Altered auditory processing and effective connectivity in 22q11.2 deletion syndrome.

22q11.2 deletion syndrome (22q11.2DS) is one of the most common copy number variants and confers a markedly increased risk for schizophrenia. As such, 22q11.2DS is a homogeneous genetic liability model which enables studies to delineate functional abnormalities that may precede disease onset. Mismatch negativity (MMN), a brain marker of change detection, is reduced in people with schizophrenia compared to healthy controls. Using dynamic causal modelling (DCM), previous studies showed that top-down effective connectivity linking the frontal and temporal cortex is reduced in schizophrenia relative to healthy controls in MMN tasks. In the search for early risk-markers for schizophrenia we investigated the neural basis of change detection in a group with 22q11.2DS. We recorded high-density EEG from 19 young non-psychotic 22q11.2 deletion carriers, as well as from 27 healthy non-carriers with comparable age distribution and sex ratio, while they listened to a sequence of sounds arranged in a roving oddball paradigm. Despite finding no significant reduction in the MMN responses, whole-scalp spatiotemporal analysis of responses to the tones revealed a greater fronto-temporal N1 component in the 22q11.2 deletion carriers. DCM showed reduced intrinsic connection within right primary auditory cortex as well as in the top-down, connection from the right inferior frontal gyrus to right superior temporal gyrus for 22q11.2 deletion carriers although not surviving correction for multiple comparison. We discuss these findings in terms of reduced adaptation and a general increased sensitivity to tones in 22q11.2DS.

Risk of Psychiatric Disorders Among Individuals With the 22q11.2 Deletion or Duplication: A Danish Nationwide, Register-Based Study.

Importance: Microdeletions and duplications have been described at the 22q11.2 locus. However, little is known about the clinical and epidemiologic consequences at the population level. Objective: To identify indicators of deletions or duplications at the 22q11.2 locus and estimate the incidence rate ratios (IRRs) and absolute risk for psychiatric disorders in clinically identified individuals with 22q11.2 deletion or duplication. Design, Setting, and Participants: A Danish nationwide register study including all individuals recorded in the Danish Cytogenetic Central Register with a 22q11.2 deletion or duplication was performed. A total of 3 768 943 individuals born in Denmark from 1955 to 2012 were followed up during the study period (total follow-up, 57.1 million person-years). Indicators of 22q11.2 deletion or duplication and cumulative incidences were estimated using a nested case-control design that included individuals from the population-based cohort. Survival analysis was used to compare risk of disease in individuals with and without the 22q11.2 deletion or duplication. The study was conducted from May 7, 2015, to August 14, 2016. Exposure: The 22q11.2 deletion or duplication. Main Outcomes and Measures: Indicators for carrying a 22q11.2 deletion or duplication, IRR, and cumulative incidences for psychiatric diagnoses (International Statistical Classification of Diseases and Related Health Problems, 10th Revision, codes F00-F99), including schizophrenia-spectrum disorders, mood disorders, neurotic stress-related and somatoform disorders, and a range of developmental and childhood disorders. Results: Among the 3 768 943 participants, 244 (124 [50.8%] male) and 58 (29 [50.0%] male) individuals were clinically identified with a 22q11.2 deletion or duplication, respectively. Mean (SD) age at diagnosis of any psychiatric disorder was 12.5 (8.3) years for individuals with deletions and 6.1 (0.9) years for duplication carriers. A parental diagnosis of schizophrenia-but not of other psychiatric diagnoses-was associated with a 22q11.2 deletion, and parental psychiatric diagnoses other than schizophrenia were associated with duplication carrier status. Both the 22q11.2 deletion (IRR, 4.24; 95% CI, 3.07-5.67) and duplication (IRR, 4.99; 95% CI, 1.79-10.72) was associated with increased risk of any psychiatric disorders. Furthermore, a highly increased risk of intellectual disability was found for the deletion (IRR, 34.08; 95% CI, 22.39-49.27) and duplication (IRR, 33.86; 95% CI, 8.42-87.87). Furthermore, individuals with the 22q11.2 deletion had an increased risk of several psychiatric disorders under study, for example, pervasive developmental disorders (IRR, 9.45; 95% CI, 5.64-14.69) and childhood autism (IRR, 8.94; 95% CI, 3.21-19.23). Conclusions and Relevance: Individuals with the 22q11.2 deletion or duplication have a significantly increased risk of developing psychiatric disorders. Survival analysis of persons carrying either the 22q11.2 deletion or duplication provides estimates of direct clinical relevance useful to assist clinical ascertainment, genetic counseling, guidance of symptomatic monitoring, and early clinical intervention.

