A review of neurocognitive and behavioral profiles associated with 22q11 deletion syndrome: implications for clinical evaluation and treatment

Mental health, coping, and protective factors in mothers of children with 22q11.2 deletion syndrome

Compared to the large body of maternal mental health research for other pediatric disorders, we know far less about the experience of mothers of children with 22q11DS. This study investigates the coping methods, protective factors, and mental health of this population. These findings might lead to better support for 22q11DS maternal mental health. An international sample of 71 mothers (M = 40.5 years) of children with 22q11DS (M = 9.2 years) was recruited and completed an online survey assessing maternal mental health (symptoms of depression, anxiety, traumatic stress, general stress, and alcohol consumption), coping methods, and mental health protective factors (social support, dyadic adjustment, parenting competence). Maternal ratings of child mental health symptoms were also obtained. Mothers' self-report revealed a high percentage who screened positive for elevated levels of general stress (69%), hazardous alcohol consumption (30.9%), traumatic stress (33.8%), anxiety (26.8%), and depression (26.8%). After controlling for demographic variables and child mental health symptoms, maternal self-reported maladaptive coping methods were positively associated with maternal symptoms of depression, anxiety, stress, and traumatic stress. Reducing maladaptive coping methods may be a promising intervention for improving mental health in mothers of children with 22q11DS.

Evaluation and Maintenance of Behavioral Interventions for 22q11.2 Deletion Syndrome

22q11.2-deletion syndrome is a genetic disorder caused by a small deletion of chromosome 22. This deletion often results in developmental delays, learning disabilities, medical conditions, and comorbid psychiatric conditions. Patients with 22q11.2DS may present with a variety of behavioral phenotypes including obsessiveness and rigidity, poor social skills, and anxiety. In some cases, the phenotype can consist of destructive and inappropriate behavior including harming self and others. Behavioral difficulties are reported as one of the most challenging aspects of 22q11.2-deletion syndrome for families of patients, however, few studies have examined behavioral interventions as a possible therapeutic treatment for this population. Using principles derived from operant-behavioral psychology, we conducted functional assessments to determine the environmental correlates of destructive and inappropriate behaviors in two adult men with 22q11.2-deletion syndrome. Subsequently, behavioral interventions based on differential reinforcement were incorporated into each participant's natural environment to eliminate these behaviors. Significant reductions in destructive and inappropriate behavior were observed with both participants and therapeutic gains were maintained at follow-up. We discuss the role of behavioral interventions in combination with appropriate psychotropic medication when addressing challenging behaviors in this population.

OUP accepted manuscript

Multiple pieces of evidence support the prenatal predisposition of autism spectrum disorder (ASD). Nevertheless, robust data about abnormalities in foetuses later developing into children diagnosed with ASD are lacking. Prenatal ultrasound is an excellent tool to study abnormal foetal development as it is frequently used to monitor foetal growth and identify foetal anomalies throughout pregnancy. We conducted a retrospective case-sibling-control study of children diagnosed with ASD (cases); their own typically developing, closest-in-age siblings (TDS); and typically developing children from the general population (TDP), matched by year of birth, sex and ethnicity to investigate the association between ultrasonography foetal anomalies and ASD. The case group was drawn from all children diagnosed with ASD enrolled at the National Autism Research Center of Israel. Foetal ultrasound data from the foetal anatomy survey were obtained from prenatal ultrasound clinics of Clalit Health Services in southern Israel. The study comprised 659 children: 229 ASD, 201 TDS and 229 TDP. Ultrasonography foetal anomalies were found in 29.3% of ASD cases versus only 15.9% and 9.6% in the TDS and TDP groups [adjusted odds ratio (aOR) = 2.23, 95% confidence interval (CI) = 1.32-3.78, and aOR = 3.50, 95%CI = 2.07-5.91, respectively]. Multiple co-occurring ultrasonography foetal anomalies were significantly more prevalent among ASD cases. Ultrasonography foetal anomalies in the urinary system, heart, and head and brain were the most significantly associated with ASD diagnosis (aORUrinary = 2.08, 95%CI = 0.96-4.50 and aORUrinary = 2.90, 95%CI = 1.41-5.95; aORHeart = 3.72, 95%CI = 1.50-9.24 and aORHeart = 8.67, 95%CI = 2.62-28.63; and aORHead&Brain = 1.96, 95%CI = 0.72-5.30 and aORHead&Brain = 4.67, 95%CI = 1.34-16.24; versus TDS and TDP, respectively). ASD females had significantly more ultrasonography foetal anomalies than ASD males (43.1% versus 25.3%, P = 0.013) and a higher prevalence of multiple co-occurring ultrasonography foetal anomalies (15.7% versus 4.5%, P = 0.011). No sex differences were seen among TDS and TDP controls. ASD foetuses were characterized by a narrower head and a relatively wider ocular-distance versus TDP foetuses (ORBPD = 0.81, 95%CI = 0.70-0.94, and aOROcular distance = 1.29, 95%CI = 1.06-1.57). Ultrasonography foetal anomalies were associated with more severe ASD symptoms. Our findings shed important light on the multiorgan foetal anomalies associated with ASD.

Anhedonia and Hyperhedonia in Autism and Related Neurodevelopmental Disorders

Although autism spectrum disorder (ASD) is defined by impaired social communication and restricted and repetitive behaviors and interests, ASD is also characterized by impaired motivational processes. The "social motivation theory of autism" describes how social motivation disruptions in ASD in early childhood may impede the drive to engage in reciprocal social behaviors and ultimately interfere with the development of neural networks critical for social communication (Chevallier et al., Trends Cogn Sci 16:231-239, 2012b). Importantly, clinical studies and preclinical research using model organisms for ASD indicate that motivational impairments in ASD are not constrained to social rewards but are evident in response to a range of nonsocial rewards as well. Additionally, translational studies on certain genetically defined neurodevelopmental disorders associated with ASD indicate that these syndromic forms of ASD are also characterized by motivational deficits and mesolimbic dopamine impairments. In this chapter we summarize clinical and preclinical research relevant to reward processing impairments in ASD and related neurodevelopmental disorders. We also propose a nosology to describe reward processing impairments in these disorders that uses a three-axes model. In this triaxial nosology, the first axis defines the direction of the reward response (i.e., anhedonic, hyperhedonic); the second axis defines the construct of the reward process (e.g., reward liking, reward wanting); and the third axis defines the context of the reward response (e.g., social, nonsocial). A more precise nosology for describing reward processing impairments in ASD and related neurodevelopmental disorders will aid in the translation of preclinical research to clinical investigations which will ultimately help to speed up the development of interventions that target motivational systems for ASD and related neurodevelopmental disorders.

