocytosis inhibitors for the treatment of Alzheimer's disease.

The development of new therapeutic avenues that target the early stages of Alzheimer's disease (AD) is urgently necessary. A disintegrin and metalloproteinase domain 10 (ADAM10) is a sheddase that is involved in dendritic spine shaping and limits the generation of amyloid-ß. ADAM10 endocytosis increases in the hippocampus of AD patients, resulting in the decreased postsynaptic localization of the enzyme. To restore this altered pathway, we developed a cell-permeable peptide (PEP3) with a strong safety profile that is able to interfere with ADAM10 endocytosis, upregulating the postsynaptic localization and activity of ADAM10. After extensive validation, experiments in a relevant animal model clarified the optimal timing of the treatment window. PEP3 administration was effective for the rescue of cognitive defects in APP/PS1 mice only if administered at an early disease stage. Increased ADAM10 activity promoted synaptic plasticity, as revealed by changes in the molecular compositions of synapses and the spine morphology. Even though further studies are required to evaluate efficacy and safety issues of long-term administration of PEP3, these results provide preclinical evidence to support the therapeutic potential of PEP3 in AD.

Developmental impaired Akt signaling in the Shank1 and Shank3 double knock-out mice.

Human mutations and haploinsufficiency of the SHANK family genes are associated with autism spectrum disorders (ASD) and intellectual disability (ID). Complex phenotypes have been also described in all mouse models of Shank mutations and deletions, consistent with the heterogeneity of the human phenotypes. However, the specific role of Shank proteins in synapse and neuronal functions remain to be elucidated. Here, we generated a new mouse model to investigate how simultaneously deletion of Shank1 and Shank3 affects brain development and behavior in mice. Shank1-Shank3 DKO mice showed a low survival rate, a developmental strong reduction in the activation of intracellular signaling pathways involving Akt, S6, ERK1/2, and eEF2 during development and a severe behavioral impairments. Our study suggests that Shank1 and Shank3 proteins are essential to developmentally regulate the activation of Akt and correlated intracellular pathways crucial for mammalian postnatal brain development and synaptic plasticity. Therefore, Akt function might represent a new therapeutic target for enhancing cognitive abilities of syndromic ASD patients.

Restoring glutamate receptosome dynamics at synapses rescues autism-like deficits in Shank3-deficient mice.

Shank3 monogenic mutations lead to autism spectrum disorders (ASD). Shank3 is part of the glutamate receptosome that physically links ionotropic NMDA receptors to metabotropic mGlu5 receptors through interactions with scaffolding proteins PSD95-GKAP-Shank3-Homer. A main physiological function of the glutamate receptosome is to control NMDA synaptic function that is required for plasticity induction. Intact glutamate receptosome supports glutamate receptors activation and plasticity induction, while glutamate receptosome disruption blocks receptors activity, preventing the induction of subsequent plasticity. Despite possible impact on metaplasticity and cognitive behaviors, scaffold interaction dynamics and their consequences are poorly defined. Here, we used mGlu5-Homer interaction as a biosensor of glutamate receptosome integrity to report changes in synapse availability for plasticity induction. Combining BRET imaging and electrophysiology, we show that a transient neuronal depolarization inducing NMDA-dependent plasticity disrupts glutamate receptosome in a long-lasting manner at synapses and activates signaling pathways required for the expression of the initiated neuronal plasticity, such as ERK and mTOR pathways. Glutamate receptosome disruption also decreases the NMDA/AMPA ratio, freezing the sensitivity of the synapse to subsequent changes of neuronal activity. These data show the importance of a fine-tuning of protein-protein interactions within glutamate receptosome, driven by changes of neuronal activity, to control plasticity. In a mouse model of ASD, a truncated mutant form of Shank3 prevents the integrity of the glutamate receptosome. These mice display altered plasticity, anxiety-like, and stereotyped behaviors. Interestingly, repairing the integrity of glutamate receptosome and its sensitivity to the neuronal activity rescued synaptic transmission, plasticity, and some behavioral traits of Shank3∆C mice. Altogether, our findings characterize mechanisms by which Shank3 mutations cause ASD and highlight scaffold dynamics as new therapeutic target.

SULT4A1 Modulates Synaptic Development and Function by Promoting the Formation of PSD-95/NMDAR Complex.

