Nancy J. Butcher

Cognitive Decline Preceding the Onset of Psychosis in Patients With 22q11.2 Deletion Syndrome

IMPORTANCE Patients with 22q11.2 deletion syndrome (22q11DS) have an elevated (25%) risk of developing schizophrenia. Recent reports have suggested that a subgroup of children with 22q11DS display a substantial decline in cognitive abilities starting at a young age. OBJECTIVE To determine whether early cognitive decline is associated with risk of psychotic disorder in 22q11DS. DESIGN, SETTING, AND PARTICIPANTS Prospective longitudinal cohort study. As part of an international research consortium initiative, we used the largest data set of intelligence (IQ) measurements in patients with 22q11DS reported to date to investigate longitudinal IQ trajectories and the risk of subsequent psychotic illness. A total of 829 patients with a confirmed hemizygous 22q11.2 deletion, recruited through 12 international clinical research sites, were included. Both psychiatric assessments and longitudinal IQ measurements were available for a subset of 411 patients (388 with ≥1 assessment at age 8-24 years). MAIN OUTCOMES AND MEASURES Diagnosis of a psychotic disorder, initial IQ, longitudinal IQ trajectory, and timing of the last psychiatric assessment with respect to the last IQ test. RESULTS Among 411 patients with 22q11DS, 55 (13.4%) were diagnosed as having a psychotic disorder. The mean (SD) age at the most recent psychiatric assessment was 16.1 (6.2) years. The mean (SD) full-scale IQ at first cognitive assessment was lower in patients who developed a psychotic disorder (65.5 [12.0]) compared with those without a psychotic disorder (74.0 [14.0]). On average, children with 22q11DS showed a mild decline in IQ (full-scale IQ, 7.04 points) with increasing age, particularly in the domain of verbal IQ (9.02 points). In those who developed psychotic illness, this decline was significantly steeper (P < .001). Those with a negative deviation from the average cognitive trajectory observed in 22q11DS were at significantly increased risk for the development of a psychotic disorder (odds ratio = 2.49; 95% CI, 1.24-5.00; P = .01). The divergence of verbal IQ trajectories between those who subsequently developed a psychotic disorder and those who did not was distinguishable from age 11 years onward. CONCLUSIONS AND RELEVANCE In 22q11DS, early cognitive decline is a robust indicator of the risk of developing a psychotic illness. These findings mirror those observed in idiopathic schizophrenia. The results provide further support for investigations of 22q11DS as a genetic model for elucidating neurobiological mechanisms underlying the development of psychosis.

Practical guidelines for managing adults with 22q11.2 deletion syndrome

22q11.2 Deletion syndrome (22q11.2DS) is the most common microdeletion syndrome in humans, estimated to affect up to 1 in 2,000 live births. Major features of this multisystem condition include congenital anomalies, developmental delay, and an array of early- and later-onset medical and psychiatric disorders. Advances in pediatric care ensure a growing population of adults with 22q11.2DS. Informed by an international panel of multidisciplinary experts and a comprehensive review of the existing literature concerning adults, we present the first set of guidelines focused on managing the neuropsychiatric, endocrine, cardiovascular, reproductive, psychosocial, genetic counseling, and other issues that are the focus of attention in adults with 22q11.2DS. We propose practical strategies for the recognition, evaluation, surveillance, and management of the associated morbidities.Genet Med 17 8, 599–609.

Association Between Early-Onset Parkinson Disease and 22q11.2 Deletion Syndrome: Identification of a Novel Genetic Form of Parkinson Disease and Its Clinical Implications

