Williams syndrome deficits in visual spatial processing linked to GTF2IRD1 and GTF2I on chromosome 7q11.23

Optical coherence tomography angiography findings in Williams-Beuren syndrome

PURPOSE

Williams-Beuren syndrome (WBS) is a rare genetic disease characterized by psychomotor delay, cardiovascular, musculoskeletal, and endocrine problems. Retinal involvement, which is not well characterized, has also been described. The purpose of this cross-sectional study is to describe the characteristics in optical coherence tomography (OCT) and OCT-angiography (OCTA) of patients with WBS.

METHODS

We included patients with WBS confirmed by genetic analysis. The patients underwent OCT (30° × 25°, 61 B-scans) and OCTA (10° × 10° and 20° × 20°) examinations, all centered on the. Data on retinal thickness (total, inner and outer layers) and foveal morphology on OCT and vessel and perfusion density in OCTA (VD and PD, respectively) were collected. These data were compared with an age-matched control group.

RESULTS

22 eyes of 22 patients with WBS (10 females, mean age 31.5 years) were included. Retinal thickness (and specifically inner retinal layers) in OCT was significantly reduced in all sectors (central, parafoveal, and perifoveal) compared to the control group (p < 0.001 in all sectors). Fovea in WBS eyes was broader and shallower than controls. The PD and VD in both 10 and 20 degrees of fields in OCTA was significantly reduced in patients with WBS, in all vascular plexa (all p < 0.001).

CONCLUSIONS

This study is the first to quantify and demonstrate retinal structural and microvascular alterations in patients with WBS. Further studies with longitudinal data will reveal the potential clinical relevance of these alterations.

Neuropsychological Genotype-Phenotype in Patients with Williams Syndrome with Atypical Deletions: A Systematic Review

Williams syndrome (WS) is a neurodevelopmental disorder caused by a microdeletion in the q11.23 region of chromosome 7. Recent case series reports and clinical case studies have suggested that the cognitive, behavioral, emotional, and social profile in WS could depend on the genes involved in the deletion. The objective of this systematic review was to analyze and synthesize the variability of the cognitive and behavioral profile of WS with atypical deletion and its probable relationship with the affected genes. The medical subject headings searched were "Williams syndrome," "genotype," "phenotype," "cognitive profile," and "atypical deletion." The studies included were in English or Spanish, with children and adults, and published between January 2000 and October 2022. Twenty-three studies are reported. The characteristics of the participants, the genes involved, the neuropsychological domains and instruments, and the prevalence of the WS cognitive profile criteria were used for the genotype-phenotype analysis. The genes with a major impact on the cognitive profile of WS were (a) LIMK1 and those belonging to the GTF2I family, the former with a greater influence on visuospatial abilities; (b) GTF2IRD1 and GTF2I, which have an impact on intellectual capacity as well as on visuospatial and social skills; (c) FZD9, BAZ1B, STX1A, and CLIP2, which influence the cognitive profile if other genes are also effected; and (d) GTF2IRD2, which is related to the severity of the effect on visuospatial and social skills, producing a behavioral phenotype like that of the autism spectrum. The review revealed four neuropsychological phenotypes, depending on the genes involved, and established the need for more comprehensive study of the neuropsychological profile of these patients. Based on the results found, we propose a model for the investigation of and clinical approach to the WS neuropsychological phenotype.

Novel ophthalmic findings and deep phenotyping in Williams-Beuren syndrome

BACKGROUND/AIMS

To characterise the ocular manifestations of Williams-Beuren syndrome (WBS) and compare these to patients with isolated elastin mediated supravalvular aortic stenosis (SVAS).

METHODS

Fifty-seven patients with a diagnosis of WBS and five with SVAS underwent comprehensive ophthalmic evaluation at the National Institutes of Health from 2017 to 2020, including best-corrected visual acuity, slit-lamp biomicroscopy, optical biometry, dilated fundus examination, optical coherence tomography and colour fundus imaging.

