Bridging the gene-behavior divide through neuroimaging deletion syndromes: Velocardiofacial (22q11.2 Deletion) and Williams (7q11.23 Deletion) syndromes

Levodopa-responsive dystonia, parkinsonism, and treatment-resistant schizoaffective disorder in Williams syndrome

BACKGROUND

Williams syndrome (WS; chromosome 7q11.23 deletion) is a rare, multisystemic, neurodevelopmental disorder with variable penetrance and expressivity. Although movement and psychiatric disorders are known to occur in individuals with WS, parkinsonism, dystonia, and treatment-resistant schizoaffective disorder have not been formally described.

METHODS

We present two unrelated cases of adults with molecularly confirmed WS and typical histories of developmental delays, intellectual/learning disabilities, and treatment-responsive anxiety/mood disorder who developed similar noteworthy neuropsychiatric expressions. We reviewed detailed neuropsychiatric histories, laboratory investigations, neuroimaging, and treatment responses and compared data for the two cases.

RESULTS

Both individuals developed treatment-resistant schizoaffective disorder in adulthood requiring multiple trials of antipsychotic treatments. While on clozapine, both patients developed parkinsonism and generalized dystonia with truncal involvement that responded to trials of low-dose levodopa without exacerbating underlying psychotic or affective symptoms.

CONCLUSION

This report illustrates the novel occurrence of levodopa-responsive movement disorders and treatment-resistant schizoaffective disorder in individuals with WS, adding to the expanding neuropsychiatric phenotypes, and highlighting potential shared underlying mechanisms. The observed treatment response suggests that levodopa, in relatively low doses, may be safe and useful in ameliorating presumed antipsychotic-associated parkinsonism and tardive dystonia in WS.

Neuroemergentism: A Framework for Studying Cognition and the Brain

There has been virtual explosion of studies published in cognitive neuroscience primarily due to increased accessibility to neuroimaging methods, which has led to different approaches in interpretation. This review seeks to synthesize both developmental approaches and more recent views that consider neuroimaging. The ways in which Neuronal Recycling, Neural Reuse, and Language as Shaped by the Brain perspectives seek to clarify the brain bases of cognition will be addressed. Neuroconstructivism as an additional explanatory framework which seeks to bind brain and cognition to development will also be presented. Despite sharing similar goals, the four approaches to understanding how the brain is related to cognition have generally been considered separately. However, we propose that all four perspectives argue for a form of Emergentism in which combinations of smaller elements can lead to a greater whole. This discussion seeks to provide a synthesis of these approaches that leads to the emergence of a theory itself. We term this new synthesis Neurocomputational Emergentism (or Neuromergentism for short).

Recurrent reciprocal copy number variants: Roles and rules in neurodevelopmental disorders

Deletions and duplications, called reciprocal CNVs when they occur at the same locus, are implicated in neurodevelopmental phenotypes ranging from morphological to behavioral. In this article, we propose three models of how differences in gene expression in deletion and duplication genotypes may result in deleterious phenotypes. To explore these models, we use examples of the similarities and differences in clinical phenotypes of five reciprocal CNVs known to cause neurodevelopmental disorders: 1q21.1, 7q11.23, 15q13.3, 16p11.2, and 22q11.2. These models and examples may inform some insights into better understanding of gene-phenotype relationships. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 519-530, 2018.

A Common Polymorphism in a Williams Syndrome Gene Predicts Amygdala Reactivity and Extraversion in Healthy Adults

BACKGROUND

Williams syndrome (WS), a genetic disorder resulting from hemizygous microdeletion of chromosome 7q11.23, has emerged as a model for identifying the genetic architecture of socioemotional behavior. Common polymorphisms in GTF2I, which is found within the WS microdeletion, have been associated with reduced social anxiety in the general population. Identifying neural phenotypes affected by these polymorphisms would help advance our understanding not only of this specific genetic association but also of the broader neurogenetic mechanisms of variability in socioemotional behavior.