IMPORTANCE Clinical case reports of parkinsonism co-occurring with hemizygous 22q11.2 deletions and the associated multisystem syndrome, 22q11.2 deletion syndrome (22q11.2DS), suggest that 22q11.2 deletions may lead to increased risk of early-onset Parkinson disease (PD). The frequency of PD and its neuropathological presentation remain unknown in this common genetic condition. OBJECTIVE To evaluate a possible association between 22q11.2 deletions and PD. DESIGN, SETTING, AND PARTICIPANTS An observational study of the occurrence of PD in the worlds largest cohort of well-characterized adults with a molecularly confirmed diagnosis of 22q11.2DS (n = 159 [6 with postmortem tissue]; age range, 18.1-68.6 years) was conducted in Toronto, Ontario, Canada. Rare postmortem brain tissue from individuals with 22q11.2DS and a clinical history of PD was investigated for neurodegenerative changes and compared with that from individuals with no history of a movement disorder. MAIN OUTCOMES AND MEASURES A clinical diagnosis of PD made by a neurologist and neuropathological features of PD. RESULTS Adults with 22q11.2DS had a significantly elevated occurrence of PD compared with standard population estimates (standardized morbidity ratio = 69.7; 95% CI, 19.0-178.5). All cases showed early onset and typical PD symptom pattern, treatment response, and course. All were negative for family history of PD and known pathogenic PD-related mutations. The common use of antipsychotics in patients with 22q11.2DS to manage associated psychiatric symptoms delayed diagnosis of PD by up to 10 years. Postmortem brain tissue revealed classic loss of midbrain dopaminergic neurons in all 3 postmortem 22q11.2DS-PD cases. Typical α-synuclein-positive Lewy bodies were present in the expected distribution in 2 cases but absent in another. CONCLUSIONS AND RELEVANCE These findings suggest that 22q11.2 deletions represent a novel genetic risk factor for early-onset PD with variable neuropathological presentation reminiscent of LRRK2-associated PD neuropathology. Individuals with early-onset PD and classic features of 22q11.2DS should be considered for genetic testing, and those with a known 22q11.2 deletion should be monitored for the development of parkinsonian symptoms. Molecular studies of the implicated genes, including DGCR8, may help shed light on the underlying pathophysiology of PD in 22q11.2DS and idiopathic PD.

Functional outcomes of adults with 22q11.2 deletion syndrome

Purpose:The 22q11.2 deletion syndrome is a common multisystem genomic disorder with congenital and later-onset manifestations, including congenital heart disease, intellectual disability, and psychiatric illness, that may affect long-term functioning. There are limited data on adult functioning in 22q11.2 deletion syndrome.Methods:We used the Vineland Adaptive Behavior Scales to assess functioning in 100 adults with 22q11.2 deletion syndrome (n = 46 male; mean age = 28.8 (standard deviation = 9.7) years) where intellect ranged from average to borderline (n = 57) to mild intellectual disability (n = 43).Results:More than 75% of the subjects scored in the functional deficit range. Although personal, vocational, and financial demographics confirmed widespread functional impairment, daily living skills and employment were relative strengths. Intelligence quotient was a significant predictor (P < 0.001) of overall and domain-specific adaptive functioning skills. A diagnosis of schizophrenia was a significant predictor (P < 0.05) of overall adaptive functioning, daily living skills, and socialization scores. Notably, congenital heart disease, history of mood/anxiety disorders, sex, and age were not significant predictors of functioning.Conclusion:Despite functional impairment in adulthood that is primarily mediated by cognitive and psychiatric phenotypes, relative strengths in activities of daily living and employment have important implications for services and long-term planning. These results may help to inform expectations about outcomes for patients with 22q11.2 deletion syndrome.Genet Med 2012:14(10):836–843

Response to clozapine in a clinically identifiable subtype of schizophrenia.

BACKGROUND Genetic testing in psychiatry promises to improve patient care through advances in personalised medicine. However, there are few clinically relevant examples. AIMS To determine whether patients with a well-established genetic subtype of schizophrenia show a different response profile to the antipsychotic clozapine than those with idiopathic schizophrenia. METHOD We retrospectively studied the long-term safety and efficacy of clozapine in 40 adults with schizophrenia, half with a 22q11.2 deletion (22q11.2DS group) and half matched for age and clinical severity but molecularly confirmed to have no pathogenic copy number variant (idiopathic group). RESULTS Both groups showed similar clinical improvement and significant reductions in hospitalisations, achieved at a lower median dose for those in the 22q11.2DS group. Most common side-effects were similarly prevalent between the two groups, however, half of the 22q11.2DS group experienced at least one rare serious adverse event compared with none of the idiopathic group. Many were successfully retried on clozapine. CONCLUSIONS Individuals with 22q11.2DS-schizophrenia respond as well to clozapine treatment as those with other forms of schizophrenia, but may represent a disproportionate number of those with serious adverse events, primarily seizures. Lower doses and prophylactic (for example anticonvulsant) management strategies can help ameliorate side-effect risks. This first systematic evaluation of antipsychotic response in a genetic subtype of schizophrenia provides a proof-of-principle for personalised medicine and supports the utility of clinical genetic testing in schizophrenia.

