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Targeted therapy with galantamine in a pediatric patient with 15q13.3 deletion syndrome
... Similarly, there are reports of individuals with 15q13.3 deletion syndrome associated with schizophrenia, intellectual disability, epilepsy, aggression and autism spectrum disorders (ASD) where CHRNA7, the gene encoding the α7-nicotinic acetylcholine receptor subunit, is deleted (Casas-Alba et al., 2021;Cubells et al., 2011). The acetylcholinesterase inhibitor, galantamine, was observed to reduce aggression in one adult with psychosis and intellectual disability (Cubells et al., 2011) and improve fluid reasoning, working memory, and processing speed in one youth with ASD (Casas-Alba et al., 2021). ...
... deletion syndrome associated with schizophrenia, intellectual disability, epilepsy, aggression and autism spectrum disorders (ASD) where CHRNA7, the gene encoding the α7-nicotinic acetylcholine receptor subunit, is deleted (Casas-Alba et al., 2021;Cubells et al., 2011). The acetylcholinesterase inhibitor, galantamine, was observed to reduce aggression in one adult with psychosis and intellectual disability (Cubells et al., 2011) and improve fluid reasoning, working memory, and processing speed in one youth with ASD (Casas-Alba et al., 2021). ...
... Second, it may help elucidate the pathophysiology of psychiatric disorders through the mechanistic study of pathogenic CNVs [26]. Third, it may provide targeted treatment and practical guidelines to treat patients with pathogenic CNVs in clinical settings [27][28][29][30]. ...
Rare copy number variations (CNVs) are part of the genetics of schizophrenia; they are highly heterogeneous and personalized. The CNV Analysis Group of the Psychiatric Genomic Consortium (PGC) conducted a large-scale analysis and discovered that recurrent CNVs at eight genetic loci were pathogenic to schizophrenia, including 1q21.1, 2p16.3 (NRXN1), 3q29, 7q11.23, 15q13.3, distal 16p11.2, proximal 16p11.2, and 22q11.2. We adopted a two-stage strategy to translate this knowledge into clinical psychiatric practice. As a screening test, we first developed a real-time quantitative PCR (RT-qPCR) panel that simultaneously detected these pathogenic CNVs. Then, we tested the utility of this screening panel by investigating a sample of 557 patients with schizophrenia. Chromosomal microarray analysis (CMA) was used to confirm positive cases from the screening test. We detected and confirmed thirteen patients who carried CNVs at these hot loci, including two patients at 1q21.1, one patient at 7q11.2, three patients at 15q13.3, two patients at 16p11.2, and five patients at 22q11.2. The detection rate in this sample was 2.3%, and the concordance rate between the RT-qPCR test panel and CMA was 100%. Our results suggest that a two-stage approach is cost-effective and reliable in achieving etiological diagnosis for some patients with schizophrenia and improving the understanding of schizophrenia genetics.
Recurrent copy number variations (CNVs) are common causes of neurodevelopmental disorders (NDDs) and associated with a range of psychiatric traits. These CNVs occur at defined genomic regions that are particularly prone to recurrent deletions and duplications and often exhibit variable expressivity and incomplete penetrance. Robust estimates of the population prevalence and inheritance pattern of recurrent CNVs associated with neurodevelopmental disorders (NDD CNVs) are lacking. Here we perform array-based CNV calling in 12,252 mother–father–child trios from the Norwegian Mother, Father, and Child Cohort Study (MoBa) and analyse the inheritance pattern of 26 recurrent NDD CNVs in 13 genomic regions. We estimate the total prevalence of recurrent NDD CNVs (duplications and deletions) in live-born children to 0.48% (95% C.I.: 0.37–0.62%), i.e., ~1 in 200 newborns has either a deletion or duplication in these NDDs associated regions. Approximately a third of the newborn recurrent NDD CNVs (34%, N = 20/59) are de novo variants. We provide prevalence estimates and inheritance information for each of the 26 NDD CNVs and find higher prevalence than previously reported for 1q21.1 deletions (~1:2000), 15q11.2 duplications (~1:4000), 15q13.3 microdeletions (~1:2500), 16p11.2 proximal microdeletions (~1:2000) and 17q12 deletions (~1:4000) and lower than previously reported prevalence for the 22q11.2 deletion (~1:12,000). In conclusion, our analysis of an unselected and representative population of newborns and their parents provides a clearer picture of the rate of recurrent microdeletions/duplications implicated in neurodevelopmental delay. These results will provide an important resource for genetic diagnostics and counseling.
