Clinical Genetics Research Program

Canada

Clinical Genetics Research Program

Canada
SEARCH FILTERS
Time filter
Source Type

Husted J.A.,University of Waterloo | Ahmed R.,University of Waterloo | Chow E.W.C.,Clinical Genetics Research Program | Chow E.W.C.,University of Toronto | And 3 more authors.
Schizophrenia Research | Year: 2010

There is some evidence that childhood adversity may be associated with the expression of schizophrenia but whether genetic risk affects this finding is unknown. We investigated the history of early trauma in 194 subjects from 24 multiply affected families where schizophrenia was previously shown to be associated with a functional allele in the NOS1AP gene. In subjects with schizophrenia (n=79), only events prior to the onset of psychosis were considered. Generalized estimating equation models that adjusted for familial clustering were used to estimate odds ratios (ORs) and 95% confidence intervals (CI). Subjects with narrowly defined schizophrenia were more likely than their unaffected family members to have a history of early trauma (adjusted OR=4.17, 95% CI=1.52, 11.44). The results were similar after adjusting for the NOS1AP risk genotype (adjusted OR=3.57, 95% CI=1.32, 9.65) and for maternal or paternal history of schizophrenia (adjusted ORs=3.27, 95% CI=1.45, 7.38; 4.38, 95% CI=1.61, 11.91, respectively). The results suggest that childhood trauma is associated with expression of schizophrenia independent of measured genetic susceptibility and may be a candidate for gene-environment research using genetic variants. © 2010 Elsevier B.V.


Husted J.A.,University of Waterloo | Ahmed R.,University of Waterloo | Chow E.W.C.,Clinical Genetics Research Program | Chow E.W.C.,University of Toronto | And 3 more authors.
Schizophrenia Research | Year: 2012

There are few studies of environmental factors in familial forms of schizophrenia. We investigated whether childhood adversity or environmental factors were associated with schizophrenia in a familial sample where schizophrenia is associated with the . NOSA1P gene. We found that a cumulative adversity index including childhood illness, family instability and cannabis use was significantly associated with narrow schizophrenia, independent of . NOSA1P risk genotype, previously measured childhood trauma, covariates and familial clustering (adjusted odds ratio (95% confidence interval). =. 1.55 (1.01, 2.38)). The results provide further support that early environmental exposures influence schizophrenia expression even in the presence of strong genetic predisposition. © 2012 Elsevier B.V.


Brzustowicz L.M.,Rutgers University | Bassett A.S.,Clinical Genetics Research Program | Bassett A.S.,University of Toronto
Frontiers in Genetics | Year: 2012

In humans, the most common genomic disorder is a hemizygous deletion of a 1.5-3 Mb region of chromosome 22q11.2. The resultant 22q11.2 deletion syndrome (22q11.2DS) can affect multiple organ systems, and most notably includes cardiac, craniofacial, and neurodevelopmental defects. Individuals with 22q11.2DS have a 20-25-fold risk of developing schizophrenia compared to individuals from the general population, making 22q11.2DS the strongest known molecular genetic risk factor for schizophrenia. Although the deleted region includes DGCR8, a gene coding for a miRNA processing protein, the exact mechanism by which this deletion increases risk is unknown. Importantly, several lines of evidence suggest that miRNAs may modulate risk for schizophrenia in other, non-22q11.2DS populations. Here we present a theory which mechanistically explains the link between 22q11.2DS, miRNAs, and schizophrenia risk. We outline the testable predictions generated by this theory and present preliminary data in support of our model. Further experimental validation of this model could provide important insights into the etiology of both 22q11.2DS and more common forms of schizophrenia. © 2012 Brzustowicz and Bassett.


Costain G.,Clinical Genetics Research Program | Costain G.,University of Toronto | Esplen M.J.,University of Toronto | Toner B.,University of Toronto | And 7 more authors.
Schizophrenia Bulletin | Year: 2014