Comparative mapping of the 22q11.2 deletion region and the potential of simple model organisms

Background22q11.2 deletion syndrome (22q11.2DS) is the most common micro-deletion syndrome. The associated 22q11.2 deletion conveys the strongest known molecular risk for schizophrenia. Neurodevelopmental phenotypes, including intellectual disability, are also prominent though variable in severity. Other developmental features include congenital cardiac and craniofacial anomalies. Whereas existing mouse models have been helpful in determining the role of some genes overlapped by the hemizygous 22q11.2 deletion in phenotypic expression, much remains unknown. Simple model organisms remain largely unexploited in exploring these genotype-phenotype relationships.MethodsWe first developed a comprehensive map of the human 22q11.2 deletion region, delineating gene content, and brain expression. To identify putative orthologs, standard methods were used to interrogate the proteomes of the zebrafish (D. rerio), fruit fly (D. melanogaster), and worm (C. elegans), in addition to the mouse. Spatial locations of conserved homologues were mapped to examine syntenic relationships. We systematically cataloged available knockout and knockdown models of all conserved genes across these organisms, including a comprehensive review of associated phenotypes.ResultsThere are 90 genes overlapped by the typical 2.5 Mb deletion 22q11.2 region. Of the 46 protein-coding genes, 41 (89.1 %) have documented expression in the human brain. Identified homologues in the zebrafish (n = 37, 80.4 %) were comparable to those in the mouse (n = 40, 86.9 %) and included some conserved gene cluster structures. There were 22 (47.8 %) putative homologues in the fruit fly and 17 (37.0 %) in the worm involving multiple chromosomes. Individual gene knockdown mutants were available for the simple model organisms, but not for mouse. Although phenotypic data were relatively limited for knockout and knockdown models of the 17 genes conserved across all species, there was some evidence for roles in neurodevelopmental phenotypes, including four of the six mitochondrial genes in the 22q11.2 deletion region.ConclusionsSimple model organisms represent a powerful but underutilized means of investigating the molecular mechanisms underlying the elevated risk for neurodevelopmental disorders in 22q11.2DS. This comparative multi-species study provides novel resources and support for the potential utility of non-mouse models in expression studies and high-throughput drug screening. The approach has implications for other recurrent copy number variations associated with neurodevelopmental phenotypes.

Whole-Genome Sequencing Suggests Schizophrenia Risk Mechanisms in Humans with 22q11.2 Deletion Syndrome

Chromosome 22q11.2 microdeletions impart a high but incomplete risk for schizophrenia. Possible mechanisms include genome-wide effects of DGCR8 haploinsufficiency. In a proof-of-principle study to assess the power of this model, we used high-quality, whole-genome sequencing of nine individuals with 22q11.2 deletions and extreme phenotypes (schizophrenia, or no psychotic disorder at age >50 years). The schizophrenia group had a greater burden of rare, damaging variants impacting protein-coding neurofunctional genes, including genes involved in neuron projection (nominal P = 0.02, joint burden of three variant types). Variants in the intact 22q11.2 region were not major contributors. Restricting to genes affected by a DGCR8 mechanism tended to amplify between-group differences. Damaging variants in highly conserved long intergenic noncoding RNA genes also were enriched in the schizophrenia group (nominal P = 0.04). The findings support the 22q11.2 deletion model as a threshold-lowering first hit for schizophrenia risk. If applied to a larger and thus better-powered cohort, this appears to be a promising approach to identify genome-wide rare variants in coding and noncoding sequence that perturb gene networks relevant to idiopathic schizophrenia. Similarly designed studies exploiting genetic models may prove useful to help delineate the genetic architecture of other complex phenotypes.