Cross-sectional and longitudinal findings in patients with proximal 22q11.2 duplication: A retrospective chart study

Duplications on Chromosome 22q11.2 (22q11.2 dup) are associated with a wide spectrum of physical and neurodevelopmental features. In this chart review, physical, developmental, and behavioral features of 28 patients with 22q11.2 dup (median age = 17.11 years) are reported, and phenotypes of de novo and inherited duplications are compared. Common medical anomalies include nutritional problems (57%), failure to thrive (33%), transient hearing impairment (52%), and congenital heart defects (33%). Developmental, speech-language, and motor delay are common in infancy, while attention (64%), learning (60%), and motor problems (52%) are typically reported at primary school age. Attention-deficit/hyperactivity disorders are diagnosed in 44%. Median full-scale intelligence quotient is in the borderline range (IQ 76), with one-fifth of patients having mild intellectual disability. Longitudinal data in 11 patients, with the first assessment at a median age of 5.2 years and the second assessment at a median age of 8.8 years, indicate that almost two-third of patients have a relative stable cognitive trajectory, whereas one-third show a growing into deficit profile. In patients with de novo duplications, there is a trend of more failure to thrive, while more patients with inherited duplications follow special education.

Neuropsychological and ASD phenotypes in rare genetic syndromes: A critical review of the literature

OBJECTIVE

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by core deficits in social communication and restricted and repetitive behaviors and interests. Recent advances in clinical genetics have improved our understanding of genetic syndromes associated with ASD, which has helped clarify distinct etiologies of ASD and document syndrome-specific profiles of neurocognitive strengths and weaknesses. Pediatric neuropsychologists have the potential to be impactful members of the care team for children with genetic syndromes and their families.

METHOD

We provide a critical review of the current literature related to the neuropsychological profiles of children with four genetic syndromes associated with ASD, including Tuberous Sclerosis Complex (TSC), fragile X syndrome (FXS), 22q11.2 deletion syndrome, and Angelman syndrome. Recommendations for assessment, intervention, and future directions are provided.

RESULTS

There is vast heterogeneity in terms of the cognitive, language, and developmental abilities of these populations. The within- and across-syndrome variability characteristic of genetic syndromes should be carefully considered during clinical evaluations, including possible measurement limitations, presence of intellectual disability, and important qualitative differences in the ASD-phenotypes across groups.

CONCLUSIONS

Individuals with genetic disorders pose challenging diagnostic and assessment questions. Pediatric neuropsychologists with expertise in neurodevelopmental processes are well suited to address these questions and identify profiles of neurocognitive strengths and weaknesses, tailor individualized recommendations, and provide diagnostic clarification.

Genomic Variation, Evolvability, and the Paradox of Mental Illness

Twentieth-century genetics was hard put to explain the irregular behavior of neuropsychiatric disorders. Autism and schizophrenia defy a principle of natural selection; they are highly heritable but associated with low reproductive success. Nevertheless, they persist. The genetic origins of such conditions are confounded by the problem of variable expression, that is, when a given genetic aberration can lead to any one of several distinct disorders. Also, autism and schizophrenia occur on a spectrum of severity, from mild and subclinical cases to the overt and disabling. Such irregularities reflect the problem of missing heritability; although hundreds of genes may be associated with autism or schizophrenia, together they account for only a small proportion of cases. Techniques for higher resolution, genomewide analysis have begun to illuminate the irregular and unpredictable behavior of the human genome. Thus, the origins of neuropsychiatric disorders in particular and complex disease in general have been illuminated. The human genome is characterized by a high degree of structural and behavioral variability: DNA content variation, epistasis, stochasticity in gene expression, and epigenetic changes. These elements have grown more complex as evolution scaled the phylogenetic tree. They are especially pertinent to brain development and function. Genomic variability is a window on the origins of complex disease, neuropsychiatric disorders, and neurodevelopmental disorders in particular. Genomic variability, as it happens, is also the fuel of evolvability. The genomic events that presided over the evolution of the primate and hominid lineages are over-represented in patients with autism and schizophrenia, as well as intellectual disability and epilepsy. That the special qualities of the human genome that drove evolution might, in some way, contribute to neuropsychiatric disorders is a matter of no little interest.

Young Adult Outcomes for Children With 22q11 Deletion Syndrome and Comorbid ADHD

Background

22q11.2 deletion syndrome (22q11DS) is a common microdeletion syndrome associated with a variety of negative health, cognitive, emotional, and behavioral outcomes. 22q11DS is comorbid with many psychiatric disorders including attention-deficit/hyperactivity disorder (ADHD). The current study aimed to investigate the cognitive, behavioral, and functional outcomes that a childhood ADHD diagnosis predicts to in adulthood.

Methods

This longitudinal study followed 52 individuals with 22q11DS over 9 years. Childhood ADHD was operationalized both categorically (Diagnostic and statistical manual - 4th edition (DSM-IV) ADHD diagnoses) and dimensionally (inattentive and hyperactive-impulsive symptoms) and was tested as predictors of young adult outcomes.

Results

As young adults, children with 22q11DS + baseline ADHD had more parent-reported executive dysfunction and lower levels of clinician-rated overall functioning than those with 22q11DS yet without ADHD. Dimensional symptoms of ADHD in childhood did not predict young adult outcomes. No self-report differences emerged between those with and without baseline ADHD. The majority (82.4%) of individuals with 22q11DS + baseline ADHD were never treated with an ADHD medication.