Background: Recent advances in schizophrenia genetics are shedding new light on etiopathogenesis, but issues germane to translation of findings into clinical practice are relatively understudied. We assessed the need for, and efficacy of, a contemporary genetic counseling protocol for individuals with schizophrenia. Methods: After characterizing rare copy number variation in a cohort of adults with schizophrenia, we recruited subjects from the majority of individuals who had no clinically relevant structural genetic variant. We used a pre-post study design with longitudinal follow-up to assess both the profile of need and the impact of general genetic counseling on key knowledge-based and psychological factors. Results: Thirty-nine (60.0%) of 65 patients approached actively expressed an interest in the study. At baseline, participants (n = 25) tended to overestimate the risk of familial recurrence of schizophrenia, express considerable concern related to this perceived risk, endorse myths about schizophrenia etiology, and blame themselves for their illness. Postcounseling, there was a significant improvement in understanding of the empiric recurrence risk (P =. 0090), accompanied by a decrease in associated concern (P =. 0020). There were also significant gains in subjective (P =. 0007) and objective (P =. 0103) knowledge, and reductions in internalized stigma (P =. 0111) and self-blame (P =. 0401). Satisfaction with genetic counseling, including endorsement of the need for such counseling (86.4%), was high. Conclusions: These results provide initial evidence of need for, and efficacy of, genetic counseling for individuals with schizophrenia. The findings may help facilitate development of a contemporary genetic counseling process that could optimize outcomes in the nascent field of evidence-based psychiatric genetic counseling. © 2012 The Author.


Philip N.,La Timone Childrens Hospital | Bassett A.,Clinical Genetics Research Program | Bassett A.,University of Toronto
Behavior Genetics | Year: 2011

22q11.2 Deletion syndrome has become an important model for understanding the pathophysiology of neurodevelopmental conditions, particularly schizophrenia which develops in about 20-25% of individuals with a chromosome 22q11.2 microdeletion. From the initial discovery of the syndrome, associated developmental delays made it clear that changes in brain development were a key part of the expression. Once patients were followed through childhood into adult years, further neurobehavioural phenotypes became apparent, including a changing cognitive profile, anxiety disorders and seizure diathesis. The variability of expression is as wide as for the myriad physical features associated with the syndrome, with the addition of evolving phenotype over the developmental trajectory. Notably, variability appears unrelated to length of the associated deletion. Several mouse models of the deletion have been engineered and are beginning to reveal potential molecular mechanisms for the cognitive and behavioural phenotypes observable in animals. Both animal and human studies hold great promise for further discoveries relevant to neurodevelopment and associated cognitive, behavioural and psychiatric disorders. © 2011 Springer Science+Business Media, LLC.


Costain G.,Clinical Genetics Research Program | Costain G.,University of Toronto | Esplen M.J.,University of Toronto | Toner B.,University of Toronto | And 4 more authors.
Schizophrenia Bulletin | Year: 2014

Background: Myths and concerns about the extent and meaning of genetic risk in schizophrenia may contribute to significant stigma and burden for families. Genetic counseling has long been proposed to be a potentially informative and therapeutic intervention for schizophrenia. Surprisingly, however, available data are limited. We evaluated a contemporary genetic counseling protocol for use in a community mental health-care setting by non-genetics professionals. Methods: We used a pre-post study design with longitudinal follow-up to assess the impact of genetic counseling on family members of individuals with schizophrenia, where molecular testing had revealed no known clinically relevant genetic risk variant. We assessed the outcome using multiple measures, including standard items and scales used to evaluate genetic counseling for other complex diseases. Results: Of the 122 family members approached, 78 (63.9%) actively expressed an interest in the study. Participants (n = 52) on average overestimated the risk of familial recurrence at baseline, and demonstrated a significant improvement in this estimate postintervention (P <. 0001). This change was associated with an enduring decrease in concern about recurrence (P =. 0003). Significant and lasting benefits were observed in other key areas, including increased knowledge (P <. 0001) and a decreased sense of stigma (P =. 0047). Endorsement of the need for genetic counseling was high (96.1%). Conclusions: These results provide initial evidence of the efficacy of schizophrenia genetic counseling for families, even in the absence of individually relevant genetic test results or professional genetics services. The findings support the integration of contemporary genetic counseling for families into the general management of schizophrenia in the community. © 2012 The Author.


Vorstman J.A.S.,University Utrecht | Breetvelt E.J.,University Utrecht | Thode K.I.,Malcolm Grow Medical Center | Chow E.W.C.,Clinical Genetics Research Program | And 3 more authors.
Schizophrenia Research | Year: 2013

