Association between early-onset Parkinson disease and 22q11.2 deletion syndrome: identification of a novel genetic form of Parkinson disease and its clinical implications

Salivary α-Synuclein as a Candidate Biomarker of Parkinsonism in 22q11.2 Deletion Syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11.2DS) has been linked to an increased risk of early-onset Parkinson's disease. However, the pathophysiological mechanisms underlying parkinsonism remain poorly understood.

OBJECTIVE

The objective is to investigate salivary total α-synuclein levels in 22q11.2DS patients with and without parkinsonian motor signs.

METHODS

This cross-sectional study included 10 patients with 22q11.2DS with parkinsonism (Park+), ten 22q11.2DS patients without parkinsonism (Park-), and 10 age and sex-comparable healthy subjects (HS). Salivary and serum α-synuclein levels were measured using enzyme-linked immunosorbent assay.

RESULTS

Salivary total α-synuclein concentration was significantly lower in Park (+) patients than in Park (-) patients and HS (P = 0.007). In addition, salivary α-synuclein showed good accuracy in discriminating Park (+) from Park (-) patients (area under the curve = 0.86) and correlated with motor severity and cognitive impairment.

CONCLUSION

This exploratory study suggests that the parkinsonian phenotype of 22q11.2DS is associated with a reduced concentration of monomeric α-synuclein in biological fluids.

The Role of Structural Variants in the Genetic Architecture of Parkinson's Disease

Parkinson's disease (PD) significantly impacts millions of individuals worldwide. Although our understanding of the genetic foundations of PD has advanced, a substantial portion of the genetic variation contributing to disease risk remains unknown. Current PD genetic studies have primarily focused on one form of genetic variation, single nucleotide variants (SNVs), while other important forms of genetic variation, such as structural variants (SVs), are mostly ignored due to the complexity of detecting these variants with traditional sequencing methods. Yet, these forms of genetic variation play crucial roles in gene expression and regulation in the human brain and are causative of numerous neurological disorders, including forms of PD. This review aims to provide a comprehensive overview of our current understanding of the involvement of coding and noncoding SVs in the genetic architecture of PD.

A biological classification of Parkinson's disease: the SynNeurGe research diagnostic criteria

With the hope that disease-modifying treatments could target the molecular basis of Parkinson's disease, even before the onset of symptoms, we propose a biologically based classification. Our classification acknowledges the complexity and heterogeneity of the disease by use of a three-component system (SynNeurGe): presence or absence of pathological α-synuclein (S) in tissues or CSF; evidence of underlying neurodegeneration (N) defined by neuroimaging procedures; and documentation of pathogenic gene variants (G) that cause or strongly predispose to Parkinson's disease. These three components are linked to a clinical component (C), defined either by a single high-specificity clinical feature or by multiple lower-specificity clinical features. The use of a biological classification will enable advances in both basic and clinical research, and move the field closer to the precision medicine required to develop disease-modifying therapies. We emphasise the initial application of these criteria exclusively for research. We acknowledge its ethical implications, its limitations, and the need for prospective validation in future studies.

APOE expression and secretion are modulated by mitochondrial dysfunction

Mitochondria influence cellular function through both cell-autonomous and non-cell autonomous mechanisms, such as production of paracrine and endocrine factors. Here, we demonstrate that mitochondrial regulation of the secretome is more extensive than previously appreciated, as both genetic and pharmacological disruption of the electron transport chain caused upregulation of the Alzheimer's disease risk factor apolipoprotein E (APOE) and other secretome components. Indirect disruption of the electron transport chain by gene editing of SLC25A mitochondrial membrane transporters as well as direct genetic and pharmacological disruption of either complexes I, III, or the copper-containing complex IV of the electron transport chain elicited upregulation of APOE transcript, protein, and secretion, up to 49-fold. These APOE phenotypes were robustly expressed in diverse cell types and iPSC-derived human astrocytes as part of an inflammatory gene expression program. Moreover, age- and genotype-dependent decline in brain levels of respiratory complex I preceded an increase in APOE in the 5xFAD mouse model. We propose that mitochondria act as novel upstream regulators of APOE-dependent cellular processes in health and disease.

The Relationship between Motor Symptoms, Signs, and Parkinsonism with Facial Emotion Recognition Deficits in Individuals with 22q11.2 Deletion Syndrome at High Genetic Risk for Psychosis

Background. The 22q11.2 Deletion Syndrome (22q11.2DS) is a genetic condition at high risk of developing both psychosis and motor disorders. Social Cognition (SC) deficits have been associated not only with schizophrenia but also with Parkinson’s disease (PD). The present study assessed SC deficits in 22q11.2DS and investigated the interaction between motor symptoms and deficits in Facial Emotion Expressions (FEE) recognition and in Theory of Mind (ToM) tasks in people with 22q11.2DS. Methods. We recruited 38 individuals with 22q11.2DS without psychosis ( $N=38$ , DEL) and 18 with 22q11.2DS and psychosis ( $N=18$ , DEL_SCZ). The Positive And Negative Syndrome Scale (PANSS), Ekman’s 60 Faces Test (EK-60F), the Awareness of Social Inference Test (TASIT EmRec), and the Movement Disorder Society-Unified Parkinson’s Disease Rating Scale part III (UPDRS III) were administered. Correlations were sought between UPDRS III and both TASIT EmRec and EK-60F scores. Analyses were conducted separately for each psychopathological subgroup. Results. Higher UPDRS III ( $p=0.04$ ) and lower EK-60F ( $p=0.025$ ) scores were observed in the DEL_SCZ group. We found inverse correlations between UPDRS III and both TASIT EmRec ( $r=-0.289$ , $p=0.031$ ) and EK-60F ( $r=-0.387$ , $p=0.006$ ) scores in the whole sample. Correlations were no longer significant in the DEL_SCZ group (UPDRS III-TASIT EmRec $p=0.629$ ; UPDRS III-EK60F $p=0.933$ ) whilst being stronger in the DEL group (TASIT EmRec, $r=-0.560$ , $p<0.001$ ; EK60F, $r=-0.542$ , $p<0.001$ ). Analyses were adjusted for CPZ Eq and IQ. Conclusions. A modulation between FEE recognition deficits and motor symptoms and signs was observed in the 22q11.2DS group, likely affecting patients’ quality of life.

Updated clinical practice recommendations for managing adults with 22q11.2 deletion syndrome

This review aimed to update the clinical practice guidelines for managing adults with 22q11.2 deletion syndrome (22q11.2DS). The 22q11.2 Society recruited expert clinicians worldwide to revise the original clinical practice guidelines for adults in a stepwise process according to best practices: (1) a systematic literature search (1992-2021), (2) study selection and synthesis by clinical experts from 8 countries, covering 24 subspecialties, and (3) formulation of consensus recommendations based on the literature and further shaped by patient advocate survey results. Of 2441 22q11.2DS-relevant publications initially identified, 2344 received full-text review, with 2318 meeting inclusion criteria (clinical care relevance to 22q11.2DS) including 894 with potential relevance to adults. The evidence base remains limited. Thus multidisciplinary recommendations represent statements of current best practice for this evolving field, informed by the available literature. These recommendations provide guidance for the recognition, evaluation, surveillance, and management of the many emerging and chronic 22q11.2DS-associated multisystem morbidities relevant to adults. The recommendations also address key genetic counseling and psychosocial considerations for the increasing numbers of adults with this complex condition.