Conclusions

A categorical diagnosis of ADHD in childhood predicted a greater variety of worse outcomes than dimensional levels of ADHD symptoms. Despite the significant impact of comorbid ADHD in 22q11DS, evidence-based treatment rates were low.

Examining the durability of a hybrid, remote and computer-based cognitive remediation intervention for adolescents with 22q11.2 deletion syndrome

AIM

Schizophrenia and 22q11.2 deletion syndrome (22q11DS) share similar patterns of cognitive deficits. Up to 30% of those with 22q11DS develop schizophrenia during early adulthood. As cognitive decline has recently been found to predict onset of psychosis in adolescents with 22q11DS, early interventions such as cognitive remediation (CR) during adolescence are warranted. This paper investigates the durability of a remote, computerized, CR programme for youth with 22q11DS. Our aim was to determine if the positive effects of CR persisted 6 months beyond intervention completion.

METHODS

A longitudinal design with 21 participants serving as their own controls was used. Youth were seen for neurocognitive assessments at pre-treatment, after the targeted 8-month intervention, at post-treatment, and 6 months after for follow-up. During the intervention, cognitive coaches met remotely with participants for CR via video conferencing three times a week, and offered task-specific strategies. To determine if intervention improvements held across the 6-month follow-up period, neurocognitive measures were statistically examined with repeated measures analysis of variances from pre-treatment through follow-up.

RESULTS

Our CR intervention proved durable. Post-treatment improvements comprising cognitive flexibility, executive function, reaction time and working memory were maintained over the follow-up period.

CONCLUSIONS

Results confirm previous research regarding the durability of CR treatment and extend these findings to youth with 22q11DS. The present study may serve to inform early intervention efforts focused on cognitive and functionally relevant rehabilitation goals for youth with 22q11DS and suggests that 22q11DS can potentially serve as a suitable model for examining the trajectory preceding psychosis.

Examining the Overlap between Autism Spectrum Disorder and 22q11.2 Deletion Syndrome

22q11.2 deletion syndrome (22q11.2DS) is a genomic disorder reported to associate with autism spectrum disorders (ASDs) in 15–50% of cases; however, others suggest that individuals with 22q11.2DS present psychiatric or behavioral features associated with ASDs, but do not meet full criteria for ASD diagnoses. Such wide variability in findings may arise in part due to methodological differences across studies. Our study sought to determine whether individuals with 22q11.2DS meet strict ASD diagnostic criteria using research-based guidelines from the Collaborative Programs of Excellence in Autism (CPEA), which required a gathering of information from three sources: the Autism Diagnostic Interview-Revised (ADI-R), the Autism Diagnostic Observational Schedule (ADOS), and a clinician’s best-estimate diagnosis. Our study examined a cohort of children, adolescents, and young adults (n = 56) with 22q11.2DS, who were ascertained irrespective of parents’ behavioral or developmental concerns, and found that 17.9% (n = 10) of the participants met CPEA criteria for an ASD diagnosis, and that a majority showed some level of social-communication impairment or the presence of repetitive behaviors. We conclude that strictly defined ASDs occur in a substantial proportion of individuals with 22q11.2DS, and recommend that all individuals with 22q11.2DS be screened for ASDs during early childhood.

[Formula: see text]Executive functioning and its relation to ASD and ADHD symptomatology in 22q11.2 deletion syndrome

Children with 22q11.2 deletion syndrome (22q11DS; velo-cardio-facial-syndrome) are at risk for the developmental disorders, attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). In this study, the relation between executive functioning (EF) and the severity of ADHD and ASD symptoms is examined, since EF is known to be important in relation to emotional and behavioral problems. The participants consist of 58 children (38 females) with a mean age of 13.5 years (SD 2.6). Standardized assessment was used to evaluate the severity of ASD and ADHD symptomatology. The major aspects of EF, i.e., cognitive flexibility, inhibition, sustained attention, distractibility, working memory and reaction speed, were evaluated. The profile of EF in 22q11DS was found to be characterized by weaker performance compared to the norms on all subdomains of EF. Poor cognitive flexibility and inhibition, as well as high distractibility, were found to be related to more severe ASD symptoms, while poor quality of sustained attention and high distractibility were found to be related to more severe ADHD symptoms. It is concluded that children with 22q11DS experience impairments in EF, and that the degree of impairment on specific EF subdomains is related to the severity of ASD and/or ADHD symptomatology. These results may help in defining the mediating role of neurocognitive dysfunctions in the development of social and behavioral problems in 22q11DS.

Contribution of congenital heart disease to neuropsychiatric outcome in school-age children with 22q11.2 deletion syndrome

Children with 22q11.2 deletion syndrome (22q11DS) present with congenital heart disease (CHD) and high prevalence of psychiatric disorders and neurocognitive deficits. Although CHD has been implicated in neurodevelopment, its role in the neuropsychiatric outcome in 22q11DS is poorly understood. We investigated whether CHD contributes to the high prevalence of psychiatric disorders and neurocognitive impairments in 22q11DS. Fifty-four children ages 8-14 years with 22q11DS and 16 age-matched non-deleted children with CHD participated. They were assessed using semi-structured interviews and a Computerized Neurocognitive Battery. CHD status was assessed using available medical records. Prevalence of psychiatric disorders and cognitive profiles were compared among the groups. There were no significant differences between the prevalence of psychiatric disorders in the 22q11DS with and without CHD. In 22q11DS with CHD, the prevalence rates were 41% anxiety disorders, 37% ADHD and 71% psychosis spectrum. In 22q11DS without CHD, the rates were 33% anxiety disorders, 41% ADHD and 64% psychosis spectrum. In comparison, the non-deleted CHD group had lower rates of psychopathology (25% anxiety disorders, 6% ADHD, and 13% psychosis spectrum). Similarly, the 22q11DS groups, regardless of CHD status, had significantly greater neurocognitive deficits across multiple domains, compared to the CHD-only group. We conclude that CHD in this sample of children with 22q11.2DS does not have a major impact on the prevalence of psychiatric disorders and is not associated with increased neurocognitive deficits. These findings suggest that the 22q11.2 deletion status itself may confer significant neuropsychiatric vulnerability in this population.