Copy-number variants (CNVs) of chromosome 15q13.3 manifest clinically as neuropsychiatric disorders with variable expressivity. CHRNA7, encoding for the α7 nicotinic acetylcholine receptor (nAChR), has been suggested as a candidate gene for the phenotypes observed. Here, we used induced pluripotent stem cells (iPSCs) and neural progenitor cells (NPCs) derived from individuals with heterozygous 15q13.3 deletions and heterozygous 15q13.3 duplications to investigate the CHRNA7-dependent molecular consequences of the respective CNVs. Unexpectedly, both deletions and duplications lead to decreased α7 nAChR-associated calcium flux. For deletions, this decrease in α7 nAChR-dependent calcium flux is expected due to haploinsufficiency of CHRNA7. For duplications, we found that increased expression of CHRNA7 mRNA is associated with higher expression of nAChR-specific and resident ER chaperones, indicating increased ER stress. This is likely a consequence of inefficient chaperoning and accumulation of α7 subunits in the ER, as opposed to being incorporated into functional α7 nAChRs at the cell membrane. Here, we showed that α7 nAChR-dependent calcium signal cascades are downregulated in both 15q13.3 deletion and duplication NPCs. While it may seem surprising that genomic changes in opposite direction have consequences on downstream pathways that are in similar direction, it aligns with clinical data, which suggest that both individuals with deletions and duplications of 15q13.3 manifest neuropsychiatric disease and cognitive deficits.
The alpha-7 nicotinic acetylcholine receptor (α7 nAChR), consisting of homomeric α7 subunits, is a ligand-gated Ca²⁺-permeable ion channel implicated in cognition and neuropsychiatric disorders. Enhancement of α7 nAChR function is considered to be a potential therapeutic strategy aiming at ameliorating cognitive deficits of neuropsychiatric disorders such as Alzheimer's disease (AD) and schizophrenia. Currently, a number of α7 nAChR modulators have been reported and several of them have advanced into clinical trials. In this brief review, we outline recent progress made in understanding the role of the α7 nAChR in multiple neuropsychiatric disorders and the pharmacological effects of α7 nAChR modulators used in clinical trials. © 2017 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences.
The alpha7 nicotinic acetylcholine receptor, encoded by the CHRNA7 gene, has been implicated in various psychiatric and behavioral disorders, including schizophrenia, bipolar disorder, epilepsy, autism, Alzheimer’s disease, and Parkinson’s disease, and is considered a potential target for therapeutic intervention. 15q13.3 microdeletion syndrome is a rare genetic disorder, caused by submicroscopic deletions on chromosome 15q. CHRNA7 is the only gene in this locus that has been deleted entirely in cases involving the smallest microdeletions. Affected individuals manifest variable neurological and behavioral phenotypes, which commonly include developmental delay/intellectual disability, epilepsy, and autism spectrum disorder. Subsets of patients have short attention spans, aggressive behaviors, mood disorders, or schizophrenia. Previous behavioral studies suggested that Chrna7 deficient mice had attention deficits, but were normal in baseline behavioral responses, learning, memory, and sensorimotor gating. Given a growing interest in CHRNA7-related diseases and a better appreciation of its associated human phenotypes, an in-depth behavioral characterization of the Chrna7 deficient mouse model appeared prudent. This study was designed to investigate whether Chrna7 deficient mice manifest phenotypes related to those seen in human individuals, using an array of 12 behavioral assessments and electroencephalogram (EEG) recordings on freely-moving mice. Examined phenotypes included social interaction, compulsive behaviors, aggression, hyperactivity, anxiety, depression, and somatosensory gating. Our data suggests that mouse behavior and EEG recordings are not sensitive to decreased Chrna7 copy number.
Mutation of human chromosome 15q13.3 increases the risk for autism and schizophrenia. One of the noteworthy genes in 15q13.3 is CHRNA7, which encodes the nicotinic acetylcholine receptor alpha 7 subunit (α7nAChR) associated with schizophrenia in clinical studies and rodent models. This study investigates the role of α7nAChR in maternal immune activation (MIA) mice model, a murine model of environmental risk factor for autism and schizophrenia. We provided choline, a selective α7nAChR agonist among its several developmental roles, in the diet of C57BL/6N wild-type dams throughout the gestation and lactation period and induced MIA at mid-gestation. The adult offspring behavior and gene expression profile in the maternal splenic-placenta-fetal brain axis at mid-gestation were investigated. We found that choline supplementation prevented several MIA behavioral abnormalities in the wild-type offspring. Pro-inflammatory cytokine interleukin-6 (IL-6) and Chrna7 gene expression in the wild-type fetal brain were elevated by poly(I:C) injection and were suppressed by gestational choline supplementation. We further investigated the gene expression level of IL-6 in Chrna7 mutant mice. We found that the basal level of IL-6 was higher in Chrna7 mutant fetal brain, which suggests that α7nAChR may serve an anti-inflammatory role in the fetal brain during development. Lastly, we induced MIA in Chrna7(+/-) offspring. The Chrna7(+/-) offspring were more vulnerable to MIA, with increased behavioral abnormalities. Our study shows that α7nAChR modulates inflammatory response affecting the fetal brain and demonstrates its effects on offspring behavior development after maternal infection.
