Gene_locus Report for: mouse-3neur

Multiple candidate genes have been identified for autism spectrum disorders. While some of these genes reach genome-wide significance, others, such as the R451C point mutation in the synaptic cell adhesion molecule neuroligin-3, appear to be rare. Interestingly, two brothers with the same R451C point mutation in neuroligin-3 present clinically on seemingly disparate sides of the autism spectrum. These clinical findings suggest genetic background may play a role in modifying the penetrance of a particular autism-associated mutation. Animal models may contribute additional support for such mutations as functionally relevant and can provide mechanistic insights. Previously, in collaboration with the Sudhof laboratory, we reported that mice with an R451C substitution in neuroligin-3 displayed social deficits and enhanced spatial learning. While some of these behavioral abnormalities have since been replicated independently in the Sudhof laboratory, observations from the Crawley laboratory failed to replicate these findings in a similar neuroligin-3 mutant mouse model and suggested that genetic background may contribute to variation in observations across laboratories. Therefore, we sought to replicate our findings in the neuroligin-3 R451C point mutant knock-in mouse model (NL3R451C) in a different genetic background. We backcrossed our NL3R451C mouse line onto a 129S2/SvPasCrl genetic background and repeated a subset of our previous behavioral testing. NL3R451C mice on a 129S2/SvPasCrl displayed social deficits, enhanced spatial learning, and increased locomotor activity. These data extend our previous findings that NL3R451C mice exhibit autism-relevant behavioral abnormalities and further suggest that different genetic backgrounds can modify this behavioral phenotype through epistatic genetic interactions. Autism Res 2014, 7: 264-272. (c) 2014 International Society for Autism Research, Wiley Periodicals, Inc.

Only a small proportion of the mouse genome is transcribed into mature messenger RNA transcripts. There is an international collaborative effort to identify all full-length mRNA transcripts from the mouse, and to ensure that each is represented in a physical collection of clones. Here we report the manual annotation of 60,770 full-length mouse complementary DNA sequences. These are clustered into 33,409 'transcriptional units', contributing 90.1% of a newly established mouse transcriptome database. Of these transcriptional units, 4,258 are new protein-coding and 11,665 are new non-coding messages, indicating that non-coding RNA is a major component of the transcriptome. 41% of all transcriptional units showed evidence of alternative splicing. In protein-coding transcripts, 79% of splice variations altered the protein product. Whole-transcriptome analyses resulted in the identification of 2,431 sense-antisense pairs. The present work, completely supported by physical clones, provides the most comprehensive survey of a mammalian transcriptome so far, and is a valuable resource for functional genomics.

The molecular mechanisms that drive glia-glial interactions and glia-neuronal interactions during the development of the nervous system are poorly understood. A number of membrane-bound cell adhesion molecules have been shown to play a role, although the precise nature of their involvement is unknown. One class of molecules with cell adhesive properties used in the nervous system is the serine-esterase-like family of transmembrane proteins. A member of this class, a glia-specific protein called gliotactin, has been shown to be necessary for the development of the glial sheath in the peripheral nervous system of Drosophila melanogaster. Gliotactin is essential for the development of septate junctions in the glial sheath of individual and neighboring glia. Mutations that remove this protein result in paralysis and eventually death due to a breakdown in the glial-based blood-nerve barrier. To study the role of gliotactin during vertebrate nervous system development, we have isolated a potential vertebrate gliotactin homologue from mice and rat and found that it corresponds to neuroligin 3. Using a combination of RT-PCR and immunohistochemistry, we have found that neuroligin 3 is expressed during the development of the nervous system in many classes of glia. In particular neuroligin 3 is expressed in the olfactory ensheathing glia, retinal astrocytes, Schwann cells, and spinal cord astrocytes in the developing embryo. This expression is developmentally controlled such that in postnatal and adult stages, neuroligin 3 continues to be expressed at high levels in the olfactory ensheathing glia, a highly plastic class of glia that retain many of their developmental characteristics throughout life.