Pediatric-Onset Epilepsy and Developmental Epileptic Encephalopathies Followed by Early-Onset Parkinsonism

Genetic early-onset Parkinsonism is unique due to frequent co-occurrence of hyperkinetic movement disorder(s) (MD), or additional neurological of systemic findings, including epilepsy in up to 10-15% of cases. Based on both the classification of Parkinsonism in children proposed by Leuzzi and coworkers and the 2017 ILAE epilepsies classification, we performed a literature review in PubMed. A few discrete presentations can be identified: Parkinsonism as a late manifestation of complex neurodevelopmental disorders, characterized by developmental and epileptic encephalopathies (DE-EE), with multiple, refractory seizure types and severely abnormal EEG characteristics, with or without preceding hyperkinetic MD; Parkinsonism in the context of syndromic conditions with unspecific reduced seizure threshold in infancy and childhood; neurodegenerative conditions with brain iron accumulation, in which childhood DE-EE is followed by neurodegeneration; and finally, monogenic juvenile Parkinsonism, in which a subset of patients with intellectual disability or developmental delay (ID/DD) develop hypokinetic MD between 10 and 30 years of age, following unspecific, usually well-controlled, childhood epilepsy. This emerging group of genetic conditions leading to epilepsy or DE-EE in childhood followed by juvenile Parkinsonism highlights the need for careful long-term follow-up, especially in the context of ID/DD, in order to readily identify individuals at increased risk of later Parkinsonism.

The Impact of Dysregulated microRNA Biogenesis Machinery and microRNA Sorting on Neurodegenerative Diseases

MicroRNAs (miRNAs) are 22-nucleotide noncoding RNAs involved in the differentiation, development, and function of cells in the body by targeting the 3'- untranslated regions (UTR) of mRNAs for degradation or translational inhibition. miRNAs not only affect gene expression inside the cells but also, when sorted into exosomes, systemically mediate the communication between different types of cells. Neurodegenerative diseases (NDs) are age-associated, chronic neurological diseases characterized by the aggregation of misfolded proteins, which results in the progressive degeneration of selected neuronal population(s). The dysregulation of biogenesis and/or sorting of miRNAs into exosomes was reported in several NDs, including Huntington's disease (HD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Alzheimer's disease (AD). Many studies support the possible roles of dysregulated miRNAs in NDs as biomarkers and therapeutic treatments. Understanding the molecular mechanisms underlying the dysregulated miRNAs in NDs is therefore timely and important for the development of diagnostic and therapeutic interventions. In this review, we focus on the dysregulated miRNA machinery and the role of RNA-binding proteins (RBPs) in NDs. The tools that are available to identify the target miRNA-mRNA axes in NDs in an unbiased manner are also discussed.

Genetics and Pathogenesis of Parkinson's Syndrome

Parkinson's disease (PD) is clinically, pathologically, and genetically heterogeneous, resisting distillation to a single, cohesive disorder. Instead, each affected individual develops a virtually unique form of Parkinson's syndrome. Clinical manifestations consist of variable motor and nonmotor features, and myriad overlaps are recognized with other neurodegenerative conditions. Although most commonly characterized by alpha-synuclein protein pathology throughout the central and peripheral nervous systems, the distribution varies and other pathologies commonly modify PD or trigger similar manifestations. Nearly all PD is genetically influenced. More than 100 genes or genetic loci have been identified, and most cases likely arise from interactions among many common and rare genetic variants. Despite its complex architecture, insights from experimental genetic dissection coalesce to reveal unifying biological themes, including synaptic, lysosomal, mitochondrial, andimmune-mediated mechanisms of pathogenesis. This emerging understanding of Parkinson's syndrome, coupled with advances in biomarkers and targeted therapies, presages successful precision medicine strategies.

Structural Cerebellar Abnormalities and Parkinsonism in Patients with 22q11.2 Deletion Syndrome

Background: The phenotypic expression of 22q11.2 deletion syndrome (22q11.2DS) is variable and may include cognitive, psychiatric, and neurological manifestations, e.g., parkinsonism. We investigated brain structural alterations in patients with 22q11.2DS with and without parkinsonism (Park+ and Park-) in comparison with healthy controls (HCs). Methods: Voxel-based morphometry was performed on 3D T1-weighted MR images to explore gray matter volume (GMV) differences between 29 patients (15 Park+, 14 Park-), selected from a consecutive series of 56 adults diagnosed with 22q11.2DS, and 24 HCs. One-way ANOVA and multiple linear regression analyses were performed to explore group differences in GMV and correlations between clinical scores (MDS-UPDR-III and MoCA scores) and structural alterations. Results: Significant between-group differences in GMV were found in the cerebellum, specifically in bilateral lobes VIII and left Crus II, as well as in the left superior occipital gyrus. Although both Park+ and Park- patients showed GMV decrements in these regions with respect to HCs, GMV loss in the right lobe VIII and left Crus II was greater in Park+ than in Park- patients. GMV loss did not correlate with clinical scores. Conclusions: Patients with 22q11.2DS and parkinsonism manifest specific cerebellar volume alterations, supporting the hypothesis of neurodegenerative processes in specific cerebellar regions as a putative pathophysiological mechanism responsible for parkinsonism in patients with 22q11.2DS.

Prevalence and incidence of psychotic disorders in 22q11.2 deletion syndrome: a meta-analysis

22q11.2 deletion syndrome (22q.11.2DS) might be one of the strongest genetic risk factors for psychosis, but robust estimates of prevalence and incidence of psychotic disorders in this condition are not available. To address this gap, we performed a multistep systematic PRISMA/MOOSE-compliant literature search of articles reporting prevalence (primary outcome) or incidence (secondary outcome) of psychotic disorders in 22q11.2DS samples (protocol: https://osf.io/w6hpg) using random-effects meta-analysis, subgroup analyses and meta-regressions. The pooled prevalence of psychotic disorders was 11.50% (95%CI:9.40-14.00%), largely schizophrenia (9.70%, 95%CI:6.50-14.20). Prevalence was significantly higher in samples with a mean age over 18 years, with both psychiatric and non-psychiatric comorbidities and recruited from healthcare services (compared to the community). Mean age was also significantly positively associated with prevalence in meta-regressions (p < 0.01). The pooled incidence of psychotic disorders was 10.60% (95%CI:6.60%-16.70%) at a mean follow-up time of 59.27 ± 40.55 months; meta-regressions were not significant. To our knowledge, this is the first comprehensive systematic review and meta-analysis of the prevalence and incidence of psychotic disorders in 22q11.2DS individuals. It demonstrates that around one in ten individuals with 22q11.2DS displays comorbid psychotic disorders, and around one in ten will develop psychosis in the following five years, indicating that preventive approaches should be implemented systematically in 22q11.2DS.

