Autism spectrum disorder (ASD) is a group of conditions characterized by impaired social interaction and communication, and restricted and repetitive behaviours. ASD is a highly heritable disorder ...involving various genetic determinants. Shank2 (also known as ProSAP1) is a multi-domain scaffolding protein and signalling adaptor enriched at excitatory neuronal synapses, and mutations in the human SHANK2 gene have recently been associated with ASD and intellectual disability. Although ASD-associated genes are being increasingly identified and studied using various approaches, including mouse genetics, further efforts are required to delineate important causal mechanisms with the potential for therapeutic application. Here we show that Shank2-mutant (Shank2(-/-)) mice carrying a mutation identical to the ASD-associated microdeletion in the human SHANK2 gene exhibit ASD-like behaviours including reduced social interaction, reduced social communication by ultrasonic vocalizations, and repetitive jumping. These mice show a marked decrease in NMDA (N-methyl-D-aspartate) glutamate receptor (NMDAR) function. Direct stimulation of NMDARs with D-cycloserine, a partial agonist of NMDARs, normalizes NMDAR function and improves social interaction in Shank2(-/-) mice. Furthermore, treatment of Shank2(-/-) mice with a positive allosteric modulator of metabotropic glutamate receptor 5 (mGluR5), which enhances NMDAR function via mGluR5 activation, also normalizes NMDAR function and markedly enhances social interaction. These results suggest that reduced NMDAR function may contribute to the development of ASD-like phenotypes in Shank2(-/-) mice, and mGluR modulation of NMDARs offers a potential strategy to treat ASD.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
NMDA receptor (NMDAR) and GABA neuronal dysfunctions are observed in animal models of autism spectrum disorders, but how these dysfunctions impair social cognition and behavior remains ...unclear. We report here that NMDARs in cortical parvalbumin (Pv)-positive interneurons cooperate with gap junctions to promote high-frequency (>80 Hz) Pv neuronal burst firing and social cognition.
Shank2
–/–
mice, displaying improved sociability upon NMDAR activation, show impaired cortical social representation and inhibitory neuronal burst firing. Cortical
Shank2
–/–
Pv neurons show decreased NMDAR activity, which suppresses the cooperation between NMDARs and gap junctions (GJs) for normal burst firing.
Shank2
–/–
Pv neurons show compensatory increases in GJ activity that are not sufficient for social rescue. However, optogenetic boosting of Pv neuronal bursts, requiring GJs, rescues cortical social cognition in
Shank2
–/–
mice, similar to the NMDAR-dependent social rescue. Therefore, NMDARs and gap junctions cooperate to promote cortical Pv neuronal bursts and social cognition.
Autism spectrum disorders (ASDs) are four times more common in males than in females, but the underlying mechanisms are poorly understood. We characterized sexually dimorphic changes in mice carrying ...a heterozygous mutation in Chd8 (Chd8
) that was first identified in human CHD8 (Asn2373LysfsX2), a strong ASD-risk gene that encodes a chromatin remodeler. Notably, although male mutant mice displayed a range of abnormal behaviors during pup, juvenile, and adult stages, including enhanced mother-seeking ultrasonic vocalization, enhanced attachment to reunited mothers, and isolation-induced self-grooming, their female counterparts do not. This behavioral divergence was associated with sexually dimorphic changes in neuronal activity, synaptic transmission, and transcriptomic profiles. Specifically, female mice displayed suppressed baseline neuronal excitation, enhanced inhibitory synaptic transmission and neuronal firing, and increased expression of genes associated with extracellular vesicles and the extracellular matrix. Our results suggest that a human CHD8 mutation leads to sexually dimorphic changes ranging from transcription to behavior in mice.