Gastrointestinal (GI) problems constitute an important comorbidity in many patients with autism. Multiple mutations in the neuroligin family of synaptic adhesion molecules are implicated in autism, however whether they are expressed and impact GI function via changes in the enteric nervous system is unknown. We report the GI symptoms of two brothers with autism and an R451C mutation in Nlgn3 encoding the synaptic adhesion protein, neuroligin-3. We confirm the presence of an array of synaptic genes in the murine GI tract and investigate the impact of impaired synaptic protein expression in mice carrying the human neuroligin-3 R451C missense mutation (NL3(R451C) ). Assessing in vivo gut dysfunction, we report faster small intestinal transit in NL3(R451C) compared to wild-type mice. Using an ex vivo colonic motility assay, we show increased sensitivity to GABAA receptor modulation in NL3(R451C) mice, a well-established Central Nervous System (CNS) feature associated with this mutation. We further show increased numbers of small intestine myenteric neurons in NL3(R451C) mice. Although we observed altered sensitivity to GABAA receptor modulators in the colon, there was no change in colonic neuronal numbers including the number of GABA-immunoreactive myenteric neurons. We further identified altered fecal microbial communities in NL3(R451C) mice. These results suggest that the R451C mutation affects small intestinal and colonic function and alter neuronal numbers in the small intestine as well as impact fecal microbes. Our findings identify a novel GI phenotype associated with the R451C mutation and highlight NL3(R451C) mice as a useful preclinical model of GI dysfunction in autism. Autism Res 2019, 12: 1043-1056. (c) 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: People with autism commonly experience gastrointestinal problems, however the cause is unknown. We report gut symptoms in patients with the autism-associated R451C mutation encoding the neuroligin-3 protein. We show that many of the genes implicated in autism are expressed in mouse gut. The neuroligin-3 R451C mutation alters the enteric nervous system, causes gastrointestinal dysfunction, and disrupts gut microbe populations in mice. Gut dysfunction in autism could be due to mutations that affect neuronal communication.

Cognitive dysfunction including disrupted behavioral flexibility is central to neurodevelopmental disorders such as Autism Spectrum Disorder (ASD). A cognitive measure that assesses relational memory, and the ability to flexibly assimilate and transfer learned information is transitive inference. Transitive inference is highly conserved across vertebrates and disrupted in cognitive disorders. Here, we examined how mutations in the synaptic cell-adhesion molecule neuroligin-3 (Nlgn3) that have been documented in ASD impact relational memory and behavioral flexibility. We first refined a rodent touchscreen assay to measure visual transitive inference, then assessed two mouse models of Nlgn3 dysfunction (Nlgn3 (-/y) and Nlgn3 (R451C)). Deep analysis of touchscreen behavioral data at a trial level established we could measure trajectories in flexible responding and changes in processing speed as cognitive load increased. We show that gene mutations in Nlgn3 do not disrupt relational memory, but significantly impact flexible responding. Our study presents the first analysis of reaction times in a rodent transitive inference test, highlighting response latencies from the touchscreen system are useful indicators of processing demands or decision-making processes. These findings expand our understanding of how dysfunction of key components of synaptic signaling complexes impact distinct cognitive processes disrupted in neurodevelopmental disorders, and advance our approaches for dissecting rodent behavioral assays to provide greater insights into clinically relevant cognitive symptoms.

Neuroligins (NLs) are critical for synapse formation and function. NL3 R451C is an autism-associated mutation. NL3 R451C knockin (KI) mice exhibit autistic behavioral abnormalities, including social novelty deficits. However, neither the brain regions involved in social novelty nor the underlying mechanisms are clearly understood. Here, we found decreased excitability of fast-spiking interneurons and dysfunction of gamma oscillation in the medial prefrontal cortex (mPFC), which contributed to the social novelty deficit in the KI mice. Neuronal firing rates and phase-coding abnormalities were also detected in the KI mice during social interactions. Interestingly, optogenetic stimulation of parvalbumin interneurons in the mPFC at 40 Hz nested at 8 Hz positively modulated the social behaviors of mice and rescued the social novelty deficit in the KI mice. Our findings suggest that gamma oscillation dysfunction in the mPFC leads to social deficits in autism, and manipulating mPFC PV interneurons may reverse the deficits in adulthood.

Understanding neuronal mechanisms underlying aggression in patients with autism spectrum disorder (ASD) could lead to better treatments and prognosis. The Neuroligin-3 (NL3)(R451C) mouse model of ASD has a heightened aggressive phenotype, however the biological mechanisms underlying this behavior are unknown. It is well established that NL3(R451C) mice have imbalanced excitatory and inhibitory synaptic activity in the hippocampus and somatosensory cortex. The amygdala plays a role in modulating aggressive behavior, however potential changes in synaptic activity in this region have not previously been assessed in this model. We investigated whether aggressive behavior is robustly present in mice expressing the R451C mutation, following back-crossing onto a congenic background strain. Endocannabinoids influence social interaction and aggressive behavior, therefore we also studied the effects of cannabinoid receptor 1 (CB1) agonist on NL3(R451C) mice. We report that NL3(R451C) mice have increased amplitude of miniature excitatory postsynaptic currents (EPSCs) with a concomitant decrease in the amplitude of inhibitory postsynaptic currents (IPSCs) in the basolateral amygdala. Importantly, we demonstrated that NL3(R451C) mice bred on a C57Bl/6 background strain exhibit an aggressive phenotype. Following non-sedating doses (0.3 and 1.0 mg/kg) of the CB1 receptor agonist WIN55,212-2 (WIN), we observed a significant reduction in aggressive behavior in NL3(R451C) mice. These findings demonstrate altered synaptic activity in the basolateral amygdala and suggest that the NL3(R451C) mouse model is a useful preclinical tool to understand the role of CB1 receptor function in aggressive behavior.