Parkinsonism in Genetic Neurodevelopmental Disorders: A Systematic Review

Background

With advances in clinical genetic testing, associations between genetic neurodevelopmental disorders and parkinsonism are increasingly recognized. In this review, we aimed to provide a comprehensive overview of reports on parkinsonism in genetic neurodevelopmental disorders and summarize findings related to genetic diagnosis, clinical features and proposed disease mechanisms.

Methods

A systematic literature review was conducted in PubMed and Embase on June 15, 2021. Search terms for parkinsonism and genetic neurodevelopmental disorders, using generic terms and the Human Phenotype Ontology, were combined. Study characteristics and descriptive data were extracted from the articles using a modified version of the Cochrane Consumers and Communication Review Group's data extraction template. The protocol was registered in PROSPERO (CRD42020191035).

Results

The literature search yielded 208 reports for data-extraction, describing 69 genetic disorders in 422 patients. The five most reported from most to least frequent were: 22q11.2 deletion syndrome, beta-propeller protein-associated neurodegeneration, Down syndrome, cerebrotendinous xanthomatosis, and Rett syndrome. Notable findings were an almost equal male to female ratio, an early median age of motor onset (26 years old) and rigidity being more common than rest tremor. Results of dopaminergic imaging and response to antiparkinsonian medication often supported the neurodegenerative nature of parkinsonism. Moreover, neuropathology results showed neuronal loss in the majority of cases. Proposed disease mechanisms included aberrant mitochondrial function and disruptions in neurotransmitter metabolism, endosomal trafficking, and the autophagic-lysosomal and ubiquitin-proteasome system.

Conclusion

Parkinsonism has been reported in many GNDs. Findings from this study may provide clues for further research and improve management of patients with GNDs and/or parkinsonism.

Epigenome-wide association study of human frontal cortex identifies differential methylation in Lewy body pathology

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are closely related progressive disorders with no available disease-modifying therapy, neuropathologically characterized by intraneuronal aggregates of misfolded α-synuclein. To explore the role of DNA methylation changes in PD and DLB pathogenesis, we performed an epigenome-wide association study (EWAS) of 322 postmortem frontal cortex samples and replicated results in an independent set of 200 donors. We report novel differentially methylated replicating loci associated with Braak Lewy body stage near TMCC2, SFMBT2, AKAP6 and PHYHIP. Differentially methylated probes were independent of known PD genetic risk alleles. Meta-analysis provided suggestive evidence for a differentially methylated locus within the chromosomal region affected by the PD-associated 22q11.2 deletion. Our findings elucidate novel disease pathways in PD and DLB and generate hypotheses for future molecular studies of Lewy body pathology.

The potential use of mesenchymal stem cells and their exosomes in Parkinson's disease treatment

Parkinson's disease (PD) is the second most predominant neurodegenerative disease worldwide. It is recognized clinically by severe complications in motor function caused by progressive degeneration of dopaminergic neurons (DAn) and dopamine depletion. As the current standard of treatment is focused on alleviating symptoms through Levodopa, developing neuroprotective techniques is critical for adopting a more pathology-oriented therapeutic approach. Regenerative cell therapy has provided us with an unrivalled platform for evaluating potentially effective novel methods for treating neurodegenerative illnesses over the last two decades. Mesenchymal stem cells (MSCs) are most promising, as they can differentiate into dopaminergic neurons and produce neurotrophic substances. The precise process by which stem cells repair neuronal injury is unknown, and MSC-derived exosomes are suggested to be responsible for a significant portion of such effects. The present review discusses the application of mesenchymal stem cells and MSC-derived exosomes in PD treatment.

Cell line specific alterations in genes associated with dopamine metabolism and signaling in midbrain dopaminergic neurons derived from 22q11.2 deletion carriers with elevated dopamine synthesis capacity

Microdeletions at the 22q11.2 locus are associated with increased risk for schizophrenia. Recent work has demonstrated that antipsychotic naïve 22q11.2 carriers display elevated levels of dopamine synthesis capacity (DSC) as assessed by 18F-DOPA PET imaging. While this is consistent with a role for abnormal dopamine function in schizophrenia, it is unclear what molecular changes may be associated with this neuro-imaging endophenotype, and moreover, if these alterations occur independently of clinical presentation. We therefore conducted a pilot study in which we generated human induced pluripotent stem cells (hiPSCs) from two 22q11.2 deletion carriers with elevated DSC in vivo, but distinct clinical presentations. From these and neurotypical control lines we were able to robustly generate midbrain dopaminergic neurons (mDA-neurons). We then assessed whether genes associated with dopamine synthesis, metabolism or signaling show altered expression between genotypes and further between the 22q11.2 deletion lines. Our data showed alterations in expression of genes associated with dopamine metabolism and signaling that differed between the two 22q11.2 hiPSC lines with distinct clinical presentations. This reinforces the importance of considering clinical, genetic and molecular information, when possible, when choosing which donors to generate hiPSCs from, to carry out mechanistic studies.

Age-Related Improvements in Executive Functions and Focal Attention in 22q11.2 Deletion Syndrome Vary Across Domain and Task

OBJECTIVE

Executive functions (EF) and focal attention have been identified as a weakness in the profile of 22q11.2 deletion syndrome (22q11DS). However, due to a high variety of tasks used across previous studies, it remains unclear whether impairments may be more pronounced for specific subdomains of EF and focal attention. Furthermore, age-related changes have only been examined in a few studies, so far only yielding a partial view of the overall developmental profile.

METHOD

In a broad age range (8-35 years) composed of longitudinal data, 183 participants (103 diagnosed with 22q11DS) completed an extensive assessment of EF and attention. To get a more comprehensive overview of specific versus global impairments, several tasks were assessed within multiple domains.

RESULTS

Results suggest differential impairments and trajectories in specific EF subdomains. Specifically, our findings suggest that individuals with 22q11DS not only showed lower overall inhibition skills, but also that initiation skills developed at a slower pace compared to healthy controls. Results are less clear regarding cognitive flexibility, updating and focal attention, for which performance strongly depended on the tasks that was selected to assess the domain.

CONCLUSIONS

Findings confirm and extend knowledge on differential developmental patterns of EF and attention domains in 22q11DS. They further stress the necessity to administer extensive, multifaceted evaluations to gain a more reliable overview of patients' cognitive profile.

RNA-seq analysis of gene expression profiles in posttraumatic stress disorder, Parkinson's disease and schizophrenia identifies roles for common and distinct biological pathways

Evidence suggests that shared pathophysiological mechanisms in neuropsychiatric disorders (NPDs) may contribute to risk and resilience. We used single-gene and network-level transcriptomic approaches to investigate shared and disorder-specific processes underlying posttraumatic stress disorder (PTSD), Parkinson's disease (PD) and schizophrenia in a South African sample. RNA-seq was performed on blood obtained from cases and controls from each cohort. Gene expression and weighted gene correlation network analyses (WGCNA) were performed using DESeq2 and CEMiTool, respectively. Significant differences in gene expression were limited to the PTSD cohort. However, WGCNA implicated, amongst others, ribosomal expression, inflammation and ubiquitination as key players in the NPDs under investigation. Differential expression in ribosomal-related pathways was observed in the PTSD and PD cohorts, and focal adhesion and extracellular matrix pathways were implicated in PD and schizophrenia. We propose that, despite different phenotypic presentations, core transdiagnostic mechanisms may play important roles in the molecular aetiology of NPDs.