Copyright © 2015 Elsevier Inc. All rights reserved.
The role of cholinergic abnormalities in autism was recently evidenced and there is a growing interest in cholinergic modulation, emerging for targeting autistic symptoms. Galantamine is an acetylcholinesterase inhibitor and an allosteric potentiator of nicotinic receptors. This study aimed to evaluate the possible effects of galantamine as an augmentative therapy to risperidone, in autistic children. In this randomized, double-blind, placebo-controlled, parallel-group study, 40 outpatients aged 4-12 years whom had a diagnosis of autism (DSM IV-TR) and a score of 12 or higher on the Aberrant Behavior Checklist-Community (ABC-C) Irritability subscale were equally randomized to receive either galantamine (up to 24 mg/day) or placebo, in addition to risperidone (up to 2 mg/day), for 10 weeks. We rated participants by ABC-C and a side effects checklist, at baseline and at weeks 5 and 10. By the study endpoint, the galantamine-treated patients showed significantly greater improvement in the Irritability (P = 0.017) and Lethargy/Social Withdrawal (P = 0.005) subscales than the placebo group. The difference between the two groups in the frequency of side effects was not significant. In conclusion, galantamine augmentation was shown to be a relatively effective and safe augmentative strategy for alleviating some of the autism-related symptoms.
Multiple genomic disorders result from recurrent deletions or duplications between low copy repeat (LCR) clusters, mediated by nonallelic homologous recombination. These copy number variants (CNVs) often exhibit variable expressivity and/or incomplete penetrance. However, the population prevalence of many genomic disorders has not been estimated accurately. A subset of genomic disorders similarly characterized by CNVs between LCRs have been studied epidemiologically, including Williams-Beuren syndrome (7q11.23), Smith-Magenis syndrome (17p11.2), velocardiofacial syndrome (22q11.21), Prader-Willi/Angelman syndromes (15q11.2q12), 17q12 deletion syndrome, and Charcot-Marie-Tooth neuropathy type 1/hereditary neuropathy with liability to pressure palsy (PMP22, 17q11.2). We have generated a method to estimate prevalence of highly penetrant genomic disorders by (1) leveraging epidemiological data for genomic disorders with previously reported prevalence estimates, (2) obtaining chromosomal microarray data on genomic disorders from a large medical genetics clinic; and (3) utilizing these in a linear regression model to determine the prevalence of this syndromic copy number change among the general population. Using our algorithm, the prevalence for five clinically relevant recurrent genomic disorders: 1q21.1 microdeletion (1/6882 live births) and microduplication syndromes (1/6309), 15q13.3 microdeletion syndrome (1/5525), and 16p11.2 microdeletion (1/3021) and microduplication syndromes (1/4216), were determined. These findings will inform epidemiological strategies for evaluating those conditions, and our method may be useful to evaluate the prevalence of other highly penetrant genomic disorders.
Abnormalities in CHRNA7, the alpha7-nicotinic receptor gene, have been reported in autism spectrum disorder. These genetic abnormalities potentially decrease the receptor’s expression and diminish its functional role. This double-blind, placebo-controlled crossover study in two adult patients investigated whether an investigational receptor-specific partial agonist drug would increase the inhibitory functions of the gene and thereby increase patients’ attention. An electrophysiological biomarker, P50 inhibition, verified the intended neurobiological effect of the agonist, and neuropsychological testing verified a primary cognitive effect. Both patients perceived increased attention in their self-ratings. Alpha7-nicotinic receptor agonists, currently the target of drug development in schizophrenia and Alzheimer Disease, may also have positive clinical effects in autism spectrum disorder.