RESULTS

Mean age of the 57 WBS patients was 20.3 years (range 3-60 years). Best-corrected visual acuity ranged from 20/20 to 20/400 with mean spherical equivalent near plano OU. Twenty-four eyes (21.8%) had an axial length (AL) less than 20.5 mm and 38 eyes (34.5%) had an AL measuring 20.5-22.0 mm. Stellate iris and retinal arteriolar tortuosity were noted in 30 (52.6%) and 51 (89.5%) WBS patients, respectively. Novel retinal findings in WBS included small hypopigmented retinal deposits (OD 29/57, OS 27/57) and broad foveal pit contour (OD 44/55, OS 42/51). Of the five patients with SVAS, none had stellate iris or broad foveal pit contour while 2/5 had retinal arteriolar tortuosity.

CONCLUSION

WBS is a complex multisystem genetic disorder with diverse ophthalmic findings that differ from those seen in isolated elastin mediated SVAS. These results suggest other genes within the WBS critical region, aside from ELN, may be involved in observed ocular phenotypes and perhaps broader ocular development. Furthermore, retinal arteriolar tortuosity may provide future insight into systemic vascular findings in WBS.

Fluorescence in situ hybridization (FISH) as an irreplaceable diagnostic tool for Williams-Beuren syndrome in developing countries: a literature review

OBJECTIVE

The aim of this study was to sum up and characterize all Williams-Beuren syndrome cases diagnosed by fluorescence in situ hybridization (FISH) since its implementation, as well as to discuss FISH as a cost-effective methodology in developing countries.

DATA SOURCE

From January 1986 to January 2022, articles were selected using the databases in PubMed (Medline) and SciELO. The following terms were used: Williams syndrome and In Situ Hybridization, Fluorescence. Inclusion criteria included Williams-Beuren syndrome cases diagnosed by FISH with a stratified phenotype of each patient. Only studies written in English, Spanish, and Portuguese were included. Studies with overlapping syndromes or genetic conditions were excluded.

DATA SYNTHESIS

After screening, 64 articles were included. A total of 205 individuals with Williams-Beuren syndrome diagnosed by FISH were included and further analyzed. Cardiovascular malformations were the most frequent finding (85.4%). Supravalvular aortic stenosis (62.4%) and pulmonary stenosis (30.7%) were the main cardiac alterations described.

CONCLUSIONS

Our literature review reinforces that cardiac features may be the key to early diagnosis in Williams-Beuren syndrome patients. In addition, FISH may be the best diagnostic tool for developing nations that have limited access to new technologic resources.

Innate frequency-discrimination hyperacuity in Williams-Beuren syndrome mice

Williams-Beuren syndrome (WBS) is a rare disorder caused by hemizygous microdeletion of ∼27 contiguous genes. Despite neurodevelopmental and cognitive deficits, individuals with WBS have spared or enhanced musical and auditory abilities, potentially offering an insight into the genetic basis of auditory perception. Here, we report that the mouse models of WBS have innately enhanced frequency-discrimination acuity and improved frequency coding in the auditory cortex (ACx). Chemogenetic rescue showed frequency-discrimination hyperacuity is caused by hyperexcitable interneurons in the ACx. Haploinsufficiency of one WBS gene, Gtf2ird1, replicated WBS phenotypes by downregulating the neuropeptide receptor VIPR1. VIPR1 is reduced in the ACx of individuals with WBS and in the cerebral organoids derived from human induced pluripotent stem cells with the WBS microdeletion. Vipr1 deletion or overexpression in ACx interneurons mimicked or reversed, respectively, the cellular and behavioral phenotypes of WBS mice. Thus, the Gtf2ird1-Vipr1 mechanism in ACx interneurons may underlie the superior auditory acuity in WBS.

Neuropsychological intervention in attention and visuospatial skills in two patients with Williams syndrome with different types of genetic deletion

Williams Syndrome (WS) is a neurodevelopmental disorder with a distinctive physical, cognitive, and behavioral profile caused by a microdeletion in the q11.23 region of chromosome 7. The neuropsychological profile of WS is characterized by intellectual disability, hypersociability, and deficits, especially in attention and visuospatial skills. Our objective was to assess the effectiveness of a neuropsychological intervention program in attention and visuospatial skills in two patients with WS (aged 7 and 13 years old) with different types of deletion (1.5 and 1.8 Mb). Cognitive, behavioral, and adaptive abilities were evaluated through various neuropsychological tests and scales; the neuropsychological intervention program was subsequently applied, and we assessed its effectiveness. Both patients initially presented significant deficits in attention and visuospatial skills. After the program, we found improvements in attention and visuospatial skills. In addition, both patients had significant clinical advances and changes in adaptive behaviors (social and self-care). These findings suggest that this intervention program could improve attention processes, visuospatial skills, and some aspects of adaptive behavior in patients with WS, regardless of deletion size. Although the sample was small, limiting the generalizability of the results, we believe this program could be a helpful resource for professionals working with individuals with WS.