Lewy body disease or diseases with Lewy bodies?

The current nosological concept of α-synucleinopathies characterized by the presence of Lewy bodies (LBs) includes Parkinson’s disease (PD), Parkinson’s disease dementia (PDD), and dementia with Lewy bodies (DLB), for which the term “Lewy body disease” (LBD) has recently been proposed due to their considerable clinical and pathological overlap. However, even this term does not seem to describe the true nature of this group of diseases. The subsequent discoveries of α-synuclein (αSyn), SNCA gene, and the introduction of new immunohistochemical methods have started intensive research into the molecular-biological aspects of these diseases. In light of today’s knowledge, the role of LBs in the pathogenesis and classification of these nosological entities remains somewhat uncertain. An increasingly more important role is attributed to other factors as the presence of various LBs precursors, post-translational αSyn modifications, various αSyn strains, the deposition of other pathological proteins (particularly β-amyloid), and the discovery of selective vulnerability of specific cells due to anatomical configuration or synaptic dysfunction. Resulting genetic inputs can undoubtedly be considered as the main essence of these factors. Molecular–genetic data indicate that not only in PD but also in DLB, a unique genetic architecture can be ascertained, predisposing to the development of specific disease phenotypes. The presence of LBs thus remains only a kind of link between these disorders, and the term “diseases with Lewy bodies” therefore results somewhat more accurate.

Neurogenetic disorders across the lifespan: from aberrant development to degeneration

Intellectual disability and autism spectrum disorder (ASD) are common, and genetic testing is increasingly performed in individuals with these diagnoses to inform prognosis, refine management and provide information about recurrence risk in the family. For neurogenetic conditions associated with intellectual disability and ASD, data on natural history in adults are scarce; however, as older adults with these disorders are identified, it is becoming clear that some conditions are associated with both neurodevelopmental problems and neurodegeneration. Moreover, emerging evidence indicates that some neurogenetic conditions associated primarily with neurodegeneration also affect neurodevelopment. In this Perspective, we discuss examples of diseases that have developmental and degenerative overlap. We propose that neurogenetic disorders should be studied continually across the lifespan to understand the roles of the affected genes in brain development and maintenance, and to inform strategies for treatment.

Effects of copy number variations on brain structure and risk for psychiatric illness: Large-scale studies from the ENIGMA working groups on CNVs

The Enhancing NeuroImaging Genetics through Meta-Analysis copy number variant (ENIGMA-CNV) and 22q11.2 Deletion Syndrome Working Groups (22q-ENIGMA WGs) were created to gain insight into the involvement of genetic factors in human brain development and related cognitive, psychiatric and behavioral manifestations. To that end, the ENIGMA-CNV WG has collated CNV and magnetic resonance imaging (MRI) data from ~49,000 individuals across 38 global research sites, yielding one of the largest studies to date on the effects of CNVs on brain structures in the general population. The 22q-ENIGMA WG includes 12 international research centers that assessed over 533 individuals with a confirmed 22q11.2 deletion syndrome, 40 with 22q11.2 duplications, and 333 typically developing controls, creating the largest-ever 22q11.2 CNV neuroimaging data set. In this review, we outline the ENIGMA infrastructure and procedures for multi-site analysis of CNVs and MRI data. So far, ENIGMA has identified effects of the 22q11.2, 16p11.2 distal, 15q11.2, and 1q21.1 distal CNVs on subcortical and cortical brain structures. Each CNV is associated with differences in cognitive, neurodevelopmental and neuropsychiatric traits, with characteristic patterns of brain structural abnormalities. Evidence of gene-dosage effects on distinct brain regions also emerged, providing further insight into genotype-phenotype relationships. Taken together, these results offer a more comprehensive picture of molecular mechanisms involved in typical and atypical brain development. This "genotype-first" approach also contributes to our understanding of the etiopathogenesis of brain disorders. Finally, we outline future directions to better understand effects of CNVs on brain structure and behavior.

Analysis Of Rem Sleep Without Atonia In 22q11.2 Deletion Syndrome Determined By Domiciliary Polysomnography: A Cross Sectional Study

STUDY OBJECTIVES

Our aim is to evaluate the presence of REM sleep without atonia (RWA), the objective hallmark of REM sleep Behaviour Disorder (RBD), as prodromal marker of Parkinson's disease (PD), in an adult cohort of 22q11.2 deletion syndrome (22qDS).

METHODS

Sleep quality was assessed by means of Pittsburgh quality scale index (PSQI), and RBD symptoms by means of RBD questionnaire-Hong-Kong (RBDQ-HK). Attended domiciliary video-Polysomnography (v-PSG) were performed in 26 adults (18-51 years, 14 females) 22qDS patients. Electromyogram during REM sleep was analyzed by means of SINBAR procedure at 3-second time resolution (miniepochs).

RESULTS

An overall poor sleep quality was observed in the cohort and high RBDQ-HK score in 7 of the 26 patients, two additional patients with positive dream enactment reported by close relatives had low score of RBDQ-HK. Nevertheless, SINBAR RWA scores were lower than cut-off threshold for RWA (mean 5.5%, range 0%-12.2%). TST and the percentage of light sleep (N1) were increased, with preserved proportions of N2 and N3. Participants reported poor quality of sleep (mean PSQI>5), with prolonged sleep latency in the v-PSG. No subjects exhibit evident dream enactment episodes during recording sessions.

CONCLUSIONS

RWA was absent in the studied cohort of 22qDS adult volunteers according to validated polysomnographic criteria. High RBDQ-HK scores do not correlate with v-PSG results among 22qDS individuals.

Functional Dysconnectivity in Ventral Striatocortical Systems in 22q11.2 Deletion Syndrome

22q11.2 deletion syndrome (22q11.2DS) is a genetic neurodevelopmental disorder that represents one of the greatest known risk factors for psychosis. Previous studies in psychotic subjects without the deletion have identified a dopaminergic dysfunction in striatal regions, and dysconnectivity of striatocortical systems, as an important mechanism in the emergence of psychosis. Here, we used resting-state functional MRI to examine striatocortical functional connectivity in 22q11.2DS patients. We used a 2 × 2 factorial design including 125 subjects (55 healthy controls, 28 22q11.2DS patients without a history of psychosis, 10 22q11.2DS patients with a history of psychosis, and 32 subjects with a history of psychosis without the deletion), allowing us to identify network effects related to the deletion and to the presence of psychosis. In line with previous results from psychotic patients without 22q11.2DS, we found that there was a dorsal to ventral gradient of hypo- to hyperstriatocortical connectivity related to psychosis across both patient groups. The 22q11.2DS was additionally associated with abnormal functional connectivity in ventral striatocortical networks, with no significant differences identified in the dorsal system. Abnormalities in the ventral striatocortical system observed in these individuals with high genetic risk to psychosis may thus reflect a marker of illness risk.