Dysphagia and disrupted cranial nerve development in a mouse model of DiGeorge (22q11) deletion syndrome

We assessed feeding-related developmental anomalies in the LgDel mouse model of chromosome 22q11 deletion syndrome (22q11DS), a common developmental disorder that frequently includes perinatal dysphagia – debilitating feeding, swallowing and nutrition difficulties from birth onward – within its phenotypic spectrum. LgDel pups gain significantly less weight during the first postnatal weeks, and have several signs of respiratory infections due to food aspiration. Most 22q11 genes are expressed in anlagen of craniofacial and brainstem regions critical for feeding and swallowing, and diminished expression in LgDel embryos apparently compromises development of these regions. Palate and jaw anomalies indicate divergent oro-facial morphogenesis. Altered expression and patterning of hindbrain transcriptional regulators, especially those related to retinoic acid (RA) signaling, prefigures these disruptions. Subsequently, gene expression, axon growth and sensory ganglion formation in the trigeminal (V), glossopharyngeal (IX) or vagus (X) cranial nerves (CNs) that innervate targets essential for feeding, swallowing and digestion are disrupted. Posterior CN IX and X ganglia anomalies primarily reflect diminished dosage of the 22q11DS candidate gene Tbx1. Genetic modification of RA signaling in LgDel embryos rescues the anterior CN V phenotype and returns expression levels or pattern of RA-sensitive genes to those in wild-type embryos. Thus, diminished 22q11 gene dosage, including but not limited to Tbx1, disrupts oro-facial and CN development by modifying RA-modulated anterior-posterior hindbrain differentiation. These disruptions likely contribute to dysphagia in infants and young children with 22q11DS.

Axis I psychiatric diagnoses in adolescents and young adults with 22q11 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11DS) associates with schizophrenia spectrum disorders (SSDs), autism spectrum disorders (ASDs), and other psychiatric disorders, but co-occurrence of diagnoses are not well described.

METHODS

We evaluated the co-occurrence of SSDs, ASDs and other axis I psychiatric diagnoses in 31 adolescents and adults with 22q11DS, assessing ASDs using either stringent Collaborative Program for Excellence in Autism (ASD-CPEA) criteria, or less stringent DSM-IV criteria alone (ASD-DSM-IV).

RESULTS

Ten (32%) individuals met criteria for an SSD, five (16%) for ASD-CPEA, and five others (16%) for ASD-DSM-IV. Of those with ASD-CPEA, one (20%) met SSD criteria. Of those with ASD-DSM-IV, four (80%) met SSD criteria. Depressive disorders (8 individuals; 26%) and anxiety disorders (7; 23%) sometimes co-occurred with SSDs and ASDs. SSDs, ASDs, and anxiety occurred predominantly among males and depression predominantly among females.

CONCLUSIONS

Individuals with 22q11DS can manifest SSDs in the presence or absence of ASDs and other axis I diagnoses. The results suggest that standard clinical care should include childhood screening for ASDs, and later periodic screening for all axis I diagnoses.

How are autism and schizotypy related? Evidence from a non-clinical population

Both autism spectrum conditions (ASCs) and schizophrenia spectrum conditions (SSCs) involve altered or impaired social and communicative functioning, but whether these shared features indicate overlapping or different etiological factors is unknown. We outline three hypotheses (overlapping, independent, and diametric) for the possible relationship between ASCs and SSCs, and compare their predictions for the expected relationships between autistic and schizotypal phenotypes using the Autism Spectrum Quotient and the Schizotypal Personality Questionnaire-Brief Revised from a large non-clinical sample of undergraduate students. Consistent with previous research, autistic features were positively associated with several schizotypal features, with the most overlap occurring between interpersonal schizotypy and autistic social and communication phenotypes. The first component of a principal components analysis (PCA) of subscale scores reflected these positive correlations, and suggested the presence of an axis (PC1) representing general social interest and aptitude. By contrast, the second principal component (PC2) exhibited a pattern of positive and negative loadings indicative of an axis from autism to positive schizotypy, such that positive schizotypal features loaded in the opposite direction to core autistic features. These overall PCA patterns were replicated in a second data set from a Japanese population. To evaluate the validity of our interpretation of the PCA results, we measured handedness and mental rotation ability, as these are established correlates of SSCs and ASCs, respectively. PC2 scores were significantly associated with hand preference, such that increasingly 'schizotypal' scores predicted reduced strength of handedness, which is consistent with previous research. PC1 scores were positively related to performance on the mental rotation task, suggesting trade-offs between social skills and visual-spatial ability. These results provide novel evidence for an autism-positive schizotypy axis, and highlight the importance of recognizing that psychological variation involving reduced social interest and functioning may have diverse causes.

Rare CNVs and tag SNPs at 15q11.2 are associated with schizophrenia in the Han Chinese population

BACKGROUND

Rare copy number variations (CNVs) were involved in the etiology of neuropsychiatric disorders, and some of them appeared to be shared risk factors for several different diseases. One of those promising loci is the CNV at 15q11.2, including 4 genes, TUBGCP5, CYFIP1, NIPA2, and NIPA1. Several studies showed that microdeletions at this locus were significant associated with schizophrenia. In the current study, we investigated the role of both rare CNVs and common single nucleotide polymorphisms (SNPs) at 15q11.2 in schizophrenia in the Chinese Han population.

METHODS

We screened deletions at 15q11.2 in 2058 schizophrenia patients and 3275 normal controls in Chinese Han population by Affymetrix 500K/6.0 SNP arrays and SYBR green real-time polymerase chain reaction and then validated deletions by multiplex ligation-dependent probe amplification and Taqman real-time assays. We successfully genotyped 27 tag SNPs in total and tested associations in 1144 schizophrenia cases and 1144 normal controls.