METHODS

Through an ongoing parent protocol, the Duke Neurogenetics Study, we measured threat-related amygdala reactivity to fearful and angry facial expressions using functional magnetic resonance imaging, assessed trait personality using the Revised NEO Personality Inventory, and imputed GTF2I rs13227433 from saliva-derived DNA using custom Illumina arrays. Participants included 808 non-Hispanic Caucasian, African American, and Asian university students.

RESULTS

The GTF2I rs13227433 AA genotype, previously associated with lower social anxiety, predicted decreased threat-related amygdala reactivity. An indirect effect of GTF2I genotype on the warmth facet of extraversion was mediated by decreased threat-related amygdala reactivity in women but not men.

CONCLUSIONS

A common polymorphism in the WS gene GTF2I associated with reduced social anxiety predicts decreased threat-related amygdala reactivity, which mediates an association between genotype and increased warmth in women. These results are consistent with reduced threat-related amygdala reactivity in WS and suggest that common variation in GTF2I contributes to broader variability in socioemotional brain function and behavior, with implications for understanding the neurogenetic bases of WS as well as social anxiety.

Does degree of gyrification underlie the phenotypic and genetic associations between cortical surface area and cognitive ability?

The phenotypic and genetic relationship between global cortical size and general cognitive ability (GCA) appears to be driven by surface area (SA) and not cortical thickness (CT). Gyrification (cortical folding) is an important property of the cortex that helps to increase SA within a finite space, and may also improve connectivity by reducing distance between regions. Hence, gyrification may be what underlies the SA-GCA relationship. In previous phenotypic studies, a 3-dimensional gyrification index (3DGI) has been positively associated with cognitive ability and negatively associated with mild cognitive impairment, Alzheimer's disease, and psychiatric disorders affecting cognition. However, the differential genetic associations of 3DGI and SA with GCA are still unclear. We examined the heritability of 3DGI, and the phenotypic, genetic, and environmental associations of 3DGI with SA and GCA in a large sample of adult male twins (N = 512). Nearly 85% of the variance in 3DGI was due to genes, and 3DGI had a strong phenotypic and genetic association with SA. Both 3DGI and total SA had positive phenotypic correlations with GCA. However, the SA-GCA correlation remained significant after controlling for 3DGI, but not the other way around. There was also significant genetic covariance between SA and GCA, but not between 3DGI and GCA. Thus, despite the phenotypic and genetic associations between 3DGI and SA, our results do not support the hypothesis that gyrification underlies the association between SA and GCA.

Incidental radiologic findings in the 22q11.2 deletion syndrome

BACKGROUND AND PURPOSE

The 22q11.2 deletion syndrome is a common genetic microdeletion syndrome that results in cognitive delays and an increased risk of several psychiatric disorders, particularly schizophrenia. The current study investigates the prevalence of incidental neuroradiologic findings within this population and their relationships with psychiatric conditions.

MATERIALS AND METHODS

Brain MR imaging from 58 individuals with 22q11.2 deletion syndrome was reviewed by board-certified radiologists by using standard clinical procedures. Intracranial incidental findings were classified into 8 categories and compared with a large typically developing cohort.

RESULTS

The rate of incidental findings was significantly higher (P < .0001) in 22q11.2 deletion syndrome compared with typically developing individuals, driven by a high prevalence of cavum septum pellucidum (19.0%) and white matter abnormalities (10.3%). Both of these findings were associated with psychosis in 22q11.2 deletion syndrome.

CONCLUSIONS

Cavum septum pellucidum and white matter hyperintensities are significantly more prevalent in patients with the 22q11.2 deletion syndrome and may represent biomarkers for psychosis.

Shyness discriminates between children with 22q11.2 deletion syndrome and Williams syndrome and predicts emergence of psychosis in 22q11.2 deletion syndrome

Background

22q11.2 deletion syndrome (22q11.2DS) is a common neurogenetic syndrome associated with high rates of psychosis. The aims of the present study were to identify the unique temperament traits that characterize children with 22q11.2DS compared to children with Williams syndrome (WS) and typically developing (TD) controls, and to examine temperamental predictors of the emergence of psychosis in 22q11.2DS.