Transcriptome analysis reveals sexual disparities in gene expression in rat brain microvessels

Sex is an important determinant of brain microvessels (MVs) function and susceptibility to cerebrovascular and neurological diseases, but underlying mechanisms are unclear. Using high throughput RNA sequencing analysis, we examined differentially expressed (DE) genes in brain MVs from young, male, and female rats. Bioinformatics analysis of the 23,786 identified genes indicates that 298 (1.2%) genes were DE using False Discovery Rate criteria (FDR; p < 0.05), of which 119 (40%) and 179 (60%) genes were abundantly expressed in male and female MVs, respectively. Nucleic acid binding, enzyme modulator, and transcription factor were the top three DE genes, which were more highly expressed in male than female MVs. Synthesis of glycosylphosphatidylinositol (GPI), biosynthesis of GPI-anchored proteins, steroid and cholesterol synthesis, were the top three significantly enriched canonical pathways in male MVs. In contrast, respiratory chain, ribosome, and 3 ́-UTR-mediated translational regulation were the top three enriched canonical pathways in female MVs. Different gene functions of MVs were validated by proteomic analysis and western blotting. Our novel findings reveal major sex disparities in gene expression and canonical pathways of MVs and these differences provide a foundation to study the underlying mechanisms and consequences of sex-dependent differences in cerebrovascular and other neurological diseases.

Functional variant rs17525453 within RAB35 gene promoter is possibly associated with increased risk of Parkinson's disease in Taiwanese population

Our previous study suggests that upregulated RAB35 is implicated in etiology of Parkinson's disease (PD). We hypothesized that upregulated RAB35 results from single nucleotide polymorphisms (SNPs) in RAB35 gene promoter. We identified SNPs within RAB35 gene promoter by analyzing DNA samples of discovery cohort and validation cohort. SNP rs17525453 within RAB35 gene promoter (T>C at position of -66) was significantly associated with idiopathic PD patients. Compared to normal controls, sporadic PD patients had higher C allele frequency. CC and CT genotype significantly increased risk of PD compared with TT genotype. SNP rs17525453 within RAB35 gene promoter leads to formation of transcription factor TFII-I binding site. Results of EMSA and supershift assay indicated that TFII-I binds to rs17525453 sequence of RAB35 gene promoter. Luciferase reporter assays showed that rs17525453 variant of RAB35 gene promoter possesses an augmented transcriptional activity. Our results suggest that functional variant rs17525453 within RAB35 gene promoter is likely to enhance transcriptional activity and upregulate RAB35 protein, which could lead to increased risk of PD in Taiwanese population.

Williams syndrome

Williams syndrome (WS) is a relatively rare microdeletion disorder that occurs in as many as 1:7,500 individuals. WS arises due to the mispairing of low-copy DNA repetitive elements at meiosis. The deletion size is similar across most individuals with WS and leads to the loss of one copy of 25-27 genes on chromosome 7q11.23. The resulting unique disorder affects multiple systems, with cardinal features including but not limited to cardiovascular disease (characteristically stenosis of the great arteries and most notably supravalvar aortic stenosis), a distinctive craniofacial appearance, and a specific cognitive and behavioural profile that includes intellectual disability and hypersociability. Genotype-phenotype evidence is strongest for ELN, the gene encoding elastin, which is responsible for the vascular and connective tissue features of WS, and for the transcription factor genes GTF2I and GTF2IRD1, which are known to affect intellectual ability, social functioning and anxiety. Mounting evidence also ascribes phenotypic consequences to the deletion of BAZ1B, LIMK1, STX1A and MLXIPL, but more work is needed to understand the mechanism by which these deletions contribute to clinical outcomes. The age of diagnosis has fallen in regions of the world where technological advances, such as chromosomal microarray, enable clinicians to make the diagnosis of WS without formally suspecting it, allowing earlier intervention by medical and developmental specialists. Phenotypic variability is considerable for all cardinal features of WS but the specific sources of this variability remain unknown. Further investigation to identify the factors responsible for these differences may lead to mechanism-based rather than symptom-based therapies and should therefore be a high research priority.

