Although many genes predisposing to autism spectrum disorders (ASD) have been identified, the biological mechanism(s) remain unclear. Mouse models based on human disease-causing mutations provide the ...potential for understanding gene function and novel treatment development. Here, we characterize a mouse knockout of the
Cntnap2 gene, which is strongly associated with ASD and allied neurodevelopmental disorders.
Cntnap2
−/−
mice show deficits in the three core ASD behavioral domains, as well as hyperactivity and epileptic seizures, as have been reported in humans with
CNTNAP2 mutations. Neuropathological and physiological analyses of these mice before the onset of seizures reveal neuronal migration abnormalities, reduced number of interneurons, and abnormal neuronal network activity. In addition, treatment with the FDA-approved drug risperidone ameliorates the targeted repetitive behaviors in the mutant mice. These data demonstrate a functional role for
CNTNAP2 in brain development and provide a new tool for mechanistic and therapeutic research in ASD.
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► The
Cntnap2
−/−
mouse model of ASD shows striking parallels with the human disease ► CNTNAP2 affects the development of neuronal circuits, including GABAergic neurons ► Our results support a role for neuronal synchrony in the pathophysiology of ASD ► This model permits dissociation of the circuitries involved in ASD core behaviors
Existing mouse models of autism often fail to capture important aspects of human disease. Mice lacking expression of a neurexin exhibit striking parallels with autism spectrum disorders, recapitulating the key behaviors, neuroanatomical defects, and pharmacological responses of human patients.
Abnormal mTOR Activation in Autism Winden, Kellen D; Ebrahimi-Fakhari, Darius; Sahin, Mustafa
Annual review of neuroscience,
07/2018, Letnik:
41, Številka:
1
Journal Article
Recenzirano
The mechanistic target of rapamycin (mTOR) is an important signaling hub that integrates environmental information regarding energy availability and stimulates anabolic molecular processes and cell ...growth. Abnormalities in this pathway have been identified in several syndromes in which autism spectrum disorder (ASD) is highly prevalent. Several studies have investigated mTOR signaling in developmental and neuronal processes that, when dysregulated, could contribute to the development of ASD. Although many potential mechanisms still remain to be fully understood, these associations are of great interest because of the clinical availability of mTOR inhibitors. Clinical trials evaluating the efficacy of mTOR inhibitors to improve neurodevelopmental outcomes have been initiated.
Progranulin (GRN) mutations cause frontotemporal dementia (FTD), but GRN's function in the CNS remains largely unknown. To identify the pathways downstream of GRN, we used weighted gene coexpression ...network analysis (WGCNA) to develop a systems-level view of transcriptional alterations in a human neural progenitor model of GRN-deficiency. This highlighted key pathways such as apoptosis and ubiquitination in GRN deficient human neurons, while revealing an unexpected major role for the Wnt signaling pathway, which was confirmed by analysis of gene expression data from postmortem FTD brain. Furthermore, we observed that the Wnt receptor Fzd2 was one of only a few genes upregulated at 6 weeks in a GRN knockout mouse, and that FZD2 reduction caused increased apoptosis, while its upregulation promoted neuronal survival in vitro. Together, these in vitro and in vivo data point to an adaptive role for altered Wnt signaling in GRN deficiency-mediated FTD, representing a potential therapeutic target.
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► GRN loss causes apoptosis and loss of neurons in human NPC cultures ► GRN deficiency upregulates Wnt signaling machinery both in vitro and in vivo ► Wnt signaling is the first dysregulated pathway associated with GRN deficiency ► FZD2 upregulation is an immediate and early consequence of GRN loss
Reciprocal copy number variations (CNVs) of 16p11.2 are associated with a wide spectrum of neuropsychiatric and neurodevelopmental disorders. Here, we use human induced pluripotent stem cells ...(iPSCs)-derived dopaminergic (DA) neurons carrying CNVs of 16p11.2 duplication (16pdup) and 16p11.2 deletion (16pdel), engineered using CRISPR-Cas9. We show that 16pdel iPSC-derived DA neurons have increased soma size and synaptic marker expression compared to isogenic control lines, while 16pdup iPSC-derived DA neurons show deficits in neuronal differentiation and reduced synaptic marker expression. The 16pdel iPSC-derived DA neurons have impaired neurophysiological properties. The 16pdel iPSC-derived DA neuronal networks are hyperactive and have increased bursting in culture compared to controls. We also show that the expression of RHOA is increased in the 16pdel iPSC-derived DA neurons and that treatment with a specific RHOA-inhibitor, Rhosin, rescues the network activity of the 16pdel iPSC-derived DA neurons. Our data suggest that 16p11.2 deletion-associated iPSC-derived DA neuron hyperactivation can be rescued by RHOA inhibition.