Sulfotransferase 4A1 (SULT4A1) is a cytosolic sulfotransferase that is highly conserved across species and extensively expressed in the brain. However, the biological function of SULT4A1 is unclear. SULT4A1 has been implicated in several neuropsychiatric disorders, such as Phelan-McDermid syndrome and schizophrenia. Here, we investigate the role of SULT4A1 within neuron development and function. Our data demonstrate that SULT4A1 modulates neuronal branching complexity and dendritic spines formation. Moreover, we show that SULT4A1, by negatively regulating the catalytic activity of Pin1 toward PSD-95, facilitates NMDAR synaptic expression and function. Finally, we demonstrate that the pharmacological inhibition of Pin1 reverses the pathologic phenotypes of neurons knocked down by SULT4A1 by specifically restoring dendritic spine density and rescuing NMDAR-mediated synaptic transmission. Together, these findings identify SULT4A1 as a novel player in neuron development and function by modulating dendritic morphology and synaptic activity.SIGNIFICANCE STATEMENT Sulfotransferase 4A1 (SULT4A1) is a brain-specific sulfotransferase highly expressed in neurons. Different evidence has suggested that SULT4A1 has an important role in neuronal function and that SULT4A1 altered expression might represent a contributing factor in multiple neurodevelopmental disorders. However, the function of SULT4A1 in the mammalian brain is still unclear. Here, we demonstrate that SULT4A1 is highly expressed at postsynaptic sites where it sequesters Pin1, preventing its negative action on synaptic transmission. This study reveals a novel role of SULT4A1 in the modulation of NMDA receptor activity and strongly contributes to explaining the neuronal dysfunction observed in patients carrying deletions of SULTA41 gene.

Another step toward understanding brain functional connectivity alterations in autism: An Editorial Highlight for "Neurobiological substrates underlying corpus callosum hypoconnectivity and brain metabolic patterns in the valproic acid rat model of autism spectrum disorder" on page 128.

Various neuroimaging approaches have reported alterations in brain connectivity in patients with autism spectrum disorder (ASD). Nevertheless, specific cellular and molecular mechanisms underlying these alterations remain to be elucidated. In the present Editorial, we highlight an article in the current issue of the Journal of Neurochemistry that provides first evidence for the structural and cellular basis of an atypical corpus callosum long-distance connectivity impairments observed in ASD patients. The authors used a juvenile valproic acid (VPA) rat model of ASD that presents with reduced myelin level, specifically in the corpus callosum, and with an altered myelin sheet structure that is closely associated with the behavioral alteration found in these rats. This hypomyelination occurs primarily during infancy prior to oligodendroglial alterations, implicating that axonal-oligodendroglial connections are compromised in this model. Concomitant with the hypomyelination, the ASD rat model showed an atypical brain metabolic pattern, with hypometabolic activity across the whole brain, and hypermetabolism in brain areas related to autistic-like behavior. These findings contribute to unravel the neurobiological basis underlying white matter alteration and altered long-distance brain connectivity as described in ASD, paving the way to the development of new early diagnostic markers and toward developing future specific therapies for ASD.

AIMTOR, a BRET biosensor for live imaging, reveals subcellular mTOR signaling and dysfunctions.

BACKGROUND: mTOR signaling is an essential nutrient and energetic sensing pathway. Here we describe AIMTOR, a sensitive genetically encoded BRET (Bioluminescent Resonance Energy Transfer) biosensor to study mTOR activity in living cells. RESULTS: As a proof of principle, we show in both cell lines and primary cell cultures that AIMTOR BRET intensities are modified by mTOR activity changes induced by specific inhibitors and activators of mTORC1 including amino acids and insulin. We further engineered several versions of AIMTOR enabling subcellular-specific assessment of mTOR activities. We then used AIMTOR to decipher mTOR signaling in physio-pathological conditions. First, we show that mTORC1 activity increases during muscle cell differentiation and in response to leucine stimulation in different subcellular compartments such as the cytosol and at the surface of the lysosome, the nucleus, and near the mitochondria. Second, in hippocampal neurons, we found that the enhancement of neuronal activity increases mTOR signaling. AIMTOR further reveals mTOR-signaling dysfunctions in neurons from mouse models of autism spectrum disorder. CONCLUSIONS: Altogether, our results demonstrate that AIMTOR is a sensitive and specific tool to investigate mTOR-signaling dynamics in living cells and phenotype mTORopathies.

The X-Linked Intellectual Disability Protein IL1RAPL1 Regulates Dendrite Complexity.