Atypical 7q11.23 deletions excluding ELN gene result in Williams-Beuren syndrome craniofacial features and neurocognitive profile

Williams-Beurens syndrome (WBS) is a rare genetic disorder caused by a recurrent 7q11.23 microdeletion. Clinical characteristics include typical facial dysmorphisms, weakness of connective tissue, short stature, mild to moderate intellectual disability and distinct behavioral phenotype. Cardiovascular diseases are common due to haploinsufficiency of ELN gene. A few cases of larger or smaller deletions have been reported spanning towards the centromeric or the telomeric regions, most of which included ELN gene. We report on three patients from two unrelated families, presenting with distinctive WBS features, harboring an atypical distal deletion excluding ELN gene. Our study supports a critical role of CLIP2, GTF2IRD1, and GTF2I gene in the WBS neurobehavioral profile and in craniofacial features, highlights a possible role of HIP1 in the autism spectrum disorder, and delineates a subgroup of WBS individuals with an atypical distal deletion not associated to an increased risk of cardiovascular defects.

An Exploration of Social Cognition in Children with Different Degrees of Genetic Deletion in Williams Syndrome

An explanation for the social dysfunction observed in Williams syndrome may be deficits in social cognition. This study explored aspects of social cognition in children with Williams syndrome with different genotypes. The 12 participants included one with a 1.1 Mb deletion that retained the GTF2IRD1, GTF2I, and GTF2IRD2 genes, seven with a 1.5 Mb deletion that preserved the GTF2IRD2 gene, and four with a 1.8 Mb deletion with loss of all three genes. The participant retaining all three genes was found to have better performance on social judgment and first-order theory of mind tasks than the group with loss of all three genes. These results may reflect the influence of the GTF2I gene family on social cognition in Williams syndrome.

Gtf2i and Gtf2ird1 mutation do not account for the full phenotypic effect of the Williams syndrome critical region in mouse models

Williams syndrome (WS) is a neurodevelopmental disorder caused by a 1.5-1.8 Mbp deletion on chromosome 7q11.23, affecting the copy number of 26-28 genes. Phenotypes of WS include cardiovascular problems, craniofacial dysmorphology, deficits in visual-spatial cognition and a characteristic hypersocial personality. There are still no genes in the region that have been consistently linked to the cognitive and behavioral phenotypes, although human studies and mouse models have led to the current hypothesis that the general transcription factor 2 I family of genes, GTF2I and GTF2IRD1, are responsible. Here we test the hypothesis that these two transcription factors are sufficient to reproduce the phenotypes that are caused by deletion of the WS critical region (WSCR). We compare a new mouse model with loss of function mutations in both Gtf2i and Gtf2ird1 to an established mouse model lacking the complete WSCR. We show that the complete deletion (CD) model has deficits across several behavioral domains including social communication, motor functioning and conditioned fear that are not explained by loss of function mutations in Gtf2i and Gtf2ird1. Furthermore, transcriptome profiling of the hippocampus shows changes in synaptic genes in the CD model that are not seen in the double mutants. Thus, we have thoroughly defined a set of molecular and behavioral consequences of complete WSCR deletion and shown that genes or combinations of genes beyond Gtf2i and Gtf2ird1 are necessary to produce these phenotypic effects.

A comparative study of the neuropsychiatric and neurocognitive phenotype in two microdeletion syndromes: Velocardiofacial (22q11.2 deletion) and Williams (7q11.23 deletion) syndromes

Purpose:

22q11.2 deletion syndrome (22q11.2DS) and Williams syndrome (WS) are common neurogenetic microdeletion syndromes. The aim of the present study was to compare the neuropsychiatric and neurocognitive phenotypes of 22q11.2DS and WS.