Tuberous sclerosis complex (TSC) is a genetic disorder caused by mutations in
or
Patients frequently have epilepsy, autism spectrum disorder, and/or intellectual disability, as well as other systemic ...manifestations. In this study, we differentiated human induced pluripotent stem cells (iPSCs) from a female patient with TSC with one or two mutations in
into neurons using induced expression of NGN2 to examine neuronal dysregulation associated with the neurological symptoms in TSC. Using this method, neuronal differentiation was comparable between the three genotypes of iPSCs. We observed that
neurons show mTOR complex 1 (mTORC1) hyperactivation and associated increased cell body size and process outgrowth, as well as exacerbation of the abnormalities by loss of the second allele of
in
neurons. Interestingly, iPSC-derived neurons with either a single or biallelic mutation in
demonstrated hypersynchrony and downregulation of FMRP targets. However, only neurons with biallelic mutations of
demonstrated hyperactivity and transcriptional dysregulation observed in cortical tubers. These data demonstrate that loss of one allele of
is sufficient to cause some morphological and physiological changes in human neurons but that biallelic mutations in
are necessary to induce gene expression dysregulation present in cortical tubers. Finally, we found that treatment of iPSC-derived neurons with rapamycin reduced neuronal activity and partially reversed gene expression abnormalities, demonstrating that mTOR dysregulation contributes to both phenotypes. Therefore, biallelic mutations in
and associated molecular dysfunction, including mTOR hyperactivation, may play a role in the development of cortical tubers.
In this study, we examined neurons derived from induced pluripotent stem cells with two, one, or no functional
(tuberous sclerosis complex 2) alleles and found that loss of one or both alleles of
results in mTORC1 hyperactivation and specific neuronal abnormalities. However, only biallelic mutations in
resulted in elevated neuronal activity and upregulation of cell adhesion genes that is also observed in cortical tubers. These data suggest that loss of heterozygosity of
or
may play an important role in the development of cortical tubers, and potentially epilepsy, in patients with TSC.
Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a neurometabolic disorder caused by ALDH5A1 mutations presenting with autism and epilepsy. SSADHD leads to impaired GABA metabolism and ...results in accumulation of GABA and γ-hydroxybutyrate (GHB), which alter neurotransmission and are thought to lead to neurobehavioral symptoms. However, why increased inhibitory neurotransmitters lead to seizures remains unclear. We used induced pluripotent stem cells from SSADHD patients (one female and two male) and differentiated them into GABAergic and glutamatergic neurons. SSADHD iGABA neurons show altered GABA metabolism and concomitant changes in expression of genes associated with inhibitory neurotransmission. In contrast, glutamatergic neurons display increased spontaneous activity and upregulation of mitochondrial genes. CRISPR correction of the pathogenic variants or SSADHD mRNA expression rescue various metabolic and functional abnormalities in human neurons. Our findings uncover a previously unknown role for SSADHD in excitatory human neurons and provide unique insights into the cellular and molecular basis of SSADHD and potential therapeutic interventions.
Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder, but new therapies have been impeded by a lack of understanding of the pathological mechanisms. Tuberous sclerosis ...complex (TSC) and fragile X syndrome are associated with alterations in the mechanistic target of rapamycin (mTOR) and fragile X messenger ribonucleoprotein 1 (FMRP), which have been implicated in the development of ASD. Previously, we observed that transcripts associated with FMRP were down-regulated in TSC2-deficient neurons. In this study, we find that FMRP turnover is dysregulated in TSC2-deficient rodent primary neurons and human induced pluripotent stem cell (iPSC)-derived neurons and is dependent on the E3 ubiquitin ligase anaphase-promoting complex. We also demonstrate that overexpression of FMRP can partially rescue hyperexcitability in TSC2-deficient iPSC-derived neurons. These data indicate that FMRP dysregulation represents an important pathological mechanism in the development of abnormal neuronal activity in TSC and illustrate a molecular convergence between these two neurogenetic disorders.
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•FMRP degradation is increased in TSC2-deficient rodent and human neurons•Degradation is associated with increased ubiquitination and reduced phosphorylation•Preventing anaphase-promoting complex recognition normalizes FMRP degradation•Overexpression of FMRP in TSC2−/− human neurons reduces spontaneous hyperactivity
In this study, Winden et al. examine how loss of TSC2 in neurons dysregulates FMRP. They found that loss of TSC2 led to increased degradation of FMRP through ubiquitination mediated by the anaphase-promoting complex. In addition, they show that overexpression of FMRP can reduce spontaneous hyperactivity in TSC-deficient human neurons.