Methods

The temperament of 55 children with 22q11.2DS, 36 with WS, and 280 TD children was assessed using the Emotionality, Activity, Sociability (EAS) Temperament Survey, Parental Ratings. The presence of a psychotic disorder was evaluated in 49 children and adolescents with 22q11.2DS at baseline and again 5.43 ± 2.23 years after baseline temperament assessment.

Results

Children with 22q11.2DS scored higher on Shyness compared to WS and TD controls. Children with 22q11.2DS and WS scored higher on Emotionality and lower on Activity compared to TD controls. Shyness was more severe in older compared to younger children with 22q11.2DS. Baseline Shyness scores significantly predicted the later emergence of a psychotic disorder at follow-up, in children with 22q11.2DS.

Conclusions

Our results suggest that shyness is an early marker associated with the later emergence of psychosis in 22q11.2DS.

Looking and thinking: how individuals with Williams syndrome make judgements about mental states

Individuals with the neuro-developmental disorder Williams syndrome (WS) are characterised by a combination of features which makes this group vulnerable socially, including mild-moderate cognitive difficulties, pro-social drive, and indiscriminate trust. The purpose of this study was to explore a key socio-communicative skill in individuals with WS, namely, mental state recognition abilities. We explored this skill in a detailed way by looking at how well individuals with WS recognise complex everyday mental states, and how they allocate their attention while making these judgements. Participants with WS were matched to two typically developing groups for comparison purposes, a verbal ability matched group and a chronological age matched group. While eye movements were recorded, participants were shown displays of eight different mental states in static and dynamic form, and they performed a forced-choice judgement on the mental state. Mental states were easier to recognise in dynamic form rather than static form. Mental state recognition ability for individuals with WS was poorer than expected by their chronological age, and at the level expected by their verbal ability. However, the pattern of mental state recognition for participants with WS varied according to mental state, and we found some interesting links between ease/difficulty recognising some mental states (worried/do not trust) and the classic behavioural profile associated with WS (high anxiety/indiscriminate trust). Furthermore, eye tracking data revealed that participants with WS allocated their attention atypically, with less time spent attending the information from the face regions. This challenges the widely held understanding of WS being associated with prolonged face and eye gaze, and indicates that there is more heterogeneity within this disorder in terms of socio-perception than previous reports would suggest.

Tbx1 regulates brain vascularization

The transcription factor TBX1 is the major gene involved in 22q11.2 deletion syndrome (22q11.2DS). Using mouse models of these diseases, we have previously shown that TBX1 activates VEGFR3 in endothelial cells (EC), and that this interaction is critical for the development of the lymphatic vasculature. In this study, we show that TBX1 regulates brain angiogenesis. Using loss-of-function genetics and molecular approaches, we show that TBX1 regulates the VEGFR3 and DLL4 genes in brain ECs. In mice, loss of TBX1 causes global brain vascular defects, comprising brain vessel hyperplasia, enhanced angiogenic sprouting and vessel network disorganization. This phenotype is recapitulated in EC-specific Tbx1 conditional mutants and in an EC-only 3-dimensional cell culture system (matrigel), indicating that the brain vascular phenotype is cell autonomous. Furthermore, EC-specific conditional Tbx1 mutants have poorly perfused brain vessels and brain hypoxia, indicating that the expanded vascular network is functionally impaired. In EC-matrigel cultures, a Notch1 agonist is able to partially rescue microtubule hyperbranching induced by TBX1 knockdown. Thus, we have identified a novel transcriptional regulator of angiogenesis that exerts its effect in brain by negatively regulating angiogenesis through the DLL4/Notch1-VEGFR3 regulatory axis. Given the similarity of the phenotypic consequences of TBX1 mutation in humans and mice, this unexpected role of TBX1 in murine brain vascularization should stimulate clinicians to search for brain microvascular anomalies in 22q11.2DS patients and to evaluate whether some of the anatomical and functional brain anomalies in patients may have a microvascular origin.