Background: Copy number variants (CNVs) associated with neuropsychiatric disorders are increasingly being identified. While the initial reports were relatively specific, i.e. implicating vulnerability for a particular neuropsychiatric disorder, subsequent studies suggested that most of these CNVs can increase the risk for more than one neuropsychiatric disorder. Possibly, the different neuropsychiatric phenotypes associated with a single genetic variant are really distinct phenomena, indicating pleiotropy. Alternatively, seemingly different disorders could represent the same phenotype observed at different developmental stages or the same underlying pathogenesis with different phenotypic expressions. Aims: To examine the relation between autism and schizophrenia in patients sharing the same CNV. Method: We interviewed parents of 78 adult patients with the 22q11.2 deletion (22q11.2DS) to examine if autistic symptoms during childhood were associated with psychosis in adulthood. We used Chi-square, T-tests and logistic regression while entering cognitive level, gender and age as covariates. Results: The subgroup of 22q11.2DS patients with probable ASD during childhood did not show an increased risk for psychosis in adulthood. The average SRS scores were highly similar between those with and those without schizophrenia. Conclusions: ASD and schizophrenia associated with 22q11.2DS should be regarded as two unrelated, distinct phenotypic manifestations, consistent with true neuropsychiatric pleiotropy. 22q11.2DS can serve as a model to examine the mechanisms associated with neuropsychiatric pleiotropy associated with other CNVs. © 2012 Elsevier B.V.


Butcher N.J.,University of Toronto | Fung W.L.A.,University of Toronto | Fitzpatrick L.,Clinical Genetics Research Program | Guna A.,Clinical Genetics Research Program | And 4 more authors.
British Journal of Psychiatry | Year: 2015

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-ofprinciple for personalised medicine and supports the utility of clinical genetic testing in schizophrenia. © The Royal College of Psychiatrists 2015.


Warnica W.,Clinical Genetics Research Program | Merico D.,Applied Genomics | Costain G.,Clinical Genetics Research Program | Alfred S.E.,Clinical Genetics Research Program | And 5 more authors.
Biological Psychiatry | Year: 2015

Background MicroRNAs (miRNAs) are key regulators of gene expression in the human genome and may contribute to risk for neuropsychiatric disorders. miRNAs play an acknowledged role in the strongest of genetic risk factors for schizophrenia, 22q11.2 deletions. We hypothesized that in schizophrenia there would be an enrichment of other rare copy number variants (CNVs) that overlap miRNAs.Methods Using high-resolution genome-wide microarrays and rigorous methods, we compared the miRNA content of rare CNVs in well-characterized cohorts of schizophrenia cases (n = 420) and comparison subjects, excluding 22q11.2 CNVs. We also performed a gene-set enrichment analysis of the predicted miRNA target genes.Results The schizophrenia group was enriched for the proportion of individuals with a rare CNV overlapping a miRNA (3.29-fold increase over comparison subjects, p <.0001). The presence of a rare CNV overlapping a miRNA remained a significant predictor of schizophrenia case status (p =.0072) in a multivariate logistic regression model correcting for total CNV size. In contrast, comparable analyses correcting for CNV size showed no enrichment of rare CNVs overlapping protein-coding genes. A gene-set enrichment analysis indicated that predicted target genes of recurrent CNV-overlapped miRNAs in schizophrenia may be functionally enriched for neurodevelopmental processes, including axonogenesis and neuron projection development. Predicted gene targets driving these results included CAPRIN1, NEDD4, NTRK2, PAK2, RHOA, and SYNGAP1.Conclusions These data are the first to demonstrate a genome-wide role for CNVs overlapping miRNAs in the genetic risk for schizophrenia. The results provide support for an expanded multihit model of causation, with potential implications for miRNA-based therapeutics.


Costain G.,Clinical Genetics Research Program | Costain G.,University of Toronto | Bassett A.S.,Clinical Genetics Research Program | Bassett A.S.,University of Toronto
Application of Clinical Genetics | Year: 2012

Schizophrenia is a complex neuropsychiatric disease with documented clinical and genetic heterogeneity, and evidence for neurodevelopmental origins. Driven by new genetic technologies and advances in molecular medicine, there has recently been concrete progress in understanding some of the specifc genetic causes of this serious psychiatric illness. In particular, several large rare structural variants have been convincingly associated with schizophrenia, in targeted studies over two decades with respect to 22q11.2 microdeletions, and more recently in large-scale, genome-wide case-control studies. These advances promise to help many families afflicted with this disease. In this review, we critically appraise recent developments in the field of schizophrenia genetics through the lens of immediate clinical applicability. Much work remains in translating the recent surge of genetic research discoveries into the clinic. The epidemiology and basic genetic parameters (such as penetrance and expression) of most genomic disorders associated with schizophrenia are not yet well characterized. To date, 22q11.2 deletion syndrome is the only established genetic subtype of schizophrenia of proven clinical relevance. We use this well-established association as a model to chart the pathway for translating emerging genetic discoveries into clinical practice. We also propose new directions for research involving general genetic risk prediction and counseling in schizophrenia.© 2012 Costain and Bassett, publisher and licensee Dove Medical Press Ltd.

Loading Clinical Genetics Research Program collaborators
Loading Clinical Genetics Research Program collaborators