Methods:

Forty-five individuals with 22q11.2DS, 24 with WS, 22 with idiopathic developmental disability (DD) and 22 typically developing (TD) controls were compared for the rates of psychiatric disorders as well as cognitive executive and visuospatial functions.

Results:

We found that while anxiety, mood and disruptive disorders had an equally high prevalence among individuals with 22q11.2DS, WS and DDs, the 22q11.2DS group had the highest rates of psychotic disorders and the WS group had the highest rates of specific phobia. We also found that the WS group demonstrated more severe impairments in both executive and visuospatial functions than the other groups. WS and 22q11.2DS subjects had worse Performance-IQ than Verbal-IQ, a feature typical of non-verbal learning disorders.

Conclusion:

These findings offer a wide perspective on unique versus common phenotypes in 22q11.2DS and WS.

Cognitive, Behavioral, and Adaptive Profiles in Williams Syndrome With and Without Loss of GTF2IRD2

Williams syndrome (WS) is a neurodevelopmental disorder that results from a heterozygous microdeletion on chromosome 7q11.23. Most of the time, the affected region contains ~1.5 Mb of sequence encoding approximately 24 genes. Some 5-8% of patients with WS have a deletion exceeding 1.8 Mb, thereby affecting two additional genes, including GTF2IRD2. Currently, there is no consensus regarding the implications of GTF2IRD2 loss for the neuropsychological phenotype of WS patients.

OBJECTIVES

The present study aimed to identify the role of GTF2IRD2 in the cognitive, behavioral, and adaptive profile of WS patients.

METHODS

Twelve patients diagnosed with WS participated, four with GTF2IRD2 deletion (atypical WS group), and eight without this deletion (typical WS group). The age range of both groups was 7-18 years old. Each patient's 7q11.23 deletion scope was determined by chromosomal microarray analysis. Cognitive, behavioral, and adaptive abilities were assessed with a battery of neuropsychological tests.

RESULTS

Compared with the typical WS group, the atypical WS patients with GTF2IRD2 deletion had more impaired visuospatial abilities and more significant behavioral problems, mainly related to the construct of social cognition.

CONCLUSIONS

These findings provide new evidence regarding the influence of the GTF2IRD2 gene on the severity of behavioral symptoms of WS related to social cognition and certain visuospatial abilities. (JINS, 2018, 24, 896-904).

A Different Brain: Anomalies of Functional and Structural Connections in Williams Syndrome

We describe the results of a functional and structural brain connectivity analysis comparing a homogeneous group of 10 young adults with Williams Syndrome (WS; 3 females, age 20. 7 ± 3.7 years, age range 17.4–28.7 years) to a group of 18 controls of similar age (3 females, age 23.9 ± 4.4 years, age range 16.8–30.2), with the aim to increase knowledge of the structure – function relationship in WS. Subjects underwent a 3T brain MRI exam including anatomical, functional (resting state) and structural (diffusion MRI) sequences. We found convergent anomalies in structural and functional connectivity in the WS group. Altered Fractional Anisotropy (FA) values in parieto-occipital regions were associated with increased connectivity in the antero-posterior pathways linking parieto-occipital with frontal regions. The analysis of resting state data showed altered functional connectivity in the WS group in main brain networks (default mode, executive control and dorsal attention, sensori-motor, fronto—parietal, ventral stream). The combined analysis of functional and structural connectivity displayed a different pattern in the two groups: in controls the highest agreement was found in frontal and visual areas, whereas in WS patients in posterior regions (parieto-occipital and temporal areas). These preliminary findings may reflect an altered “wiring” of the brain in WS, which can be driven by hyper-connectivity of the posterior regions as opposed to disrupted connectivity in the anterior areas, supporting the hypothesis that a different brain (organization) could be associated with a different (organization of) behavior in Williams Syndrome.