Challenging the use of adult neuropsychological models for explaining neurodevelopmental disorders: developed versus developing brains

In this paper, I contrast approaches from adult neuropsychology that seek selective, domain-specific deficits with approaches aimed at understanding the dynamics of developmental trajectories in children with genetic disorders. I stress the crucial difference between developed brains damaged in their mature state, and atypically developing brains. I also challenge the search for single genes to explain selective cognitive-level outcomes. Throughout, the paper argues that it is critical to trace cognitive-level deficits back to their basic-level processes in infancy, where genes are likely to exert their early influences, if we are to understand both the impairments and proficiencies displayed in children with neurodevelopmental disorders.

Resting-state networks in adolescents with 22q11.2 deletion syndrome: associations with prodromal symptoms and executive functions

Atypical functional connectivity in the maturing brains of 22q11.2 deletion syndrome (22q11DS) may contribute to the expression of early psychotic symptoms commonly reported by these youths. This study's objective was to examine functional connectivity in cerebral networks at rest (Resting-State Networks; RSNs) and their relationship to symptomatic and neuropsychological characteristics putting them at very high risk factor for developing psychosis. Twenty-seven adolescents with 22q11DS and 33 typically developing control adolescents matched for age, gender and handedness underwent an 8-minute resting state functional MRI session. RSNs identification procedure employed Independent Component Analysis (ICA). We tested for potential group differences in functional connectivity within-networks. Then, we examined relationships between network connectivity and symptomatic/neuropsychological characteristics in the 22q11DS group. A total of nine resting-state networks were identified. Between-group differences suggested both increased and decreased functional connectivity in the 22q11DS group, involving the default-mode, sensorimotor, visuo-spatial, and high level visual networks. Finally, atypical connectivity in the default-mode network, specifically within the left superior frontal gyrus region, correlated with prodromal symptom intensity and neuropsychological performances in the 22q11DS group. The results suggest that atypical functional connectivity may sustain both increased vulnerability to psychosis and characteristic cognitive impairments in 22q11DS.

Association of schizophrenia in 22q11.2 deletion syndrome and gray matter volumetric deficits in the superior temporal gyrus

OBJECTIVE

Individuals with 22q11.2 deletion syndrome are known to be at high risk of developing schizophrenia. Previous imaging studies have provided limited data on the relation of schizophrenia expression in 22q11.2 deletion syndrome to specific regional brain volumetric changes. The authors hypothesized that the main structural brain finding associated with schizophrenia expression in 22q11.2 deletion syndrome, as for schizophrenia in the general population, would be gray matter volumetric deficits, especially in the temporal lobes.

METHOD

MR brain images from 29 patients with 22q11.2 deletion syndrome and schizophrenia and 34 comparison subjects with 22q11.2 deletion syndrome and no history of psychosis were analyzed using a voxel-based morphometry method that also yielded volumes for related region-of-interest analyses. The authors compared data from the two groups using an analysis of covariance model correcting for total intracranial volume, age, sex, IQ, and history of congenital cardiac defects. The false discovery rate threshold was set at 0.05 to account for multiple comparisons.

RESULTS

Voxel-based morphometry analyses identified significant gray matter reductions in the left superior temporal gyrus (Brodmann's area 22) in the schizophrenia group. There were no significant between-group differences in white matter or CSF volumes. Region-of-interest analyses showed significant bilateral gray matter volume reductions in the temporal lobes and superior temporal gyri in the schizophrenia group.

CONCLUSIONS

The structural brain expression of schizophrenia associated with the highly penetrant 22q11.2 deletion involves lower gray matter volumes in temporal lobe regions. These structural MRI findings in a 22q11.2 deletion syndrome form of schizophrenia are consistent with those from studies involving schizophrenia samples from the general population. The results provide further support for 22q11.2 deletion syndrome as a genetic subtype and as a useful neurodevelopmental model of schizophrenia.