Mutations and deletions of the interleukin-1 receptor accessory protein like 1 (IL1RAPL1) gene, located on the X chromosome, are associated with intellectual disability (ID) and autism spectrum disorder (ASD). IL1RAPL1 protein is located at the postsynaptic compartment of excitatory synapses and plays a role in synapse formation and stabilization. Here, using primary neuronal cultures and Il1rapl1-KO mice, we characterized the role of IL1RAPL1 in regulating dendrite morphology. In Il1rapl1-KO mice we identified an increased number of dendrite branching points in CA1 and CA2 hippocampal neurons associated to hippocampal cognitive impairment. Similarly, induced pluripotent stem cell-derived neurons from a patient carrying a null mutation of the IL1RAPL1 gene had more dendrites. In hippocampal neurons, the overexpression of full-length IL1RAPL1 and mutants lacking part of C-terminal domains leads to simplified neuronal arborization. This effect is abolished when we overexpressed mutants lacking part of N-terminal domains, indicating that the IL1RAPL1 extracellular domain is required for regulating dendrite development. We also demonstrate that PTPδ interaction is not required for this activity, while IL1RAPL1 mediates the activity of IL-1ß on dendrite morphology. Our data reveal a novel specific function for IL1RAPL1 in regulating dendrite morphology that can help clarify how changes in IL1RAPL1-regulated pathways can lead to cognitive disorders in humans.SIGNIFICANCE STATEMENT Abnormalities in the architecture of dendrites have been observed in a variety of neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Here we show that the X-linked intellectual disability protein interleukin-1 receptor accessory protein like 1 (IL1RAPL1) regulates dendrite morphology of mice hippocampal neurons and induced pluripotent stem cell-derived neurons from a patient carrying a null mutation of IL1RAPL1 gene. We also found that the extracellular domain of IL1RAPL1 is required for this effect, independently of the interaction with PTPδ, but IL1RAPL1 mediates the activity of IL-1ß on dendrite morphology. Our data reveal a novel specific function for IL1RAPL1 in regulating dendrite morphology that can help clarify how changes in IL1RAPL1-regulated pathways can lead to cognitive disorders in humans.

eEF2K/eEF2 Pathway Controls the Excitation/Inhibition Balance and Susceptibility to Epileptic Seizures.

Alterations in the balance of inhibitory and excitatory synaptic transmission have been implicated in the pathogenesis of neurological disorders such as epilepsy. Eukaryotic elongation factor 2 kinase (eEF2K) is a highly regulated, ubiquitous kinase involved in the control of protein translation. Here, we show that eEF2K activity negatively regulates GABAergic synaptic transmission. Indeed, loss of eEF2K increases GABAergic synaptic transmission by upregulating the presynaptic protein Synapsin 2b and α5-containing GABAA receptors and thus interferes with the excitation/inhibition balance. This cellular phenotype is accompanied by an increased resistance to epilepsy and an impairment of only a specific hippocampal-dependent fear conditioning. From a clinical perspective, our results identify eEF2K as a potential novel target for antiepileptic drugs, since pharmacological and genetic inhibition of eEF2K can revert the epileptic phenotype in a mouse model of human epilepsy.

Modelling Autistic Neurons with Induced Pluripotent Stem Cells.

Autism spectrum disorder (ASD) is a neurodevelopmental condition that affects more than 1% of children per current estimates. It has been characterised by the following two core behavioural phenotypes: (1) deficits in social interaction and communication and (2) repetitive behaviours, restricted interests and activities. Due to the complex nature of ASD, there are currently no effective treatments. The reason behind this is the clinical and genetic heterogeneity between affected individuals on the one hand and the lack of understanding of the underpinning pathophysiological mechanisms on the other hand. Induced pluripotent stem cells (iPSCs) are reprogrammed stem cells from adult cells. These have the capacity to self-renew and differentiate into any type of cells in the body. Therefore, human iPSCs provide a unique opportunity to study the human cellular and molecular phenotypes associated with ASD. Here, we systematically review various ASD variants and co-morbid diseases modelled using human iPSCs.

Shank synaptic scaffold proteins: keys to understanding the pathogenesis of autism and other synaptic disorders.