Neuroligin-3 (NLGN3) is a postsynaptic cell adhesion protein that interacts with presynaptic ligands including neurexin-1 (NRXN1) [Ichtchenko et al., Journal of Biological Chemistry, 271, 2676-2682, 1996]. Mice harboring a mutation in the NLGN3 gene (NL3R451C) mimicking a mutation found in two brothers with autism spectrum disorder (ASD) were previously generated and behaviorally phenotyped for autism-related behaviors. In these NL3R451C mice generated and tested on a hybrid C57BL6J/129S2/SvPasCrl background, we observed enhanced spatial memory and reduced social interaction [Tabuchi et al., Science, 318, 71-76, 2007]. Curiously, an independently generated second line of mice harboring the same mutation on a C57BL6J background exhibited minimal aberrant behavior, thereby providing apparently discrepant results. To investigate the origin of the discrepancy, we previously replicated the original findings of Tabuchi et al. by studying the same NL3R451C mutation on a pure 129S2/SvPasCrl genetic background. Here we complete the behavioral characterization of the NL3R451C mutation on a pure C57BL6J genetic background to determine if background genetics play a role in the discrepant behavioral outcomes involving NL3R451C mice. NL3R451C mutant mice on a pure C57BL6J background did not display spatial memory enhancements or social interaction deficits. We only observed a decreased startle response and mildly increased locomotor activity in these mice suggesting that background genetics influences behavioral outcomes involving the NL3R451C mutation. LAY SUMMARY: Behavioral symptoms of autism can be highly variable, even in cases that involve identical genetic mutations. Previous studies in mice with a mutation of the Neuroligin-3 gene showed enhanced learning and social deficits. We replicated these findings on the same and different genetic backgrounds. In this study, however, the same mutation in mice on a different genetic background did not reproduce our previous findings. Our results suggest that genetic background influences behavioral symptoms of this autism-associated mutation.

Autism spectrum disorders (ASDs) comprise a heterogeneous group of disorders with a complex genetic etiology. Current theories on the pathogenesis of ASDs suggest that they might arise from an aberrant synaptic transmission affecting specific brain circuits and synapses. The striatum, which is part of the basal ganglia circuit, is one of the brain regions involved in ASDs. Mouse models of ASDs have provided evidence for an imbalance between excitatory and inhibitory neurotransmission. Here, we investigated the expression of long-term synaptic plasticity at corticostriatal glutamatergic synapses in the dorsal striatum of the R451C-NL3 phenotypic mouse model of autism. This mouse model carries the human R451C mutation in the neuroligin 3 (NL3) gene that has been associated with highly penetrant autism in a Swedish family. The R451C-NL3 mouse has been shown to exhibit autistic-like behaviors and alterations of synaptic transmission in different brain areas. However, excitatory glutamatergic transmission and its long-term plasticity have not been investigated in the dorsal striatum so far. Our results indicate that the expression of long-term synaptic depression (LTD) at corticostriatal glutamatergic synapses in the dorsal striatum is impaired by the R451C-NL3 mutation. A partial rescue of LTD was obtained by exogenous activation of cannabinoid CB1 receptors or enhancement of the endocannabinoid tone, suggesting that an altered cannabinoid drive might underlie the deficit of synaptic plasticity in the dorsal striatum of R451C-NL3 mice.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder typified by impaired social communication and restrictive and repetitive behaviors. Mice serve as an ideal candidate organism for studying the neural mechanisms that subserve these symptoms. The Neuroligin-3 (NL3) mouse, expressing a R451C mutation discovered in two Swedish brothers with ASD, exhibits impaired social interactions and heightened aggressive behavior towards male mice. Social interactions with female mice have not been characterized and in the present study were assessed in male NL3R451C and WT mice. Mice were housed in social and isolation conditions to test for isolation-induced increases in social interaction. Tests were repeated to investigate potential differences in interaction in naive and experienced mice. We identified heightened interest in mating and atypical aggressive behavior in NL3R451C mice. NL3R451C mice exhibited normal social interaction with WT females, indicating that abnormal aggressive behavior towards females is not due to altered motivation to engage. Social isolation rearing heightened interest in social behavior in all mice. Isolation housing selectively modulated the response to female pheromones in NL3R451C mice. This study is the first to show altered mating behavior in the NL3R451C mouse and has provided new insights into the aggressive phenotype in this model.