Epilepsy is associated with several psychiatric disorders, including cognitive impairment, autism and attention deficit/hyperactivity disorder (ADHD). However, the psychopathology of epilepsy is frequently unrecognized and untreated in patients. In the present study, we investigated the effects of ABT-418, a neuronal nicotinic acetylcholine receptor agonist, on pentylenetetrazol (PTZ)-kindled mice with behavioral and motor abnormalities. PTZ-kindled mice displayed impaired motor coordination (in the rotarod test), anxiety (in the elevated plus maze test) and social approach impairment (in the three-chamber social test) compared with control mice. ABT-418 treatment (0.05 mg/kg, intraperitoneally) alleviated these behavioral abnormalities in PTZ-kindled mice. Immunolabeling of tissue sections demonstrated that expression of the α4 nicotinic acetylcholine receptor subunit in the medial habenula was similar in control and PTZ-kindled mice. However, expression was significantly decreased in the piriform cortex in PTZ-kindled mice. In addition, we examined the expression of the synaptic adhesion molecule neuroligin 3 (NLG3). NLG3 expression in the piriform cortex was significantly higher in PTZ-kindled mice compared with control mice. Collectively, our findings suggest that ADHD-like or autistic-like behavioral abnormalities associated with epilepsy are closely related to the downregulation of the α4 nicotinic receptor and the upregulation of NLG3 in the piriform cortex. In summary, this study indicates that ABT-418 might have therapeutic potential for attentional impairment in epileptic patients with psychiatric disorders such as autism and ADHD.
Array comparative genomic hybridization (array CGH) has led to the identification of microdeletions of the proximal region of chromosome 15q between breakpoints (BP) 3 or BP4 and BP5 encompassing CHRNA7, the gene encoding the α7-nicotinic acetylcholine receptor (α7nAChR) subunit. Phenotypic manifestations of persons with these microdeletions are variable and some heterozygous carriers are seemingly unaffected, consistent with their variable expressivity and incomplete penetrance. Nonetheless, the 15q13.3 deletion syndrome is associated with several neuropsychiatric disorders, including idiopathic generalized epilepsy, intellectual disability, autism spectrum disorders (ASDs) and schizophrenia. Haploinsufficient expression of CHRNA7 in this syndrome has highlighted important roles the α7nAChR plays in the developing brain and normal processes of attention, cognition, memory and behavior throughout life. Importantly, the existence of the 15q13.3 deletion syndrome contributes to an emerging literature supporting clinical trials therapeutically targeting the α7nAChR in disorders such as ASDs and schizophrenia, including the larger population of patients with no evidence of haploinsufficient expression of CHRNA7. Translational clinical trials will be facilitated by the existence of positive allosteric modulators (PAMs) of the α7nAChR that act at sites on the receptor distinct from the orthosteric site that binds acetylcholine and choline, the receptor's endogenous ligands. PAMs lack intrinsic efficacy by themselves, but act where and when the endogenous ligands are released in response to relevant social and cognitive provocations to increase the likelihood they will result in α7nAChR ion channel activation.
Copyright © 2015. Published by Elsevier Inc.
Purpose:
Recurrent 15q13.3 deletions are enriched in multiple neurodevelopmental conditions including intellectual disability, autism, epilepsy, and schizophrenia. However, the 15q13.3 microdeletion syndrome remains ill-defined.
Methods:
We systematically compiled all cases of 15q13.3 deletion published before 2014. We also examined three locally available cohorts to identify new adults with 15q13.3 deletions.
Results:
We identified a total of 246 cases (133 children, 113 adults) with deletions overlapping or within the 15q13.3 (breakpoint (BP)4-BP5) region, including seven novel adult cases from local cohorts. No BP4-BP5 deletions were identified in 23,838 adult controls. Where known, 15q13.3 deletions were typically inherited (85.4%) and disproportionately of maternal origin (P < 0.0001). Overall, 198 cases (121 children, 77 adults; 80.5%) had at least one neuropsychiatric diagnosis. Accounting for ascertainment, developmental disability/intellectual disability was present in 57.7%, epilepsy/seizures in 28.0%, speech problems in 15.9%, autism spectrum disorder in 10.9%, schizophrenia in 10.2%, mood disorder in 10.2%, and attention deficit hyperactivity disorder in 6.5%. By contrast, major congenital malformations, including congenital heart disease (2.4%), were uncommon. Placenta previa occurred in the pregnancies of four cases.
Conclusion:
The 15q13.3 microdeletion syndrome is predominantly characterized by neuropsychiatric expression. There are implications for pre- and postnatal detection, genetic counseling, and anticipatory care.