Schizophrenia Spectrum Disorders in a Danish 22q11.2 Deletion Syndrome Cohort Compared to the Total Danish Population--A Nationwide Register Study.

OBJECTIVE: Cross-sectional studies have shown associations between 22q11.2 deletion syndrome and schizophrenia. However, large-scale prospective studies have been lacking. We, therefore, conducted the first large-scale population based study on the risk of being diagnosed with schizophrenia in persons identified with 22q11.2 deletion syndrome. METHODS: Danish nationwide registers were linked to establish a cohort consisting of all Danish citizens born during 1955-2004 and the cohort was followed from January 1, 1994 until December 31, 2013. Data were analyzed using survival analyses and adjusted for calendar year, age, sex, and parental mental health history. RESULTS: A total of 156 individuals with 22q11.2 deletion syndrome were identified, out of which 6 individuals were diagnosed with schizophrenia spectrum disorders following identification with 22q11 deletion syndrome. Identified carriers of 22q11.2 deletion had an 8.13(95% CI: 3.65-18.09) fold increased risk of schizophrenia spectrum disorder. CONCLUSIONS: Carriers of a 22q11.2 deletion who had been clinically identified had a highly increased risk of schizophrenia spectrum disorders.

The Danish 22q11 research initiative.

BACKGROUND: Neurodevelopmental brain disorders such as schizophrenia, autism and attention deficit hyperactivity disorder are complex disorders with heterogeneous etiologies. Schizophrenia and autism are difficult to treat and often cause major individual suffering largely owing to our limited understanding of the disease biology. Thus our understanding of the biological pathogenesis needs to be substantiated to enable development of more targeted treatment options with improved efficacy. Insights into the pre-morbid disease dynamics, the morbid condition and the underlying biological disease mechanisms may come from studies of subjects with homogenous etiologies. Breakthroughs in psychiatric genetics have shown that several genetic anomalies predispose for neurodevelopmental brain disorders. We have established a Danish research initiative to study the common microdeletion at chromosome 22q11.2, which is one of the genetic anomalies that confer high risk of schizophrenia, autism and attention deficit hyperactivity disorder. METHODS/DESIGN: The study applies a "cause-to-outcome" strategy to identify pre-morbid pathogenesis and underlying biological disease mechanisms of psychosis and secondarily the morbid condition of autism and attention deficit hyperactivity disorder. We use a population based epidemiological design to inform on disease prevalence, environmental risk factors and familial disposition for mental health disorders and a case control study design to map the functional effects across behavioral and neurophysiological traits of the 22q11 deletion in a recruited sample of Danish individuals. DISCUSSION: Identification of predictive pre-morbid clinical, cognitive, functional and structural brain alterations in 22q11 deletion carriers may alter current clinical practice from symptomatic therapy of manifest mental illness into early intervention strategies, which may also be applicable to at risk subjects without known etiology. Hopefully new insights into the biological disease mechanisms, which are mandatory for novel drug developments, can improve the outcome of the pharmacological interventions in psychiatry.

Enhanced maternal origin of the 22q11.2 deletion in velocardiofacial and DiGeorge syndromes.

Velocardiofacial and DiGeorge syndromes, also known as 22q11.2 deletion syndrome (22q11DS), are congenital-anomaly disorders caused by a de novo hemizygous 22q11.2 deletion mediated by meiotic nonallelic homologous recombination events between low-copy repeats, also known as segmental duplications. Although previous studies exist, each was of small size, and it remains to be determined whether there are parent-of-origin biases for the de novo 22q11.2 deletion. To address this question, we genotyped a total of 389 DNA samples from 22q11DS-affected families. A total of 219 (56%) individuals with 22q11DS had maternal origin and 170 (44%) had paternal origin of the de novo deletion, which represents a statistically significant bias for maternal origin (p = 0.0151). Combined with many smaller, previous studies, 465 (57%) individuals had maternal origin and 345 (43%) had paternal origin, amounting to a ratio of 1.35 or a 35% increase in maternal compared to paternal origin (p = 0.000028). Among 1,892 probands with the de novo 22q11.2 deletion, the average maternal age at time of conception was 29.5, and this is similar to data for the general population in individual countries. Of interest, the female recombination rate in the 22q11.2 region was about 1.6-1.7 times greater than that for males, suggesting that for this region in the genome, enhanced meiotic recombination rates, as well as other as-of-yet undefined 22q11.2-specific features, could be responsible for the observed excess in maternal origin.