Role of COMT V158M Polymorphism in the Development of Dystonia after Administration of Antipsychotic Drugs

Antipsychotics (APDs) represent the main pharmacological strategy in the treatment of schizophrenia; however, their administration often may result in severe adverse effects, such as extrapyramidal symptoms. Typically, dystonic movements are considered the result of impaired function and/or abnormalities of dopaminergic neurotransmission/signaling in the basal ganglia. The catechol O-methyltransferase (COMT) gene is located within the 22q11.2 region, and its product is an enzyme involved in transferring a methyl group from S-adenosylmethionine to catecholamines, including dopamine. Studies showed that COMT Val158Met polymorphism modifies enzymatic activity and, consequently, synaptic dopamine concentration in specific brain areas. We identified a patient with 22q11.2 deletion syndrome presenting with cervical and trunk dystonia after paliperidone administration, which persisted even after drug discontinuation. Given the patient’s genetic condition, we hypothesized that the dopaminergic dysfunction had been aggravated by COMT involvement, thus causing dystonia. In line with this hypothesis, we carried out a study on psychiatric patients in chronic treatment with APD to evaluate the distribution of the COMT Val158Met polymorphism and its role in the onset of adverse extrapyramidal symptoms. The study included four patients with dystonia after administration of APDs compared to 17 patients who never presented adverse drug reactions. Our data suggest that the Val/Val and Met/Met polymorphisms of the COMT gene are associated with a protective effect for the development of collateral extrapyramidal symptoms in patients treated with APDs, while the Val/Met genotype could be considered a risk factor for the development of dystonia after APDs administration.

Novel treatments for autism spectrum disorder based on genomics and systems biology

BACKGROUND

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental disorder with a complex underlying genetic architecture. There are currently no known pharmacologic treatments for the core ASD symptoms of social deficits and restricted/ repetitive behavior. However, there are dozens of clinical trials currently underway that are testing the impact of novel and existing agents on core and associated symptoms in ASD.

METHODS

We present a narrative synthesis of the historical and contemporary challenges to drug discovery in ASD. We then provide an overview of novel treatments currently under investigation from a genomics and systems biology perspective.

RESULTS

Data driven network and cluster analyses suggest alterations in transcriptional regulation, chromatin remodelling, synaptic transmission, neuropeptide signalling, and/or immunological mechanisms may contribute to or underlie the development of ASD. Agents and upcoming trials targeting each of the above listed systems are reviewed.

CONCLUSION

Identifying effective pharmacologic treatments for the core and associated symptom domains in ASD will require further collaboration and innovation in the areas of outcome measurement, biomarker research, and genomics, as well as systematic efforts to identify and treat subgroups of individuals with ASD who may be differentially responsive to specific treatments.

Tremor and Parkinsonism in Chromosomopathies - A Systematic Review

The landscape of genetic forms of Parkinson's diseases (PD) has grown exponentially in recent years. Today, around 10% of PD cases are estimated to be of genetic etiology. However, the link between parkinsonism or tremor and chromosome disorders, both numerical and structural, has been neglected. We reviewed the occurrence and characteristics of parkinsonism and tremor syndromes in patients with chromosomic disorders. We searched PubMed for articles published until December 2018, using the non-MESH terms "Chromosomopathy," "karyotype," "chromosome," "aneuploidy," "deletion," "inversion," "insertion," "duplication," and "Parkinson," "Parkinsonism," "Tremor," and "Parkinsonian disorder." We restricted the search to human studies and selected articles for further analysis after abstract review. Tremor syndromes in which patients had another possible clinical reason for syndromes were excluded, as well as tremor syndromes associated with point mutations, imprinting syndromes, and patients presenting with other hyperkinetic disorders. Fifty-four articles were reviewed. Aneuploidies of sex chromosomes were the most common chromosomopathy. These patients more commonly exhibited postural and kinetic tremor, often meeting the description of essential tremor. In structural chromosomopathies, the most frequent association was PD and 22q11.2 deletion syndrome, but we found case reports and case series of several additional deletion and duplication syndromes. © 2021 International Parkinson and Movement Disorder Society.

Genome-wide Association Analysis of Parkinson's Disease and Schizophrenia Reveals Shared Genetic Architecture and Identifies Novel Risk Loci

BACKGROUND

Parkinson's disease (PD) and schizophrenia (SCZ) are heritable brain disorders that involve dysregulation of the dopaminergic system. Epidemiological studies have reported potential comorbidity between the disorders, and movement disturbances are common in patients with SCZ before treatment with antipsychotic drugs. Despite this, little is known about shared genetic etiology between the disorders.

METHODS

We analyzed recent large genome-wide association studies on patients with SCZ (N = 77,096) and PD (N = 417,508) using a conditional/conjunctional false discovery rate (FDR) approach to evaluate overlap in common genetic variants and improve statistical power for genetic discovery. Using a variety of biological resources, we functionally characterized the identified genomic loci.

RESULTS

We observed genetic enrichment in PD conditional on associations with SCZ and vice versa, indicating polygenic overlap. We then leveraged this cross-trait enrichment using conditional FDR analysis and identified 9 novel PD risk loci and 1 novel SCZ locus at conditional FDR < .01. Furthermore, we identified 9 genomic loci jointly associated with PD and SCZ at conjunctional FDR < .05. There was an even distribution of antagonistic and agonistic effect directions among the shared loci, in line with the insignificant genetic correlation between the disorders. Of 67 genes mapped to the shared loci, 65 are expressed in the human brain and show cell type-specific expression profiles.

CONCLUSIONS

Altogether, the study increases understanding of the genetic architectures underlying SCZ and PD, indicating that common molecular genetic mechanisms may contribute to overlapping pathophysiological and clinical features between the disorders.

Chromosome 22q11.2 deletion causes PERK-dependent vulnerability in dopaminergic neurons

Background

The chromosome 22q11.2 deletion is an extremely high risk genetic factor for various neuropsychiatric disorders; however, the 22q11.2 deletion-related brain pathology in humans at the cellular and molecular levels remains unclear.

Methods

We generated iPS cells from healthy controls (control group) and patients with 22q11.2 deletion (22DS group), and differentiated them into dopaminergic neurons. Semiquantitative proteomic analysis was performed to compare the two groups. Next, we conducted molecular, cell biological and pharmacological assays.

Findings

Semiquantitative proteomic analysis identified ‘protein processing in the endoplasmic reticulum (ER)’ as the most altered pathway in the 22DS group. In particular, we found a severe defect in protein kinase R-like endoplasmic reticulum kinase (PERK) expression and its activity in the 22DS group. The decreased PERK expression was also shown in the midbrain of a 22q11.2 deletion mouse model. The 22DS group showed characteristic phenotypes, including poor tolerance to ER stress, abnormal F-actin dynamics, and decrease in protein synthesis. Some of phenotypes were rescued by the pharmacological manipulation of PERK activity and phenocopied in PERK-deficient dopaminergic neurons. We lastly showed that DGCR14 was associated with reduction in PERK expression.

Interpretation

Our findings led us to conclude that the 22q11.2 deletion causes various vulnerabilities in dopaminergic neurons, dependent on PERK dysfunction.