BACKGROUND: Aggression is common in patients with autism spectrum disorders (ASD) along with the core symptoms of impairments in social communication and repetitive behavior. Risperidone, an atypical antipsychotic, is widely used to treat aggression in ASD. In order to understand the neurobiological underpinnings of these challenging behaviors, a thorough characterisation of behavioral endophenotypes in animal models is required.
METHODS: We investigated aggression in mice containing the ASD-associated R451C (arginine to cysteine residue 451 substitution) mutation in neuroligin-3 (NL3). Furthermore, we sought to verify social interaction impairments and assess olfaction, anxiety, and repetitive and restrictive behavior in NL3R451C mutant mice.
RESULTS: We show a pronounced elevation in aggressive behavior in NL3R451C mutant mice. Treatment with risperidone reduced this aggression to wild-type (WT) levels. Juvenile and adult social interactions were also investigated, and subtle differences in initiation of interaction were seen in juvenile NL3R451C mice. No genotype differences in olfactory discrimination or anxiety were observed indicating that aggression was not dependent on altered olfaction, stress response, or social preference. We also describe repetitive behavior in NL3R451C mice as assessed by a clinically relevant object exploration task.
CONCLUSIONS: The presence of aberrant aggression and other behavioral phenotypes in NL3R451C mice consistent with clinical traits strengthen face validity of this model of ASD. Furthermore, we demonstrate predictive validity in this model through the reversal of the aggressive phenotype with risperidone. This is the first demonstration that risperidone can ameliorate aggression in an animal model of ASD and will inform mechanistic and therapeutic research into the neurobiology underlying abnormal behaviors in ASD.

Epilepsy is a common comorbidity in patients with autism spectrum disorder (ASD) and several gene mutations are associated with both of these disorders. In order to determine whether a point mutation in the gene for the synaptic protein, Neuroligin-3 (Nlgn3, R451C), identified in patients with ASD alters seizure susceptibility, we administered the proconvulsant pentylenetetrazole (PTZ) to adult male Neuroligin-3(R451C) (NL3(R451C)) and wild type (WT) mice. It has previously been reported that NL3(R451C) mice show altered inhibitory GABAergic activity in brain regions relevant to epilepsy, including the hippocampus and somatosensory cortex. PTZ administration induces absence-seizures at low dose, and generalised convulsive seizures at higher dose. Susceptibility to absence seizures was examined by analysing the frequency and duration of spike-and-wave discharge (SWD) events and accompanying motor seizure activity induced by subcutaneous administration of low dosage (20 or 30mg/kg) PTZ. Susceptibility to generalised convulsive seizures was tested by measuring the response to high dosage (60mg/kg) PTZ using a modified Racine scale. There was no change in the number of SWD events exhibited by NL3(R451C) compared to WT mice following administration of both 20mg/kg PTZ (1.17+/-0.31 compared to 16.0+/-11.16 events/30min, NL3(R451C) versus WT, respectively) and 30mg/kg PTZ (7.5+/-6.54 compared with 27.8+/-19.9 events/30min, NL3(R451C) versus WT, respectively). NL3(R451C) mice were seizure resistant to generalised convulsive seizures induced by high dose PTZ compared to WT littermates (median latency to first >3s duration clonic seizure; 14.5min versus 7.25min, 95% CI: 1.625-2.375, p=0.0009, NL3(R451C) versus WT, respectively). These results indicate that the R451C mutation in the Nlgn3 gene, associated with ASD in humans, confers resistance to induced seizures, suggesting dysfunction of PTZ-sensitive GABAergic signalling in this mouse model of ASD.