Shank/ProSAP proteins are essential to synaptic formation, development, and function. Mutations in the family of SHANK genes are strongly associated with autism spectrum disorders (ASD) and other neurodevelopmental and neuropsychiatric disorders, such as intellectual disability (ID), and schizophrenia. Thus, the term 'Shankopathies' identifies a number of neuronal diseases caused by alteration of Shank protein expression leading to abnormal synaptic development. With this review we want to summarize the major genetic, molecular, behavior and electrophysiological studies that provide new clues into the function of Shanks and pave the way for the discovery of new therapeutic drugs targeted to treat patients with SHANK mutations and also patients affected by other neurodevelopmental and neuropsychiatric disorders. Shank/ProSAP proteins are essential to synaptic formation, development, and function. Mutations in the family of SHANK genes are strongly associated with autism spectrum disorders (ASD) and other neurodevelopmental and neuropsychiatric disorders, such as intellectual disability (ID), and schizophrenia (SCZ). With this review we want to summarize the major genetic, molecular, behavior and electrophysiological studies that provide new clues into the function of Shanks and pave the way for the discovery of new therapeutic drugs targeted to treat patients with SHANK mutations.

SHANK3 gene mutations associated with autism facilitate ligand binding to the Shank3 ankyrin repeat region.

Shank/ProSAP proteins are major scaffold proteins of the postsynaptic density; mutations in the human SHANK3 gene are associated with intellectual disability or autism spectrum disorders. We have analyzed the functional relevance of several SHANK3 missense mutations affecting the N-terminal portion of the protein by expression of wild-type and mutant Shank3 in cultured neurons and by binding assays in heterologous cells. Postsynaptic targeting of recombinant Shank3 was unaltered. In electrophysiological experiments, both wild-type and L68P mutant forms of Shank3 were equally effective in restoring synaptic function after knockdown of endogenous Shank3. We observed that several mutations affected binding to interaction partners of the Shank3 ankyrin repeat region. One of these mutations, L68P, improved binding to both ligands. Leu-68 is located N-terminal to the ankyrin repeats, in a highly conserved region that we identify here as a novel domain termed the Shank/ProSAP N-terminal (SPN) domain. We show that the SPN domain interacts with the ankyrin repeats in an intramolecular manner, thereby restricting access of either Sharpin or α-fodrin. The L68P mutation disrupts this blockade, thus exposing the Shank3 ankyrin repeat region to its ligands. Our data identify a new type of regulation of Shank proteins and suggest that mutations in the SHANK3 gene do not necessarily induce a loss of function, but may represent a gain of function with respect to specific interaction partners.

Phosphorylation of neuronal Lysine-Specific Demethylase 1LSD1/KDM1A impairs transcriptional repression by regulating interaction with CoREST and histone deacetylases HDAC1/2.

Epigenetic mechanisms play important roles in brain development, orchestrating proliferation, differentiation, and morphogenesis. Lysine-Specific Demethylase 1 (LSD1 also known as KDM1A and AOF2) is a histone modifier involved in transcriptional repression, forming a stable core complex with the corepressors corepressor of REST (CoREST) and histone deacetylases (HDAC1/2). Importantly, in the mammalian CNS, neuronal LSD1-8a, an alternative splicing isoform of LSD1 including the mini-exon E8a, sets alongside LSD1 and is capable of enhancing neurite growth and morphogenesis. Here, we describe that the morphogenic properties of neuronal LSD1-8a require switching off repressive activity and this negative modulation is mediated in vivo by phosphorylation of the Thr369b residue coded by exon E8a. Three-dimensional crystal structure analysis using a phospho-mimetic mutant (Thr369bAsp), indicate that phosphorylation affects the residues surrounding the exon E8a-coded amino acids, causing a local conformational change. We suggest that phosphorylation, without affecting demethylase activity, causes in neurons CoREST and HDAC1/2 corepressors detachment from LSD1-8a and impairs neuronal LSD1-8a repressive activity. In neurons, Thr369b phosphorylation is required for morphogenic activity, converting neuronal LSD1-8a in a dominant-negative isoform, challenging LSD1-mediated transcriptional repression on target genes.

The neuropeptide PACAP38 induces dendritic spine remodeling through ADAM10-N-cadherin signaling pathway.

The neuropeptide pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) has been implicated in the induction of synaptic plasticity at the excitatory glutamatergic synapse. In particular, recent studies have shown that it is involved in the regulation of N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor activation. Here we demonstrate the effect of PACAP38 on the modulation of dendritic spine morphology through a disintegrin and metalloproteinase 10 (ADAM10)-N-cadherin-AMPA receptor signaling pathway. Treatment of primary hippocampal neurons with PACAP38 induced an accumulation of ADAM10 at the postsynaptic membrane. This event led to a significant decrease of dendritic spine head width and to a concomitant reduction of GluR1 colocalization with postsynaptic markers. The PACAP38-induced effect on dendritic spine head width was prevented by either treatment with the ADAM10-specific inhibitor or transfection of a cleavage-defective N-cadherin construct mutated in the ADAM10 cleavage site. Overall, our findings reveal that PACAP38 is involved in the modulation of dendritic spine morphology in hippocampal neurons, and assign to the ADAM10-N-cadherin signaling pathway a crucial role in this modification of the excitatory glutamatergic synapse.