15q13.3 deletion syndrome (15q13.3DS) is a common recurrent genomic disorder associated with epilepsy, intellectual impairment, aggressive behavior, schizophrenia, and autism. A 39-year-old male presented with 15q13.3DS, epilepsy, intellectual impairment, psychosis, and recurrent episodes of aggressive rage. We hypothesized that the patient's aggressive behavior reflected deficits in α7 nicotinic cholinergic receptor (NChR)-mediated neurotransmission, arising from haploinsufficiency of the structural gene CHRNA7 due to the deletion. Treatment with the NChR allosteric modulator and acetylcholinesterase (AChE) inhibitor, galantamine, led to a dramatic decline in the frequency and intensity of rage outbursts, suggesting that enhancement of α7 NChR function can ameliorate 15q13.3DS-associated rage outbursts.
Cholinesterase inhibitors are the only approved drug treatment for patients with mild to moderately severe Alzheimer's disease. Interestingly, the clinical potency of these drugs does not correlate well with their activity as cholinesterase inhibitors, nor is their action as short lived as would be expected from purely symptomatic treatment. A few cholinesterase inhibitors, including galantamine, produce beneficial effects even after drug treatment has been terminated. These effects assume modes of action other than mere esterase inhibition and are capable of inducing systemic changes. We have recently discovered a mechanism that could account, at least in part, for the above-mentioned unexpected properties of some cholinesterase inhibitors. We have found that a subgroup of cholinesterase inhibitors, including galantamine but excluding tacrine, directly interacts with nicotinic acetylcholine receptors. These compounds, named allosterically potentiating ligands, sensitize nicotinic receptors by increasing the probability of channel opening induced by acetylcholine and nicotinic agonists and by slowing down receptor desensitization. The allosterically potentiating ligand action, which is not necessarily associated with cholinesterase inhibition, has been demonstrated by whole-cell patch-clamp recordings to occur in natural murine and human neurons and in murine and human cell lines expressing various subtypes of neuronal nicotinic acetylcholine receptors.
In light of the recently reported neuropathologic and neurochemical abnormalities of the cholinergic pathways in autism, donepezil, a cholinesterase inhibitor, is a potentially useful agent in the treatment of cognitive and behavioral symptoms observed in this disorder. A retrospective pilot study was conducted to determine whether donepezil is effective in the treatment of children and adolescents with autism. Eight patients (mean age = 11.0 +/- 4.1 years; range 7-19 years) who met Diagnostic and Statistical Manual of Mental Disorders (4th edition) criteria for autistic disorder were openly treated with donepezil. All patients were on concomitant psychoactive medications. Four of these patients (50%) demonstrated significant improvement as assessed by the Aberrant Behavior Checklist and the Clinical Global Impression Scale. Decreases in the Irritability and Hyperactivity subscales were observed, but no changes in the Inappropriate Speech, Lethargy, and Stereotypies subscales were noted. Limited and transient side effects were reported, with one patient experiencing gastrointestinal disturbances and another reporting mild irritability. Double-blind, placebo-controlled investigations are needed to provide further evidence of the potential benefits of donepezil to patients with autistic disorder.
Autism is a developmental disorder of unknown aetiopathology and lacking any specific pharmacological therapeutic intervention. Neurotransmitters such as serotonin, gamma-aminobutyric acid (GABA) and acetylcholine have been implicated. Abnormalities in nicotinic acetylcholine receptors have been identified including cortical loss of binding to the alpha4/beta2 subtype and increase in cerebellar alpha7 binding. Receptor expression (mRNA) has not so far been systematically examined. This study aims to further explore the role of nicotinic receptors in autism by analysing nicotinic receptor subunit mRNA in conjunction with protein levels and receptor binding in different brain areas. Quantitative RT-PCR for alpha4, alpha7 and beta2 subunit mRNA expression levels; alpha3, alpha4, alpha7 and beta2 subunit protein expression immunochemistry and specific radioligand receptor binding were performed in adult autism and control brain samples from cerebral cortex and cerebellum. Alpha4 and beta2 protein expression and receptor binding density as well as alpha4 mRNA levels were lower in parietal cortex in autism, while alpha7 did not change for any of these parameters. In cerebellum, alpha4 mRNA expression was increased, whereas subunit protein and receptor levels were decreased. Alpha7 receptor binding in cerebellum was increased alongside non-significant elevations in mRNA and protein expression levels. No significant changes were found for beta2 in cerebellum. The data obtained, using complementary measures of receptor expression, indicate that reduced gene expression of the alpha4beta2 nicotinic receptor in the cerebral cortex is a major feature of the neurochemical pathology of autism, whilst post-transcriptional abnormalities of both this and the alpha7 subtype are apparent in the cerebellum. The findings point to dendritic and/or synaptic nicotinic receptor abnormalities that may relate to disruptions in cerebral circuitry development.