RESULTS

We found a triple increase of deletions in cases over controls, with OR=4.45 (95% CI=1.36-14.60) and P=.014. In the analysis of common SNPs, we found that the most significant SNP in schizophrenia was rs4778334 (OR=.72, 95% CI=0.60-0.87, allelic P=.0056 after permutation, genotypic P=.015 after permutation). We also found SNP rs1009153 in CYFIP1 was associated with schizophrenia (OR=0.82, 95% CI=0.73-0.93, allelic P=.044 after permutation).

CONCLUSION

We found that both rare deletions and common variants at 15q11.2 were associated with schizophrenia in the Chinese Han population.

22q11 deletion syndrome: a review of the neuropsychiatric features and their neurobiological basis

The 22q11.2 deletion syndrome (22q11DS) is caused by an autosomal dominant microdeletion of chromosome 22 at the long arm (q) 11.2 band. The 22q11DS is among the most clinically variable syndromes, with more than 180 features related with the deletion, and is associated with an increased risk of psychiatric disorders, accounting for up to 1%-2% of schizophrenia cases. In recent years, several genes located on chromosome 22q11 have been linked to schizophrenia, including those encoding catechol-O-methyltransferase and proline dehydrogenase, and the interaction between these and other candidate genes in the deleted region is an important area of research. It has been suggested that haploinsufficiency of some genes within the 22q11.2 region may contribute to the characteristic psychiatric phenotype and cognitive functioning of schizophrenia. Moreover, an extensive literature on neuroimaging shows reductions of the volumes of both gray and white matter, and these findings suggest that this reduction may be predictive of increased risk of prodromal psychotic symptoms in 22q11DS patients. Experimental and standardized cognitive assessments alongside neuroimaging may be important to identify one or more endophenotypes of schizophrenia, as well as a predictive prodrome that can be preventively treated during childhood and adolescence. In this review, we summarize recent data about the 22q11DS, in particular those addressing the neuropsychiatric and cognitive phenotypes associated with the deletion, underlining the recent advances in the studies about the genetic architecture of the syndrome.

Can genetics inform the management of cognitive deficits in schizophrenia?

There is no doubt that schizophrenia has a significant genetic component and a number of candidate genes have been identified for this debilitating disorder. Of note, several of these are implicated in cognition. Cognitive deficits constitute core symptoms of schizophrenia, and while current antipsychotic treatment strategies aim to help psychosis-related symptomatology, the cognitive symptom domain is largely inadequately treated. A number of other pharmacological approaches (e.g. using drugs that target specific neurotransmitter systems) have also been attempted for the amelioration of cognitive deficits in this population; however, these too have had limited success so far. Psychological interventions appear promising, though there has been speculation regarding whether or not these produce long-term functional improvements. Pharmacogenetic studies of the cognitive effects of currently available antipsychotics, although in relatively early stages, suggest that the treatment of cognitive deficits in schizophrenia may be advanced by focusing on genetic variants associated with specific cognitive dysfunctions in the general population and using this to match the most relevant pharmacological and/or psychological interventions with the genetic and cognitive profiles of the target population. Such a strategy would encourage bottom-up advances in drug development and provide a platform for individualised treatment of cognitive deficits in schizophrenia.

Copy number variants: a new molecular frontier in clinical psychiatry

Molecular genetic research, building on genetic epidemiology, has provided the field of psychiatry with a host of exciting advances. It is now clear beyond any reasonable doubt that genetic inheritance influences liability to develop almost every major psychiatric disorder. Rapid progress in identifying genes contributing to psychiatric liability, recently accelerated by the advent of approaches such as genome-wide association studies and chromosomal microarray analysis, raises a critical question for psychiatric practice and training: how will molecular genetics alter the practice of psychiatry for front-line clinicians? The premise of the present review is that our growing knowledge regarding the roles of copy number variants in behavioral disorders will soon require revision of standards of evaluation and care for psychiatric patients.

Gamma synchrony: towards a translational biomarker for the treatment-resistant symptoms of schizophrenia

The lack of efficacy for antipsychotics with respect to negative symptoms and cognitive deficits is a significant obstacle for the treatment of schizophrenia. Developing new drugs to target these symptoms requires appropriate neural biomarkers that can be investigated in model organisms, be used to track treatment response, and provide insight into pathophysiological disease mechanisms. A growing body of evidence indicates that neural oscillations in the gamma frequency range (30-80 Hz) are disturbed in schizophrenia. Gamma synchrony has been shown to mediate a host of sensory and cognitive functions, including perceptual encoding, selective attention, salience, and working memory - neurocognitive processes that are dysfunctional in schizophrenia and largely refractory to treatment. This review summarizes the current state of clinical literature with respect to gamma-band responses (GBRs) in schizophrenia, focusing on resting and auditory paradigms. Next, preclinical studies of schizophrenia that have investigated gamma-band activity are reviewed to gain insight into neural mechanisms associated with these deficits. We conclude that abnormalities in gamma synchrony are ubiquitous in schizophrenia and likely reflect an elevation in baseline cortical gamma synchrony ('noise') coupled with reduced stimulus-evoked GBRs ('signal'). Such a model likely reflects hippocampal and cortical dysfunction, as well as reduced glutamatergic signaling with downstream GABAergic deficits, but is probably less influenced by dopaminergic abnormalities implicated in schizophrenia. Finally, we propose that analogous signal-to-noise deficits in the flow of cortical information in preclinical models are useful targets for the development of new drugs that target the treatment-resistant symptoms of schizophrenia.

Neurobiology and phenotypic expression in early onset schizophrenia

AIM

Early-onset schizophrenia (onset before adulthood) is a rare and severe form of the disorder that shows phenotypic and neurobiological continuity with adult-onset schizophrenia. Here, we provide a synthesis of keynote findings in this enriched population to understand better the neurobiology and pathophysiology of early-onset schizophrenia.

METHODS

A synthetic and integrative approach is applied to review studies stemming from epidemiology, phenomenology, cognition, genetics and neuroimaging data. We provide conclusions and future directions of research on early-onset schizophrenia.