Shank3 deletion in PV neurons is associated with abnormal behaviors and neuronal functions that are rescued by increasing GABAergic signaling.

BACKGROUND: Phelan-McDermid syndrome (PMS) is a neurodevelopmental disorder characterized by developmental delay, intellectual disability, and autistic-like behaviors and is primarily caused by haploinsufficiency of SHANK3 gene. Currently, there is no specific treatment for PMS, highlighting the need for a better understanding of SHANK3 functions and the underlying pathophysiological mechanisms in the brain. We hypothesize that SHANK3 haploinsufficiency may lead to alterations in the inhibitory system, which could be linked to the excitatory/inhibitory imbalance observed in models of autism spectrum disorder (ASD). Investigation of these neuropathological features may shed light on the pathogenesis of PMS and potential therapeutic interventions. METHODS: We recorded local field potentials and visual evoked responses in the visual cortex of Shank3∆11-/- mice. Then, to understand the impact of Shank3 in inhibitory neurons, we generated Pv-cre+/- Shank3Fl/Wt conditional mice, in which Shank3 was deleted in parvalbumin-positive neurons. We characterized the phenotype of this murine model and we compared this phenotype before and after ganaxolone administration. RESULTS: We found, in the primary visual cortex, an alteration of the gain control of Shank3 KO compared with Wt mice, indicating a deficit of inhibition on pyramidal neurons. This alteration was rescued after the potentiation of GABAA receptor activity by Midazolam. Behavioral analysis showed an impairment in grooming, memory, and motor coordination of Pv-cre+/- Shank3Fl/Wt compared with Pv-cre+/- Shank3Wt/Wt mice. These deficits were rescued with ganaxolone, a positive modulator of GABAA receptors. Furthermore, we demonstrated that treatment with ganaxolone also ameliorated evocative memory deficits and repetitive behavior of Shank3 KO mice. LIMITATIONS: Despite the significant findings of our study, some limitations remain. Firstly, the neurobiological mechanisms underlying the link between Shank3 deletion in PV neurons and behavioral alterations need further investigation. Additionally, the impact of Shank3 on other classes of inhibitory neurons requires further exploration. Finally, the pharmacological activity of ganaxolone needs further characterization to improve our understanding of its potential therapeutic effects. CONCLUSIONS: Our study provides evidence that Shank3 deletion leads to an alteration in inhibitory feedback on cortical pyramidal neurons, resulting in cortical hyperexcitability and ASD-like behavioral problems. Specifically, cell type-specific deletion of Shank3 in PV neurons was associated with these behavioral deficits. Our findings suggest that ganaxolone may be a potential pharmacological approach for treating PMS, as it was able to rescue the behavioral deficits in Shank3 KO mice. Overall, our study highlights the importance of investigating the role of inhibitory neurons and potential therapeutic interventions in neurodevelopmental disorders such as PMS.

Definition and clinical variability of SHANK3-related Phelan-McDermid syndrome.

Phelan-McDermid syndrome (PMS) is an infrequently described syndrome that presents with a disturbed development, neurological and psychiatric characteristics, and sometimes other comorbidities. As part of the development of European medical guidelines we studied the definition, phenotype, genotype-phenotype characteristics, and natural history of the syndrome. The number of confirmed diagnoses of PMS in different European countries was also assessed and it could be concluded that PMS is underdiagnosed. The incidence of PMS in European countries is estimated to be at least 1 in 30,000. Next generation sequencing, including analysis of copy number variations, as first tier in diagnostics of individuals with intellectual disability will likely yield a larger number of individuals with PMS than presently known. A definition of PMS by its phenotype is at the present not possible, and therefore PMS-SHANK3 related is defined by the presence of SHANK3 haploinsufficiency, either by a deletion involving region 22q13.2-33 or a pathogenic/likely pathogenic variant in SHANK3. In summarizing the phenotype, we subdivided it into that of individuals with a 22q13 deletion and that of those with a pathogenic/likely pathogenic SHANK3 variant. The phenotype of individuals with PMS is variable, depending in part on the deletion size or whether only a variant of SHANK3 is present. The core phenotype in the domains development, neurology, and senses are similar in those with deletions and SHANK3 variants, but individuals with a SHANK3 variant more often are reported to have behavioural disorders and less often urogenital malformations and lymphedema. The behavioural disorders may, however, be a less outstanding feature in individuals with deletions accompanied by more severe intellectual disability. Data available on the natural history are limited. Results of clinical trials using IGF-1, intranasal insulin, and oxytocin are available, other trials are in progress. The present guidelines for PMS aim at offering tools to caregivers and families to provide optimal care to individuals with PMS.