Rheumatoid arthritis is a systemic autoimmune disease, but disease flares typically affect only a subset of joints, distributed in a distinctive pattern for each patient. Pursuing this intriguing ...pattern, we show that arthritis recurrence is mediated by long-lived synovial resident memory T cells (TRM). In three murine models, CD8+ cells bearing TRM markers remain in previously inflamed joints during remission. These cells are bona fide TRM, exhibiting a failure to migrate between joints, preferential uptake of fatty acids, and long-term residency. Disease flares result from TRM activation by antigen, leading to CCL5-mediated recruitment of circulating effector cells. Correspondingly, TRM depletion ameliorates recurrence in a site-specific manner. Human rheumatoid arthritis joint tissues contain a comparable CD8+-predominant TRM population, which is most evident in late-stage leukocyte-poor synovium, exhibiting limited T cell receptor diversity and a pro-inflammatory transcriptomic signature. Together, these findings establish synovial TRM as a targetable mediator of disease chronicity in autoimmune arthritis.
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•Arthritic human and murine joints acquire CD8+ resident memory T cells (TRM)•TRM from rheumatoid joints display a restricted T cell receptor repertoire•Antigen-activated TRM recruit other immune cells to cause an arthritis flare•Depletion of synovial TRM blocks local disease recurrence
Rheumatoid arthritis is characterized by recurrent inflammation of some, but not all, joints. Chang et al. show that CD8+ tissue-resident memory T cells accumulate in previously inflamed joints, nucleating local disease recurrence when triggered by antigens. TRM depletion attenuates arthritis flares, defining a mechanistic basis for joint-specific memory.
Neither the molecular basis of the pathologic tendency of neuronal circuits to generate spontaneous seizures (epileptogenicity) nor anti-epileptogenic mechanisms that maintain a seizure-free state ...are well understood. Here, we performed transcriptomic analysis in the intrahippocampal kainate model of temporal lobe epilepsy in rats using both Agilent and Codelink microarray platforms to characterize the epileptic processes. The experimental design allowed subtraction of the confounding effects of the lesion, identification of expression changes associated with epileptogenicity, and genes upregulated by seizures with potential homeostatic anti-epileptogenic effects. Using differential expression analysis, we identified several hundred expression changes in chronic epilepsy, including candidate genes associated with epileptogenicity such as Bdnf and Kcnj13. To analyze these data from a systems perspective, we applied weighted gene co-expression network analysis (WGCNA) to identify groups of co-expressed genes (modules) and their central (hub) genes. One such module contained genes upregulated in the epileptogenic region, including multiple epileptogenicity candidate genes, and was found to be involved the protection of glial cells against oxidative stress, implicating glial oxidative stress in epileptogenicity. Another distinct module corresponded to the effects of chronic seizures and represented changes in neuronal synaptic vesicle trafficking. We found that the network structure and connectivity of one hub gene, Sv2a, showed significant changes between normal and epileptogenic tissue, becoming more highly connected in epileptic brain. Since Sv2a is a target of the antiepileptic levetiracetam, this module may be important in controlling seizure activity. Bioinformatic analysis of this module also revealed a potential mechanism for the observed transcriptional changes via generation of longer alternatively polyadenlyated transcripts through the upregulation of the RNA binding protein HuD. In summary, combining conventional statistical methods and network analysis allowed us to interpret the differentially regulated genes from a systems perspective, yielding new insight into several biological pathways underlying homeostatic anti-epileptogenic effects and epileptogenicity.
16p13.11 copy number variants (CNVs) have been associated with autism, schizophrenia, psychosis, intellectual disability, and epilepsy. The majority of 16p13.11 deletions or duplications occur within ...three well-defined intervals, and despite growing knowledge of the functions of individual genes within these intervals, the molecular mechanisms that underlie commonly observed clinical phenotypes remain largely unknown. Patient-derived, induced pluripotent stem cells (iPSCs) provide a platform for investigating the morphological, electrophysiological, and gene-expression changes that result from 16p13.11 CNVs in human-derived neurons. Patient derived iPSCs with varying sizes of 16p13.11 deletions and familial controls were differentiated into cortical neurons for phenotypic analysis. High-content imaging and morphological analysis of patient-derived neurons demonstrated an increase in neurite branching in patients compared with controls. Whole-transcriptome sequencing revealed expression level changes in neuron development and synaptic-related gene families, suggesting a defect in synapse formation. Subsequent quantification of synapse number demonstrated increased numbers of synapses on neurons derived from early-onset patients compared to controls. The identification of common phenotypes among neurons derived from patients with overlapping 16p13.11 deletions will further assist in ascertaining common pathways and targets that could be utilized for screening drug candidates. These studies can help to improve future treatment options and clinical outcomes for 16p13.11 deletion patients.
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