Funding

This study was supported by the 10.13039/100010463AMED under grant nos JP20dm0107087, JP20dm0207075, JP20ak0101113, JP20dk0307081, and JP18dm0207004h0005; the MEXT KAKENHI under grant nos. 16K19760, 19K08015, 18H04040, and 18K19511; the 10.13039/100008732Uehara Memorial Foundation under grant no. 201810122; and 2019 iPS Academia Japan Grant.

Genetic Risk Profiling in Parkinson's Disease and Utilizing Genetics to Gain Insight into Disease-Related Biological Pathways

Parkinson's disease (PD) is a complex disorder underpinned by both environmental and genetic factors. The latter only began to be understood around two decades ago, but since then great inroads have rapidly been made into deconvoluting the genetic component of PD. In particular, recent large-scale projects such as genome-wide association (GWA) studies have provided insight into the genetic risk factors associated with genetically ''complex'' PD (PD that cannot readily be attributed to single deleterious mutations). Here, we discuss the plethora of genetic information provided by PD GWA studies and how this may be utilized to generate polygenic risk scores (PRS), which may be used in the prediction of risk and trajectory of PD. We also comment on how pathway-specific genetic profiling can be used to gain insight into PD-related biological pathways, and how this may be further utilized to nominate causal PD genes and potentially druggable therapeutic targets. Finally, we outline the current limits of our understanding of PD genetics and the potential contribution of variation currently uncaptured in genetic studies, focusing here on uncatalogued structural variants.

22q11.2 microdeletion and increased risk for type 2 diabetes

BACKGROUND

The 22q11.2 microdeletion is the pathogenic copy number variation (CNV) associated with 22q11.2 deletion syndrome (22q11.2DS, formerly known as DiGeorge syndrome). Familiar endocrinological manifestations include hypoparathyroidism and hypothyroidism, with recent elucidation of elevated risk for obesity in adults. In this study, we aimed to determine whether adults with 22q11.2DS have an increased risk of developing type 2 diabetes (T2D).

METHODS

We studied the effect of the 22q11.2 microdeletion on risk for T2D, defined by history and glycosylated hemoglobin (HbA1c), using weighted survey data from the adult Canadian population (based on n = 11,874) and from a clinical cohort of adults with 22q11.2DS (n = 314), aged 17-69 years. Binomial logistic regression models accounted for age, sex, non-European ethnicity, family history of T2D, obesity, and antipsychotic medication use.

FINDINGS

The 22q11.2 microdeletion was a significant independent risk factor for T2D (OR 2·44, 95% CI 1·39-4·31), accounting for other factors (p < 0·0001). All factors except sex were also significant within 22q11.2DS. The median age at diagnosis of T2D was significantly younger in 22q11.2DS than in the Canadian population sample (32 vs 50 years, p < 0·0001). In adults without T2D, HbA1c was significantly higher in 22q11.2DS than the population (p = 0·042), after accounting for younger age of the 22q11.2DS group.

INTERPRETATION

The results support the 22q11.2 microdeletion as a novel independent risk factor and potential model for early onset T2D. The findings complement emerging evidence that rare CNVs may contribute to risk for T2D. The results have implications for precision medicine and research into the underlying pathogenesis of T2D.

Down regulation of miR-218, miR-124, and miR-144 relates to Parkinson's disease via activating NF-κB signaling

Parkinson's disease (PD) is a neurological degenerative disorder that is partially induced by inflammation in the neural system. To explore the roles of disordered microRNAs in the development of PD, we screened 10 miRNAs in the brain samples of 15 postmortem PD patients and 10 postmortem healthy controls by qRT-PCR. The direct targets of miRNAs were predicted by informatics tools and further confirmed by dual luciferase assay and immunoblotting. The function of miRNAs in regulating NF-κB/p65 translocation was examined by immunoblotting, and the overactivation of NF-κB signaling was examined by ELISA. The relationship between dysregulated miRNAs and cytokines was analyzed by correlation analysis. Three miRNAs were found to be reduced in the brains of patients with PD. KPNB1, KPNA3, and KPNA4 were identified as direct targets of miR-218, miR-124, and miR-144. Additionally, KPNA3 was identified as a direct target of miR-124, and KPNA4 was a direct target of both miR-124 and miR-218. The p65 translocation from the cytoplasm to the nucleus was repressed by miR-124, miR-218, and miR-144 in the SH-SY5Y cells. The NF-κB signaling pathway was overactivated after miRNA inhibitor transfection. The upregulation of KPNB1, KPNA3, and KPNA4 in the brain samples of PD patients was confirmed by immunoblotting, and negative correlations were found between dysregulated miRNAs and cytokines. In conclusion, we identified that the downregulation of miR-218, miR-124, and miR-144 in the brain was related to PD via activation of NF-κB signaling, helping to unveil the role played by dysregulated miRNAs in the pathogenesis of PD and provide new potential targets for PD treatment.

Age-Related Parkinsonian Signs in Microdeletion 22q11.2

Background

The recurrent hemizygous 22q11.2 deletion associated with 22q11.2 deletion syndrome has been identified as a genetic risk factor for early‐onset PD. However, little is known about early motor signs in this condition.

Objectives

We examined the presence, severity and possible factors associated with parkinsonism in adults with 22q11.2 deletion syndrome and without PD.

Methods

We compared motor signs between 82 adults with 22q11.2 deletion syndrome and 25 healthy controls, using the MDS‐UPDRS part III, and three‐dimensional motion‐tracker technology to quantify components of bradykinesia.

Results

Median MDS‐UPDRS part III total and bradykinesia subscores were significantly higher in 22q11.2 deletion syndrome (median age: 26 years; range, 17–65) than in controls (P = 0.000; P = 0.000, respectively). Age was a significant contributor to bradykinesia subscore (B = 0.06; P = 0.01) and to the electronic bradykinesia component, velocity (B = –0.02; P = 0.000); psychotic illness did not significantly impact these analyses. In 22q11.2 deletion syndrome, MDS‐UPDRS–defined bradykinesia was present in 18.3%, rigidity in 14.6%, and rest tremor in 12.2%.

Conclusions

Parkinsonian motor signs appear to be common and age related in 22q11.2 deletion syndrome. Longitudinal studies are needed to investigate possible symptom progression to PD. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Neuronal Autophagy in Synaptic Functions and Psychiatric Disorders

Homeostatic maintenance of physiological functions is fundamental to organismal well-being. Disruption or imbalance in homeostasis results in functional disturbances at molecular, cellular, and tissue levels, leading to manifestation as physical and mental illnesses. Homeostatic imbalance is caused by a range of pathophysiological mechanisms, including disrupted reduction-oxidation reactions, inflammatory responses, metabolic disturbances, or failure in quality control of cellular proteins and organelles. However, the roles for the protein/organelle quality control in the regulation of behaviors, in particular of cognitive processes, had not been well documented, until recent reports finally supported this concept. The frontline studies in neuroscience have revealed that synaptic components (e.g., synaptic proteins, organelles, neurotransmitters and their receptors) are selectively degraded by autophagy, a cellular recycling machinery implicated in surveillance and quality control of proteins and organelles responsible for the maintenance of cellular homeostasis. Apart from the canonical role of autophagy in supporting cell viability, synaptic autophagy appears to regulate synapse remodeling and plasticity. Consistently, emerging evidence suggests novel roles of autophagy in memory encoding, information processing, or cognitive functions. In this review, we overview recent progress in understanding the roles of neuronal autophagy in homeostatic maintenance of synaptic functions, with particular focus on how disruptions in these processes may contribute to the pathophysiology of psychiatric disorders.