RESULTS

Childhood and adolescent-onset schizophrenia is associated with severe clinical course, greater rates of premorbid abnormalities, poor psychosocial functioning and increased severity of brain abnormalities. Early-onset cases show similar neurobiological correlates and phenotypic deficits to adult-onset schizophrenia, but show worse long-term psychopathological outcome. Emerging technological advances have provided important insights into the genomic architecture of early-onset schizophrenia, suggesting that some genetic variations may occur more frequently and at a higher rate in young-onset than adult-onset cases.

CONCLUSIONS

Clinical, cognitive, genetic and imaging data suggest increased severity in early-onset schizophrenia. Studying younger-onset cases can provide useful insights into the neurobiological mechanisms of schizophrenia and the complexity of gene-environment interactions leading to the emergence of this debilitating disorder.

The diagnostic concept of schizophrenia: its history, evolution, and future prospects

More than a century since the delineation of dementia praecox by Kraepelin, the etiology, neuropathology and pathophysiology of schizophrenia remain elusive. Despite the availability of criteria allowing reliable diagnostic identification, schizophrenia essentially remains a broad clinical syndrome defined by reported subjective experiences (symptoms), loss of function (behavioral impairments), and variable patterns of course. Research has identified a number of putative biological markers associated with the disorder, including neurocognitive dysfunction, brain dysmorphology, and neurochemical abnormalities. Yet none of these variables has to date been definitively proven to possess the sensitivity and specificity expected of a diagnostic test. Genetic linkage and association studies have targeted multiple candidate loci and genes, but failed to demonstrate that any specif ic gene variant, or a combination of genes, is either necessary or sufficient to cause schizophrenia. Thus, the existence of a specific brain disease underlying schizophrenia remains a hypothesis. Against a background of an ever-increasing volume of research data, the inconclusiveness of the search for causes of the disorder fuels doubts about the validity of the schizophrenia construct as presently defined. Given the protean nature of the symptoms of schizophrenia and the poor coherence of the clinical and biological findings, such doubts are not without reason. However, simply dismantling the concept is unlikely to result in an alternative model that would account for the host of clinical phenomena and research data consistent with a disease hypothesis of schizophrenia. For the time being, the clinical concept of schizophrenia is supported by empirical evidence that its multiple facets form a broad syndrome with non-negligible internal cohesion and a characteristic evolution over time. The dissection of the syndrome with the aid of endophenotypes is beginning to be perceived as a promising approach in schizophrenia genetics.

Mitochondrial dysfunction and pathology in bipolar disorder and schizophrenia

Bipolar disorder (BPD) and schizophrenia (SZ) are severe psychiatric illnesses with a combined prevalence of 4%. A disturbance of energy metabolism is frequently observed in these disorders. Several pieces of evidence point to an underlying dysfunction of mitochondria: (i) decreased mitochondrial respiration; (ii) changes in mitochondrial morphology; (iii) increases in mitochondrial DNA (mtDNA) polymorphisms and in levels of mtDNA mutations; (iv) downregulation of nuclear mRNA molecules and proteins involved in mitochondrial respiration; (v) decreased high-energy phosphates and decreased pH in the brain; and (vi) psychotic and affective symptoms, and cognitive decline in mitochondrial disorders. Furthermore, transgenic mice with mutated mitochondrial DNA polymerase show mood disorder-like phenotypes. In this review, we will discuss the genetic and physiological components of mitochondria and the evidence for mitochondrial abnormalities in BPD and SZ. We will furthermore describe the role of mitochondria during brain development and the effect of current drugs for mental illness on mitochondrial function. Understanding the role of mitochondria, both developmentally as well as in the ailing brain, is of critical importance to elucidate pathophysiological mechanisms in psychiatric disorders.

Rare structural variants in schizophrenia: one disorder, multiple mutations; one mutation, multiple disorders

Recent studies have established an important role for rare genomic deletions and duplications in the etiology of schizophrenia. This research suggests that the genetic architecture of neuropsychiatric disorders includes a constellation of rare mutations in many different genes. Mutations that confer substantial risk for schizophrenia have been identified at several loci, most of which have also been implicated in other neurodevelopmental disorders, including autism. Genetic heterogeneity is a characteristic of schizophrenia; conversely, phenotypic heterogeneity is a characteristic of all schizophrenia-associated mutations. Both kinds of heterogeneity probably reflect the complexity of neurodevelopment. Research strategies must account for both genetic and clinical heterogeneity to identify the genes and pathways crucial for the development of neuropsychiatric disorders.

Microduplications of 16p11.2 are associated with schizophrenia

Recurrent microdeletions and microduplications of a 600-kb genomic region of chromosome 16p11.2 have been implicated in childhood-onset developmental disorders. We report the association of 16p11.2 microduplications with schizophrenia in two large cohorts. The microduplication was detected in 12/1,906 (0.63%) cases and 1/3,971 (0.03%) controls (P = 1.2 x 10(-5), OR = 25.8) from the initial cohort, and in 9/2,645 (0.34%) cases and 1/2,420 (0.04%) controls (P = 0.022, OR = 8.3) of the replication cohort. The 16p11.2 microduplication was associated with a 14.5-fold increased risk of schizophrenia (95% CI (3.3, 62)) in the combined sample. A meta-analysis of datasets for multiple psychiatric disorders showed a significant association of the microduplication with schizophrenia (P = 4.8 x 10(-7)), bipolar disorder (P = 0.017) and autism (P = 1.9 x 10(-7)). In contrast, the reciprocal microdeletion was associated only with autism and developmental disorders (P = 2.3 x 10(-13)). Head circumference was larger in patients with the microdeletion than in patients with the microduplication (P = 0.0007).

Performance on the Modified Card Sorting Test and its relation to psychopathology in adolescents and young adults with 22q11.2 deletion syndrome

BACKGROUND

Approximately one-third of individuals with 22q11.2 deletion syndrome (22q11DS), a common genetic disorder highly associated with intellectual disabilities, may develop schizophrenia, likely preceded by a mild to moderate cognitive decline.

METHODS

We examined adolescents and young adults with 22q11DS for the presence of executive function deficits using a modified version of the Wisconsin Card Sorting Test (MCST) and assessed whether specific performances were associated with concurrent schizophrenia-prodrome symptoms. We also examined possible relationships between MCST performance and broader indices of psychopathology, including self-reported internalising and externalising behavioural symptoms.