Shank2 is a multidomain scaffolding protein implicated in the structural and functional coordination of multiprotein complexes at excitatory postsynaptic sites as well as in psychiatric disorders, ...including autism spectrum disorders. While Shank2 is strongly expressed in the cerebellum, whether Shank2 regulates cerebellar excitatory synapses, or contributes to the behavioral abnormalities observed in Shank2
mice, remains unexplored. Here we show that Shank2
mice show reduced excitatory synapse density in cerebellar Purkinje cells in association with reduced levels of excitatory postsynaptic proteins, including GluD2 and PSD-93, and impaired motor coordination in the Erasmus test. Shank2 deletion restricted to Purkinje cells (Pcp2-Cre;Shank2
mice) leads to similar reductions in excitatory synapse density, synaptic protein levels, and motor coordination. Pcp2-Cre;Shank2
mice do not recapitulate autistic-like behaviors observed in Shank2
mice, such as social interaction deficits, altered ultrasonic vocalizations, repetitive behaviors, and hyperactivity. However, Pcp2-Cre;Shank2
mice display enhanced repetitive behavior in the hole-board test and anxiety-like behavior in the light-dark test, which are not observed in Shank2
mice. These results implicate Shank2 in the regulation of cerebellar excitatory synapse density, motor coordination, and specific repetitive and anxiety-like behaviors.
The postsynaptic side of excitatory synapses contains multiprotein complexes, termed the postsynaptic density, which contains receptors, scaffolding/adaptor proteins, and signaling molecules. Shank2 is an excitatory postsynaptic scaffolding protein implicated in the formation and functional coordination of the postsynaptic density and has been linked to autism spectrum disorders. Using Shank2-null mice and Shank2-conditional knock-out mice with a gene deletion restricted to cerebellar Purkinje cells, we explored functions of Shank2 in the cerebellum. We found that Shank2 regulates excitatory synapse density, motor coordination, and specific repetitive and anxiety-like behaviors, but is not associated with autistic-like social deficits or repetitive behaviors.
Genetic aspects of autism spectrum disorders (ASDs) have recently been extensively explored, but environmental influences that affect ASDs have received considerably less attention. Zinc (Zn) is a ...nutritional factor implicated in ASDs, but evidence for a strong association and linking mechanism is largely lacking. Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation.
Autism spectrum disorder involves neurodevelopmental dysregulations that lead to visible symptoms at early stages of life. Many autism spectrum disorder–related mechanisms suggested by animal studies ...are supported by demonstrated improvement in autistic-like phenotypes in adult animals following experimental reversal of dysregulated mechanisms. However, whether such mechanisms also act at earlier stages to cause autistic-like phenotypes is unclear.
We used Shank2−/− mice carrying a mutation identified in human autism spectrum disorder (exons 6 and 7 deletion) and combined electrophysiological and behavioral analyses to see whether early pathophysiology at pup stages is different from late pathophysiology at juvenile and adult stages and whether correcting early pathophysiology can normalize late pathophysiology and abnormal behaviors in juvenile and adult mice.
Early correction of a dysregulated mechanism in young mice prevents manifestation of autistic-like social behaviors in adult mice. Shank2−/− mice, known to display N-methyl-D-aspartate receptor (NMDAR) hypofunction and autistic-like behaviors at postweaning stages after postnatal day 21 (P21), show the opposite synaptic phenotype—NMDAR hyperfunction—at an earlier preweaning stage (∼P14). Moreover, this NMDAR hyperfunction at P14 rapidly shifts to NMDAR hypofunction after weaning (∼P24). Chronic suppression of the early NMDAR hyperfunction by the NMDAR antagonist memantine (P7–P21) prevents NMDAR hypofunction and autistic-like social behaviors from manifesting at later stages (∼P28 and P56).
Early NMDAR hyperfunction leads to late NMDAR hypofunction and autistic-like social behaviors in Shank2−/− mice, and early correction of NMDAR dysfunction has the long-lasting effect of preventing autistic-like social behaviors from developing at later stages.
SALM1 (SALM (synaptic adhesion-like molecule), also known as LRFN2 (leucine rich repeat and fibronectin type III domain containing), is a postsynaptic density (PSD)-95-interacting synaptic adhesion ...molecule implicated in the regulation of NMDA receptor (NMDAR) clustering largely based on
data, although its
functions remain unclear. Here, we found that mice lacking SALM1/LRFN2 (
mice) show a normal density of excitatory synapses but altered excitatory synaptic function, including enhanced NMDAR-dependent synaptic transmission but suppressed NMDAR-dependent synaptic plasticity in the hippocampal CA1 region. Unexpectedly, SALM1 expression was detected in both glutamatergic and GABAergic neurons and
CA1 pyramidal neurons showed decreases in the density of inhibitory synapses and the frequency of spontaneous inhibitory synaptic transmission. Behaviorally, ultrasonic vocalization was suppressed in
pups separated from their mothers and acoustic startle was enhanced, but locomotion, anxiety-like behavior, social interaction, repetitive behaviors, and learning and memory were largely normal in adult male
mice. These results suggest that SALM1/LRFN2 regulates excitatory synapse function, inhibitory synapse development, and social communication and startle behaviors in mice.