miR-185 and SEPT5 Genes May Contribute to Parkinson's Disease Pathophysiology

There are still unknown mechanisms involved in the development of Parkinson's disease (PD), which elucidating them can assist in developing efficient therapies. Recently, studies showed that genes located on the human chromosomal location 22q11.2 might be involved in the development of PD. Therefore, the present study was designed to evaluate the role of two genes located on the chromosomal location (miR-185 and SEPT5), which were the most probable candidates based on our bibliography. In vivo and in vitro models of PD were developed using male Wistar rats and SHSY-5Y cell line, respectively. The expression levels of miR-185, SEPT5, LRRK2, and PARK2 genes were measured at a mRNA level in dopaminergic areas of rats' brains and SHSY-5Y cells using the SYBR Green Real-Time PCR Method. Additionally, the effect of inhibition on the genes or their products on cell viability and gene expression pattern in SHSY-5Y cells was investigated. The level of miR-185 gene expression was significantly decreased in the substantia nigra (SN) and striatum (ST) of the rotenone-treated group (control group) compared to the healthy normal group (P < 0.05). In addition, there was a significant difference in the expression of SEPT5 gene (P < 0.05) in the substantia nigra between two studied groups. The results of an in vitro study showed no significant change in the expression of the genes; however, the inhibition on miR-185 gene expression led to the increase in LRRK2 gene expression in SHSY-5Y cells. The inhibition on LRRK2 protein also decreased the cellular toxicity effect of rotenone on SHSY-5Y cells. The results suggested the protective role of miR-185 gene in preventing the development of PD.

Adverse effects of antipsychotic medication in patients with 22q11.2 deletion syndrome: A systematic review

The 22q11.2 deletion syndrome (22q11.2DS) is a multisystem condition and the most prevalent microdeletion syndrome in humans. Approximately 25% of individuals with 22q11.2DS receive antipsychotic treatment. To assess whether patients with 22q11.2DS are vulnerable to adverse effects of antipsychotic medication, we carried out a literature review. A systematic search strategy was performed using PubMed (Medline), Embase, PsychInfo, and Cochrane Database of Systematic Reviews. Publications describing adverse effects of antipsychotic medication in patients with 22q11.2DS were included in the review and assessed for their methodological quality. A total of 11 publications reporting on eight trials, cross-sectional or cohort studies, and 30 case reports were included. The most commonly reported adverse effects can be classified into the following categories: movement disorders, weight gain, seizures, cardiac side effects, and cytopenias. Many of these symptoms are manifestations of 22q11.2DS, also in the absence of antipsychotic medication. Based on the reviewed literature, a causal relation between antipsychotic medication and the reported adverse effects could not be established in the majority of cases. Randomized clinical trials are needed to make firm conclusions regarding risk of adverse effects of antipsychotics in patients with 22q11.2DS.

Neurobiological perspective of 22q11.2 deletion syndrome

22q11.2 deletion syndrome is characterised by a well defined microdeletion that is associated with a high risk of neuropsychiatric disorders, including intellectual disability, schizophrenia, attention-deficit hyperactivity disorder, autism spectrum disorder, anxiety disorders, seizures and epilepsy, and early-onset Parkinson's disease. Preclinical and clinical data reveal substantial variability of the neuropsychiatric phenotype despite the shared underlying deletion in this genetic model. Factors that might explain this variability include genetic background effects, additional rare pathogenic variants, and potential regulatory functions of some genes in the 22q11.2 deletion region. These factors might also be relevant to the pathophysiology of these neuropsychiatric disorders in the general population. We review studies that might provide insight into pathophysiological mechanisms underlying the expression of neuropsychiatric disorders in 22q11.2 deletion syndrome, and potential implications for these common disorders in the general (non-deleted) population. The recurrent hemizygous 22q11.2 deletion, associated with 22q11.2 deletion syndrome, has attracted attention as a genetic model for common neuropsychiatric disorders because of its association with substantially increased risk of such disorders.¹ Studying such a model has many advantages. First, 22q11.2 deletion has been genetically well characterised.² Second, most genes present in the region typically deleted at the 22q11.2 locus are expressed in the brain.^3-5 Third, genetic diagnosis might be made early in life, long before recognisable neuropsychiatric disorders have emerged. Thus, this genetic condition offers a unique opportunity for early intervention, and monitoring individuals with 22q11.2 deletion syndrome throughout life could provide important information on factors contributing to disease risk and protection. Despite the commonly deleted region being shared by about 90% of individuals with 22q11.2 deletion syndrome, neuropsychiatric outcomes are highly variable between individuals and across the lifespan. A clear link remains to be established between genotype and phenotype.^3,5 In this Review, we summarise preclinical and clinical studies investigating biological mechanisms in 22q11.2 deletion syndrome, with a focus on those that might provide insight into mechanisms underlying neuropsychiatric disorders in 22q11.2 deletion syndrome and in the general population.

Molecular genetics of 22q11.2 deletion syndrome

The 22q11.2 deletion syndrome (22q11.2DS) is a congenital malformation and neuropsychiatric disorder caused by meiotic chromosome rearrangements. One of the goals of this review is to summarize the current state of basic research studies of 22q11.2DS. It highlights efforts to understand the mechanisms responsible for the 22q11.2 deletion that occurs in meiosis. This mechanism involves the four sets of low copy repeats (LCR22) that are dispersed in the 22q11.2 region and the deletion is mediated by nonallelic homologous recombination events. This review also highlights selected genes mapping to the 22q11.2 region that may contribute to the typical clinical findings associated with the disorder and explain that mutations in genes on the remaining allele can uncover rare recessive conditions. Another important aspect of 22q11.2DS is the existence of phenotypic heterogeneity. While some patients are mildly affected, others have severe medical, cognitive, and/or psychiatric challenges. Variability may be due in part to the presence of genetic modifiers. This review discusses current genome-wide efforts to identify such modifiers that could shed light on molecular pathways required for normal human development, cognition or behavior.

All-cause mortality and survival in adults with 22q11.2 deletion syndrome

PURPOSE

Given limited data available on long-term outcomes in 22q11.2 deletion syndrome (22q11.2DS), we investigated mortality risk in adults with this microdeletion syndrome.

METHODS

We studied 309 well-characterized adults (age ≥17 years) with 22q11.2DS and their 1014 unaffected parents and siblings, using a prospective case-control design. We used Cox proportional hazards regression modeling and Kaplan-Meier curves to investigate effects of the 22q11.2 deletion and its associated features on all-cause mortality and survival.