Shank2 identifies a subset of glycinergic neurons involved in altered nociception in an autism model.

BACKGROUND: Autism Spectrum Disorders (ASD) patients experience disturbed nociception in the form of either hyposensitivity to pain or allodynia. A substantial amount of processing of somatosensory and nociceptive stimulus takes place in the dorsal spinal cord. However, many of these circuits are not very well understood in the context of nociceptive processing in ASD. METHODS: We have used a Shank2-/- mouse model, which displays a set of phenotypes reminiscent of ASD, and performed behavioural and microscopic analysis to investigate the role of dorsal horn circuitry in nociceptive processing of ASD. RESULTS: We determined that Shank2-/- mice display increased sensitivity to formalin pain and thermal preference, but a sensory specific mechanical allodynia. We demonstrate that high levels of Shank2 expression identifies a subpopulation of neurons in murine and human dorsal spinal cord, composed mainly by glycinergic interneurons and that loss of Shank2 causes the decrease in NMDAR in excitatory synapses on these inhibitory interneurons. In fact, in the subacute phase of the formalin test, glycinergic interneurons are strongly activated in wild type (WT) mice but not in Shank2-/- mice. Consequently, nociception projection neurons in laminae I are activated in larger numbers in Shank2-/- mice. LIMITATIONS: Our investigation is limited to male mice, in agreement with the higher representation of ASD in males; therefore, caution should be applied to extrapolate the findings to females. Furthermore, ASD is characterized by extensive genetic diversity and therefore the findings related to Shank2 mutant mice may not necessarily apply to patients with different gene mutations. Since nociceptive phenotypes in ASD range between hyper- and hypo-sensitivity, diverse mutations may affect the circuit in opposite ways. CONCLUSION: Our findings prove that Shank2 expression identifies a new subset of inhibitory interneurons involved in reducing the transmission of nociceptive stimuli and whose unchecked activation is associated with pain hypersensitivity. We provide evidence that dysfunction in spinal cord pain processing may contribute to the nociceptive phenotypes in ASD.

Importance of Shank3 protein in regulating metabotropic glutamate receptor 5 (mGluR5) expression and signaling at synapses.

Shank3/PROSAP2 gene mutations are associated with cognitive impairment ranging from mental retardation to autism. Shank3 is a large scaffold postsynaptic density protein implicated in dendritic spines and synapse formation; however, its specific functions have not been clearly demonstrated. We have used RNAi to knockdown Shank3 expression in neuronal cultures and showed that this treatment specifically reduced the synaptic expression of the metabotropic glutamate receptor 5 (mGluR5), but did not affect the expression of other major synaptic proteins. The functional consequence of Shank3 RNAi knockdown was impaired signaling via mGluR5, as shown by reduction in ERK1/2 and CREB phosphorylation induced by stimulation with (S)-3,5-dihydroxyphenylglycine (DHPG) as the agonist of mGluR5 receptors, impaired mGluR5-dependent synaptic plasticity (DHPG-induced long-term depression), and impaired mGluR5-dependent modulation of neural network activity. We also found morphological abnormalities in the structure of synapses (spine number, width, and length) and impaired glutamatergic synaptic transmission, as shown by reduction in the frequency of miniature excitatory postsynaptic currents (mEPSC). Notably, pharmacological augmentation of mGluR5 activity using 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)-benzamide as the positive allosteric modulator of these receptors restored mGluR5-dependent signaling (DHPG-induced phosphorylation of ERK1/2) and normalized the frequency of mEPSCs in Shank3-knocked down neurons. These data demonstrate that a deficit in mGluR5-mediated intracellular signaling in Shank3 knockdown neurons can be compensated by 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)-benzamide; this raises the possibility that pharmacological augmentation of mGluR5 activity represents a possible new therapeutic approach for patients with Shank3 mutations.