MicroRNA Dysregulation, Gene Networks, and Risk for Schizophrenia in 22q11.2 Deletion Syndrome.

The role of microRNAs (miRNAs) in the etiology of schizophrenia is increasingly recognized. Microdeletions at chromosome 22q11.2 are recurrent structural variants that impart a high risk for schizophrenia and are found in up to 1% of all patients with schizophrenia. The 22q11.2 deletion region overlaps gene DGCR8, encoding a subunit of the miRNA microprocessor complex. We identified miRNAs overlapped by the 22q11.2 microdeletion and for the first time investigated their predicted target genes, and those implicated by DGCR8, to identify targets that may be involved in the risk for schizophrenia. The 22q11.2 region encompasses seven validated or putative miRNA genes. Employing two standard prediction tools, we generated sets of predicted target genes. Functional enrichment profiles of the 22q11.2 region miRNA target genes suggested a role in neuronal processes and broader developmental pathways. We then constructed a protein interaction network of schizophrenia candidate genes and interaction partners relevant to brain function, independent of the 22q11.2 region miRNA mechanisms. We found that the predicted gene targets of the 22q11.2 deletion miRNAs, and targets of the genome-wide miRNAs predicted to be dysregulated by DGCR8 hemizygosity, were significantly represented in this schizophrenia network. The findings provide new insights into the pathway from 22q11.2 deletion to expression of schizophrenia, and suggest that hemizygosity of the 22q11.2 region may have downstream effects implicating genes elsewhere in the genome that are relevant to the general schizophrenia population. These data also provide further support for the notion that robust genetic findings in schizophrenia may converge on a reasonable number of final pathways.

Movement Disorders and Other Motor Abnormalities in Adults With 22q11.2 Deletion Syndrome

Movement abnormalities are frequently reported in children with 22q11.2 deletion syndrome (22q11.2DS), but knowledge in this area is scarce in the increasing adult population. We report on five individuals illustrative of movement disorders and other motor abnormalities in adults with 22q11.2DS. In addition to an increased susceptibility to neuropsychiatric disorders, seizures, and early‐onset Parkinson disease, the underlying brain dysfunction associated with 22q11.2DS may give rise to an increased vulnerability to multiple movement abnormalities, including those influenced by medications. Movement abnormalities may also be secondary to treatable endocrine diseases and congenital musculoskeletal abnormalities. We propose that movement abnormalities may be common in adults with 22q11.2DS and discuss the implications and challenges important to clinical practice.

Fetal growth and gestational factors as predictors of schizophrenia in 22q11.2 deletion syndrome

Purpose:Schizophrenia occurs in 20–25% of adults with 22q11.2 deletion syndrome (22q11.2DS). General population studies of schizophrenia report associations with perinatal complications, although effect sizes are generally low. We aimed to determine whether such factors are associated with expression of schizophrenia in individuals with 22q11.2DS.Methods:We investigated the relationship of small for gestational age (SGA) birth weight (<3rd percentile for sex and gestational age) and prematurity (<37 weeks gestation) to expression of schizophrenia in a well-characterized cohort of 123 adults with 22q11.2DS. Outcome measures included adjusted odds ratios and positive and negative predictive values (PPV and NPV) for schizophrenia.Results:SGA birth weight (OR = 3.52, 95% CI = 1.34–9.22) and prematurity (OR = 5.38, 95% CI = 1.63–17.75), but not maternal factors, were significant risk factors for schizophrenia in 22q11.2DS. Being born SGA or premature resulted in a PPV of 46% for schizophrenia; NPV in the absence of both features was 83%. Post hoc analyses suggested these perinatal complications were also associated with factors indicative of increased severity of schizophrenia.Conclusion:In 22q11.2DS, fetal growth and gestation may have a clinically significant impact on future risk for schizophrenia. These data advance our understanding of determinants of disease-specific expression in 22q11.2DS, with implications for other genomic disorders.Genet Med 18 4, 350–355.