RESULTS

The 22q11.2 deletion (hazard ratio [HR] 8.86, 95% CI 2.87-27.37) and major congenital heart disease (CHD; HR 5.03, 95% CI 2.27-11.17), but not intellectual disability or psychotic illness, were significant independent predictors of mortality for adults with 22q11.2DS compared with their siblings. Amongst those with 22q11.2DS, there were 31 deaths that occurred at a median age of 46.4 (range 18.1-68.6) years; a substantial minority had outlived both parents. Probability of survival to age 45 years was approximately 72% for those with major CHD, and 95% for those with no major CHD (p < 0.0001).

CONCLUSION

For adults with 22q11.2DS, the 22q11.2 deletion and more severe forms of CHD both contribute to a lower life expectancy than family-based expectations. The results have implications for genetic counseling and anticipatory care.

Myoclonic epilepsy, parkinsonism, schizophrenia and left-handedness as common neuropsychiatric features in 22q11.2 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11.2DS) is considered as the genetic model of schizophrenia. However, its polymorphic nature has led researchers to further investigate its neuropsychiatric manifestations.

METHODS

We enrolled 56 adults (38 men, 18 women) diagnosed with 22q11.2DS. All subjects were evaluated by a multidisciplinary team. The neuropsychiatric features were investigated by means of clinical and neurophysiological evaluation (video-EEG).

RESULTS

Thirty per cent of our patients were left-handed. Fifty-eight per cent had a low IQ, and 22 of 56 subjects had psychotic disorders (13 of 22 with schizophrenia). Eighteen patients reported at least one seizure in their lifetime, and ten were diagnosed with epilepsy; among them, seven had genetic generalised epilepsy (GGE), and five of seven showed features suggestive of juvenile myoclonic epilepsy (JME). Video-EEG recordings revealed generalised epileptiform abnormalities in 24 of 56 cases. Besides, only one patient with epilepsy had a cardiac malformation. Lastly, 31 of 56 subjects presented with parkinsonism, 16 of whom were taking neuroleptics. None of the 15 patients with parkinsonism not related to neuroleptic therapy was diagnosed with epilepsy, compared with 6 of those taking antipsychotics.

CONCLUSIONS

22q11.2DS is characterised by left-handedness and neuropsychiatric features such as cognitive impairment, schizophrenia, epilepsy and parkinsonism. GGE, mostly the JME phenotype, is the predominant epilepsy type. The significant association between 22q11.2DS and parkinsonian features confirms these patients' genetic susceptibility to parkinsonism. Despite the lack of any conclusive evidence, our study suggests a possible relationship between the analysed clinical variables: (1) an inverse correlation between low IQ/psychosis/epilepsy and major cardiac diseases; (2) a direct association between psychosis and both mental delay and epilepsy; and (3) an inverse correlation between parkinsonism and epilepsy.

Speech-Language Disorders in 22q11.2 Deletion Syndrome: Best Practices for Diagnosis and Management

Purpose Speech and language disorders are hallmark features of 22q11.2 deletion syndrome (22qDS). Learning disabilities, cognitive deficits, palate abnormalities, velopharyngeal dysfunction, behavioral differences, and various medical and psychiatric conditions are also major features of this syndrome. The goal of this document is to summarize the state of the art of current clinical and scientific knowledge regarding 22qDS for speech-language pathologists (SLPs) and provide recommendations for clinical management. Method Best practices for management of individuals with 22qDS were developed by consensus of an expert international group of SLPs and researchers with expertise in 22qDS. These care recommendations are based on the authors' research, clinical experience, and literature review. Results This document describes the features of 22qDS as well as evaluation procedures, treatment protocols, and associated management recommendations for SLPs for the often complex communication disorders present in this population. Conclusion Early diagnosis and appropriate management of speech-language disorders in 22qDS is essential to optimize outcomes and to minimize the long-term effects of communication impairments. Knowledge of this diagnosis also allows anticipatory care and guidance regarding associated features for families, health care, and educational professionals.

Deep Brain Stimulation in Patients With Mutations in Parkinson's Disease-Related Genes: A Systematic Review

Background

Deep brain stimulation (DBS) is an effective treatment for Parkinson's disease (PD), and careful selection of candidates is a key component of successful therapy. Although it is recognized that factors such as age, disease duration, and levodopa responsiveness can influence outcomes, it is unclear whether genetic background should also serve as a parameter.

Objectives

The aim of this systematic review is to explore studies that have evaluated DBS in patients with mutations in PD-related genes.

Methods

We performed a selective literature search for articles regarding the effects of DBS in autosomal dominant or recessive forms of PD or in PD patients with genetic risk factors. Data regarding changes in motor and nonmotor scores and the presence of adverse events after the stimulation were collected.

Results

A total of 25 studies were included in the systematic review, comprising 135 patients. In the shorter term, most patients showed marked or satisfactory response to subthalamic DBS, although leucine rich repeat kinase 2 carriers of R114G mutations had higher rates of unsatisfactory outcome. Longer term follow-up data were scarce but suggested that motor benefit is sustained. Patients with the glucosidase beta acid (GBA) mutation showed higher rates of cognitive decline after surgery. Motor outcome was scarce for pallidal DBS. Few adverse events were reported.

Conclusions

Subthalamic DBS results in positive outcomes in the short term in patients with Parkin, GBA, and leucine-rich repeat kinase 2 (non-R144G) mutations, although the small sample size limits the interpretation of our findings. Longer and larger cohorts of follow-up, with broader nonmotor symptom evaluations will be necessary to better customize DBS therapy in this population.

Systems Analysis of the 22q11.2 Microdeletion Syndrome Converges on a Mitochondrial Interactome Necessary for Synapse Function and Behavior

Neurodevelopmental disorders offer insight into synaptic mechanisms. To unbiasedly uncover these mechanisms, we studied the 22q11.2 syndrome, a recurrent copy number variant, which is the highest schizophrenia genetic risk factor. We quantified the proteomes of 22q11.2 mutant human fibroblasts from both sexes and mouse brains carrying a 22q11.2-like defect, Df(16)A+/- Molecular ontologies defined mitochondrial compartments and pathways as some of top ranked categories. In particular, we identified perturbations in the SLC25A1-SLC25A4 mitochondrial transporter interactome as associated with the 22q11.2 genetic defect. Expression of SLC25A1-SLC25A4 interactome components was affected in neuronal cells from schizophrenia patients. Furthermore, hemideficiency of the Drosophila SLC25A1 or SLC25A4 orthologues, dSLC25A1-sea and dSLC25A4-sesB, affected synapse morphology, neurotransmission, plasticity, and sleep patterns. Our findings indicate that synapses are sensitive to partial loss of function of mitochondrial solute transporters. We propose that mitoproteomes regulate synapse development and function in normal and pathological conditions in a cell-specific manner.SIGNIFICANCE STATEMENT We address the central question of how to comprehensively define molecular mechanisms of the most prevalent and penetrant microdeletion associated with neurodevelopmental disorders, the 22q11.2 microdeletion syndrome. This complex mutation reduces gene dosage of ∼63 genes in humans. We describe a disruption of the mitoproteome in 22q11.2 patients and brains of a 22q11.2 mouse model. In particular, we identify a network of inner mitochondrial membrane transporters as a hub required for synapse function. Our findings suggest that mitochondrial composition and function modulate the risk of neurodevelopmental disorders, such as schizophrenia.