Synaptic adhesion molecules regulate synapse development and function, which govern neural circuit and brain functions. The SALM/LRFN (synaptic adhesion-like molecule/leucine rich repeat and fibronectin type III domain containing) family of synaptic adhesion proteins consists of five known members for which the
functions are largely unknown. Here, we characterized mice lacking SALM1/LRFN2 (SALM1 KO) known to associate with NMDA receptors (NMDARs) and found that these mice showed altered NMDAR-dependent synaptic transmission and plasticity, as expected, but unexpectedly also exhibited suppressed inhibitory synapse development and synaptic transmission. Behaviorally, SALM1 KO pups showed suppressed ultrasonic vocalization upon separation from their mothers and SALM1 KO adults showed enhanced responses to loud acoustic stimuli. These results suggest that SALM1/LRFN2 regulates excitatory synapse function, inhibitory synapse development, social communication, and acoustic startle behavior.
Shank2 is an excitatory postsynaptic scaffolding protein strongly implicated in autism spectrum disorders (ASDs).
Shank2
-mutant mice with a homozygous deletion of exons 6 and 7 (
Shank2
-KO mice) ...show decreased NMDA receptor (NMDAR) function and autistic-like behaviors at juvenile ∼postnatal day (P21) and adult (>P56) stages that are rescued by NMDAR activation. However, at ∼P14, these mice show the opposite change – increased NMDAR function; moreover, suppression of NMDAR activity with early, chronic memantine treatment during P7–21 prevents NMDAR hypofunction and autistic-like behaviors at later (∼P21 and >P56) stages. To better understand the mechanisms underlying this rescue, we performed RNA-Seq gene-set enrichment analysis of forebrain transcriptomes from wild-type (WT) and
Shank2
-KO juvenile (P25) mice treated early and chronically (P7–21) with vehicle or memantine. Vehicle-treated
Shank2
-KO mice showed upregulation of synapse-related genes and downregulation of ribosome- and mitochondria-related genes compared with vehicle-treated WT mice. They also showed a transcriptomic pattern largely opposite that observed in ASD (reverse-ASD pattern), based on ASD-related/risk genes and cell-type–specific genes. In memantine-treated
Shank2
-KO mice, chromatin-related genes were upregulated; mitochondria, extracellular matrix (ECM), and actin-related genes were downregulated; and the reverse-ASD pattern was weakened compared with that in vehicle-treated
Shank2
-KO mice. In WT mice, memantine treatment, which does not alter NMDAR function, upregulated synaptic genes and downregulated ECM genes; memantine-treated WT mice also exhibited a reverse-ASD pattern. Therefore, early chronic treatment of
Shank2
-KO mice with memantine alters expression of chromatin, mitochondria, ECM, actin, and ASD-related genes.
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social and repetitive symptoms. A key feature of ASD is early-life manifestations of symptoms, indicative of early ...pathophysiological mechanisms. In mouse models of ASD, increasing evidence indicates that there are early pathophysiological mechanisms that can be corrected early to prevent phenotypic defects in adults, overcoming the disadvantage of the short-lasting effects that characterize adult-initiated treatments. In addition, the results from gene restorations indicate that ASD-related phenotypes can be rescued in some cases even after the brain has fully matured. These results suggest that we need to consider both temporal and mechanistic aspects in studies of ASD models and carefully compare genetic and nongenetic corrections. Here, we summarize the early and late corrections in mouse models of ASD by genetic and pharmacological interventions and discuss how to better integrate these results to ensure efficient and long-lasting corrections for eventual clinical translation.
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