RESULTS

Participants with 22q11DS scored significantly below age-matched controls on seven out of nine MCST measures, and poorer MCST performance was associated with increased positive prodromal and internalising behavioural symptoms.

CONCLUSIONS

The schizophrenia-prodrome in 22q11DS involves executive dysfunction, and longitudinal investigation is necessary to examine if specific executive function impairments precedes or co-occurs with the emergence of behavioural psychopathology.

Refining the 22q11.2 deletion breakpoints in DiGeorge syndrome by aCGH

Hemizygous deletions of the chromosome 22q11.2 region result in the 22q11.2 deletion syndrome also referred to as DiGeorge, Velocardiofacial or Shprintzen syndromes. The phenotype is variable but commonly includes conotruncal cardiac defects, palatal abnormalities, learning and behavioral problems, immune deficiency, and facial anomalies. Four distinct highly homologous blocks of low copy number repeat sequences (LCRs) flank the deletion region. Mispairing of LCRs during meiosis with unequal meiotic exchange is assumed to cause the recurrent and consistent deletions. The proximal LCR is reportedly located at 22q11.2 from 17.037 to 17.083 Mb while the distal LCR is located from 19.835 to 19.880 Mb. Although the chromosome breakpoints are thought to localize to the LCRs, the positions of the breakpoints have been investigated in only a few individuals. Therefore, we used high resolution oligonucleotide-based 244K microarray comparative genomic hybridization (aCGH) to resolve the breakpoints in a cohort of 20 subjects with known 22q11.2 deletions. We also investigated copy number variation (CNV) in the rest of the genome. The 22q11.2 breaks occurred on either side of the LCR in our subjects, although more commonly on the distal side of the reported proximal LCR. The proximal breakpoints in our subjects spanned the region from 17.036 to 17.398 Mb. This region includes the genes DGCR6 (DiGeorge syndrome critical region protein 6) and PRODH (proline dehydrogenase 1), along with three open reading frames that may encode proteins of unknown function. The distal breakpoints spanned the region from 19.788 to 20.122 Mb. This region includes the genes GGT2 (gamma-glutamyltransferase-like protein 2), HIC2 (hypermethylated in cancer 2), and multiple transcripts of unknown function. The genes in these two breakpoint regions are variably hemizygous depending on the location of the breakpoints. Our 20 subjects had 254 CNVs throughout the genome, 94 duplications and 160 deletions, ranging in size from 1 kb to 2.4 Mb. The presence or absence of genes at the breakpoints depending on the size of the deletion plus variation in the rest of the genome due to CNVs likely contribute to the variable phenotype associated with the 22q11.2 deletion or DiGeorge syndrome.

The genetics of childhood-onset schizophrenia: when madness strikes the prepubescent

Stratification by age at onset has been useful for genetic studies across all of medicine. For the past 20 years, the National Institute of Mental Health has been systematically recruiting patients with onset of schizophrenia before age 13 years. Examination of familial transmission of known candidate risk genes was carried out, and a 10% rate of cytogenetic abnormalities was found. Most recently, high-density, array-based scans for submicroscopic rare copy number variations (CNVs) have suggested that this kind of genetic variation occurs more frequently than expected by chance in childhood-onset schizophrenia (COS) and at a higher rate than observed in adult-onset disorder. Several CNVs and cytogenetic abnormalities associated with COS are also seen in autism and mental retardation. Populations with COS may have more salient genetic influence than adult-onset cases. The relationship of rare CNVs to prepsychotic development is being studied further.

Support for the involvement of large copy number variants in the pathogenesis of schizophrenia

We investigated the involvement of rare (<1%) copy number variants (CNVs) in 471 cases of schizophrenia and 2792 controls that had been genotyped using the Affymetrix GeneChip 500K Mapping Array. Large CNVs >1 Mb were 2.26 times more common in cases (P = 0.00027), with the effect coming mostly from deletions (odds ratio, OR = 4.53, P = 0.00013) although duplications were also more common (OR = 1.71, P = 0.04). Two large deletions were found in two cases each, but in no controls: a deletion at 22q11.2 known to be a susceptibility factor for schizophrenia and a deletion on 17p12, at 14.0-15.4 Mb. The latter is known to cause hereditary neuropathy with liability to pressure palsies. The same deletion was found in 6 of 4618 (0.13%) cases and 6 of 36 092 (0.017%) controls in the re-analysed data of two recent large CNV studies of schizophrenia (OR = 7.82, P = 0.001), with the combined significance level for all three studies achieving P = 5 x 10(-5). One large duplication on 16p13.1, which has been previously implicated as a susceptibility factor for autism, was found in three cases and six controls (0.6% versus 0.2%, OR = 2.98, P = 0.13). We also provide the first support for a recently reported association between deletions at 15q11.2 and schizophrenia (P = 0.026). This study confirms the involvement of rare CNVs in the pathogenesis of schizophrenia and contributes to the growing list of specific CNVs that are implicated.

Age-related gene expression in Tourette syndrome

Because infection and immune responses have been implicated in the pathogenesis of Tourette syndrome (TS), we hypothesized that children with TS would have altered gene expression in blood compared to controls. In addition, because TS symptoms in childhood vary with age, we tested whether gene expression changes that occur with age in TS differ from normal control children. Whole blood was obtained from 30 children and adolescents with TS and 28 healthy children and adolescents matched for age, race, and gender. Gene expression (RNA) was assessed using whole genome Affymetrix microarrays. Age was analyzed as a continuous covariate and also stratified into three groups: 5-9 (common age for tic onset), 10-12 (when tics often peak), and 13-16 (tics may begin to wane). No global differences were found between TS and controls. However, expression of many genes and multiple pathways differed between TS and controls within each age group (5-9, 10-12, and 13-16), including genes involved in the immune-synapse, and proteasome- and ubiquitin-mediated proteolysis pathways. Notably, across age strata, expression of interferon response, viral processing, natural killer and cytotoxic T-lymphocyte cell genes differed. Our findings suggest age-related interferon, immune and protein degradation gene expression differences between TS and controls.