Multiple candidate genes have been identified for autism spectrum disorders. While some of these genes reach genome-wide significance, others, such as the R451C point mutation in the synaptic cell adhesion molecule neuroligin-3, appear to be rare. Interestingly, two brothers with the same R451C point mutation in neuroligin-3 present clinically on seemingly disparate sides of the autism spectrum. These clinical findings suggest genetic background may play a role in modifying the penetrance of a particular autism-associated mutation. Animal models may contribute additional support for such mutations as functionally relevant and can provide mechanistic insights. Previously, in collaboration with the Sudhof laboratory, we reported that mice with an R451C substitution in neuroligin-3 displayed social deficits and enhanced spatial learning. While some of these behavioral abnormalities have since been replicated independently in the Sudhof laboratory, observations from the Crawley laboratory failed to replicate these findings in a similar neuroligin-3 mutant mouse model and suggested that genetic background may contribute to variation in observations across laboratories. Therefore, we sought to replicate our findings in the neuroligin-3 R451C point mutant knock-in mouse model (NL3R451C) in a different genetic background. We backcrossed our NL3R451C mouse line onto a 129S2/SvPasCrl genetic background and repeated a subset of our previous behavioral testing. NL3R451C mice on a 129S2/SvPasCrl displayed social deficits, enhanced spatial learning, and increased locomotor activity. These data extend our previous findings that NL3R451C mice exhibit autism-relevant behavioral abnormalities and further suggest that different genetic backgrounds can modify this behavioral phenotype through epistatic genetic interactions. Autism Res 2014, 7: 264-272. (c) 2014 International Society for Autism Research, Wiley Periodicals, Inc.

Neuroligin-3 is a member of the class of cell adhesion proteins that mediate synapse development and have been implicated in autism. Mice with the human R451C mutation (NL3), identical to the point mutation found in two brothers with autism spectrum disorders, were generated and phenotyped in multiple behavioral assays with face validity to the diagnostic symptoms of autism. No differences between NL3 and their wildtype (WT) littermate controls were detected on measures of juvenile reciprocal social interaction, adult social approach, cognitive abilities, and resistance to change in a spatial habit, findings which were replicated in several cohorts of males and females. Physical and procedural abilities were similar across genotypes on measures of general health, sensory abilities, sensorimotor gating, motor functions, and anxiety-related traits. Minor developmental differences were detected between NL3 and WT, including slightly different rates of somatic growth, slower righting reflexes at postnatal days 2-6, faster homing reflexes in females, and less vocalizations on postnatal day 8 in males. Significant differences in NL3 adults included somewhat longer latencies to fall from the rotarod, less vertical activity in the open field, and less acoustic startle to high decibel tones. The humanized R451C mutation in mice did not result in apparent autism-like phenotypes, but produced detectable functional consequences that may be interpreted in terms of physical development and/or reduced sensitivity to stimuli.

Only a small proportion of the mouse genome is transcribed into mature messenger RNA transcripts. There is an international collaborative effort to identify all full-length mRNA transcripts from the mouse, and to ensure that each is represented in a physical collection of clones. Here we report the manual annotation of 60,770 full-length mouse complementary DNA sequences. These are clustered into 33,409 'transcriptional units', contributing 90.1% of a newly established mouse transcriptome database. Of these transcriptional units, 4,258 are new protein-coding and 11,665 are new non-coding messages, indicating that non-coding RNA is a major component of the transcriptome. 41% of all transcriptional units showed evidence of alternative splicing. In protein-coding transcripts, 79% of splice variations altered the protein product. Whole-transcriptome analyses resulted in the identification of 2,431 sense-antisense pairs. The present work, completely supported by physical clones, provides the most comprehensive survey of a mammalian transcriptome so far, and is a valuable resource for functional genomics.

The molecular mechanisms that drive glia-glial interactions and glia-neuronal interactions during the development of the nervous system are poorly understood. A number of membrane-bound cell adhesion molecules have been shown to play a role, although the precise nature of their involvement is unknown. One class of molecules with cell adhesive properties used in the nervous system is the serine-esterase-like family of transmembrane proteins. A member of this class, a glia-specific protein called gliotactin, has been shown to be necessary for the development of the glial sheath in the peripheral nervous system of Drosophila melanogaster. Gliotactin is essential for the development of septate junctions in the glial sheath of individual and neighboring glia. Mutations that remove this protein result in paralysis and eventually death due to a breakdown in the glial-based blood-nerve barrier. To study the role of gliotactin during vertebrate nervous system development, we have isolated a potential vertebrate gliotactin homologue from mice and rat and found that it corresponds to neuroligin 3. Using a combination of RT-PCR and immunohistochemistry, we have found that neuroligin 3 is expressed during the development of the nervous system in many classes of glia. In particular neuroligin 3 is expressed in the olfactory ensheathing glia, retinal astrocytes, Schwann cells, and spinal cord astrocytes in the developing embryo. This expression is developmentally controlled such that in postnatal and adult stages, neuroligin 3 continues to be expressed at high levels in the olfactory ensheathing glia, a highly plastic class of glia that retain many of their developmental characteristics throughout life.