Multiplex ligation-dependent probe amplification for genetic screening in autism spectrum disorders: efficient identification of known microduplications and identification of a novel microduplication in ASMT

Background

It has previously been shown that specific microdeletions and microduplications, many of which also associated with cognitive impairment (CI), can present with autism spectrum disorders (ASDs). Multiplex ligation-dependent probe amplification (MLPA) represents an efficient method to screen for such recurrent microdeletions and microduplications.

Methods

In the current study, a total of 279 unrelated subjects ascertained for ASDs were screened for genomic disorders associated with CI using MLPA. Fluorescence in situ hybridization (FISH), quantitative polymerase chain reaction (Q-PCR) and/or direct DNA sequencing were used to validate potential microdeletions and microduplications. Methylation-sensitive MLPA was used to characterize individuals with duplications in the Prader-Willi/Angelman (PWA) region.

Results

MLPA showed two subjects with typical ASD-associated interstitial duplications of the 15q11-q13 PWA region of maternal origin. Two additional subjects showed smaller, de novo duplications of the PWA region that had not been previously characterized. Genes in these two novel duplications include GABRB3 and ATP10A in one case, and MKRN3, MAGEL2 and NDN in the other. In addition, two subjects showed duplications of the 22q11/DiGeorge syndrome region. One individual was found to carry a 12 kb deletion in one copy of the ASPA gene on 17p13, which when mutated in both alleles leads to Canavan disease. Two subjects showed partial duplication of the TM4SF2 gene on Xp11.4, previously implicated in X-linked non-specific mental retardation, but in our subsequent analyses such variants were also found in controls. A partial duplication in the ASMT gene, located in the pseudoautosomal region 1 (PAR1) of the sex chromosomes and previously suggested to be involved in ASD susceptibility, was observed in 6–7% of the cases but in only 2% of controls (P = 0.003).

Conclusion

MLPA proves to be an efficient method to screen for chromosomal abnormalities. We identified duplications in 15q11-q13 and in 22q11, including new de novo small duplications, as likely contributing to ASD in the current sample by increasing liability and/or exacerbating symptoms. Our data indicate that duplications in TM4SF2 are not associated with the phenotype given their presence in controls. The results in PAR1/PAR2 are the first large-scale studies of gene dosage in these regions, and the findings at the ASMT locus indicate that further studies of the duplication of the ASMT gene are needed in order to gain insight into its potential involvement in ASD. Our studies also identify some limitations of MLPA, where single base changes in probe binding sequences alter results. In summary, our studies indicate that MLPA, with a focus on accepted medical genetic conditions, may be an inexpensive method for detection of microdeletions and microduplications in ASD patients for purposes of genetic counselling if MLPA-identified deletions are validated by additional methods.

Living with a child at risk for psychotic illness: the experience of parents coping with 22q11 deletion syndrome: an exploratory study

Patients with 22q11 deletion syndrome (22q11DS) have a 25-30% risk of developing schizophrenia, as well as an increased risk for other psychiatric illnesses including bipolar and schizo-affective disease. As a result, their families may be informed of a risk for psychotic illness years or even decades before the likely age of onset. We performed an exploratory study, surveying 41 caretakers of individuals with 22q11DS, and found that information about the association between 22q11DS and psychiatric disease was omitted at diagnosis a majority of the time and rarely addressed subsequently by pediatricians or other medical specialists, including medical geneticists. Families frequently received their information only from non-medical sources, principally the Internet. Individuals with 22q11DS often have many medical issues, but a majority of parents indicated that the risk of psychotic illness was their greatest source of anxiety. Looking at how predictive information affects those who receive it is an important adjunct to the development of genetic testing; the experience of these families suggests that in order to use the information to improve outcomes or modify risk it is necessary to receive it in the context of ongoing support and access to resources.

Mitochondrial localization and function of a subset of 22q11 deletion syndrome candidate genes

Six genes in the 1.5 Mb region of chromosome 22 deleted in DiGeorge/22q11 deletion syndrome-Mrpl40, Prodh, Slc25a1, Txnrd2, T10, and Zdhhc8-encode mitochondrial proteins. All six genes are expressed in the brain, and maximal expression coincides with peak forebrain synaptogenesis shortly after birth. Furthermore, their protein products are associated with brain mitochondria, including those in synaptic terminals. Among the six, only Zddhc8 influences mitochondria-regulated apoptosis when overexpressed, and appears to interact biochemically with established mitochondrial proteins. Zdhhc8 has an apparent interaction with Uqcrc1, a component of mitochondrial complex III. The two proteins are coincidently expressed in pre-synaptic processes; however, Zdhhc8 is more frequently seen in glutamatergic terminals. 22q11 deletion may alter metabolic properties of cortical mitochondria during early post-natal life, since expression complex III components, including Uqcrc1, is significantly increased at birth in a mouse model of 22q11 deletion, and declines to normal values in adulthood. Our results suggest that altered dosage of one, or several 22q11 mitochondrial genes, particularly during early post-natal cortical development, may disrupt neuronal metabolism or synaptic signaling.

Co-occurrence of ADHD and autism spectrum disorders: phenomenology and treatment

The Diagnostic and Statistical Manual of Mental Disorders (4th Edition) prohibits the co-diagnosis of attention-deficit/hyperactivity disorder (ADHD) and an autism spectrum disorder (ASD). However, recent studies indicate that co-occurrence of clinically significant ADHD and autistic symptoms is common, and that some genes may influence both disorders. Children with the combination of ADHD and motor coordination problems are particularly likely to have an ASD. These co-occurrences of symptoms are important since children with ASD in addition to ADHD symptoms may respond poorly to standard ADHD treatments or have increased side effects. Such children may benefit from additional classes of pharmacologic agents (i.e., alpha-agonists, selective serotonin reuptake inhibitors and neuroleptics). They may also benefit from social skills therapy, individual and family psychotherapy, behavioral therapy and other nonpharmacologic interventions.