The contribution of GTF2I haploinsufficiency to Williams syndrome

Williams syndrome (WS) is a neurodevelopmental disorder involving hemideletion of as many as 26-28 genes, resulting in a constellation of unique physical, cognitive and behavior phenotypes. The haploinsufficiency effect of each gene has been studied and correlated with phenotype(s) using several models including WS subjects, animal models, and peripheral cell lines. However, links for most of the genes to WS phenotypes remains unclear. Among those genes, general transcription factor 2I (GTF2I) is of particular interest as its haploinsufficiency is possibly associated with hypersociability in WS. Here, we describe studies of atypical WS cases as well as mouse models focusing on GTF2I that support a role for this protein in the neurocognitive and behavioral profiles of WS individuals. We also review collective studies on diverse molecular functions of GTF2I that may provide mechanistic explanation for phenotypes recently reported in our relevant cellular model, namely WS induced pluripotent stem cell (iPSC)-derived neurons. Finally, in light of the progress in gene-manipulating approaches, we suggest their uses in revealing the neural functions of GTF2I in the context of WS.

Pathophysiology of TFII-I: Old Guard Wearing New Hats

The biochemical properties of the signal-induced multifunctional transcription factor II-I (TFII-I) indicate that it is involved in a variety of gene regulatory processes. Although gene ablation in murine models and cell-based assays show that it is encoded by an essential gene, GTF2I/Gtf2i, its physiologic role in human disorders was relatively unknown until recently. Novel studies show that it is involved in an array of human diseases including neurocognitive disorders, systemic lupus erythematosus (SLE), and cancer. Here I bring together these diverse observations to illustrate its multiple pathophysiologic functions and further conjecture on how these could be related to its known biochemical properties. I expect that a better understanding of these 'structure-function' relationships would lead to future diagnostic and/or therapeutic potential.

High-resolution single nucleotide polymorphism arrays identified an atypical microdeletion of the Williams-Beuren syndrome interval in a patient presenting with a different phenotype

The present study aimed to identify the mutation causing an atypical syndrome. High-resolution single nucleotide polymorphism (SNP) arrays are considered to be a major detection method for submicroscopic chromosomal rearrangements smaller than 5 Mb in size. Genomic DNA samples of the patient and his parents were converted to a final concentration of 50 ng/ml. The Illumina BeadScan genotyping system and the HumanOmni1‑Quad Chip were employed to obtain the signal intensities of SNP probes. The patient presented with congenital heart disease, autism, mental retardation, growth retardation, hypercalcemia, nephroliths and cleft palate. The karyotypes of the patient and his parents were normal. The present study employed high‑resolution SNP arrays to analyze the whole genome for copy number variations (CNVs). A total of 309 CNVs were discovered. A de novo 1.5 Mb gain of chromosome 7q11.23 (Chr7: 72,357,322‑73,856,472) was identified following exclusion of CNVs presented in the Database of Genomic Variants. In conclusion, to the best of our knowledge, the current study describes the first case of a patient presenting with Williams‑Beuren syndrome alongside supravalvular aortic stenosis, autism and cleft palate, and identifies an atypical deletion at 7q11.23.

Disparities in visuo-spatial constructive abilities in Williams syndrome patients with typical deletion on chromosome 7q11.23

BACKGROUND

Williams syndrome (WS) is known for its uneven cognitive abilities, especially the difficulty in visuo-spatial cognition, though there are some inter-individual phenotypic differences. It has been proposed that the difficulty in visuo-spatial cognition of WS patients can be attributed to a haploinsufficiency of some genes located on the deleted region in 7q11.23, based on an examination of atypical deletions identified in WS patients with atypical cognitive deficits. According to this hypothesis, the inter-individual differences in visuo-spatial cognitive ability arise from variations in deletion.

METHODS

We investigated whether there were inter-individual differences in the visuo-spatial constructive abilities of five unrelated WS patients with the typical deletion on chromosome 7q11.23 that includes the candidate genes contributing visuo-spatial difficulty in WS patients. We used tests with three-dimensional factors such as Benton's three-dimensional block construction test, which are considered to be more sensitive than those with only two-dimensional factors.

RESULTS

There were diverse inter-individual differences in the visuo-spatial constructive abilities among the present participants who shared the same typical genomic deletion of WS. One of the participants showed almost equivalent performances to typically developing adults in those tests.

CONCLUSION

In the present study, we found a wide range of cognitive abilities in visuo-spatial construction even among the patients with a common deletion pattern of WS. The findings suggest that attributing differences in the phenotypes entirely to genetic factors such as an atypical deletion may not be always correct.

Haploinsufficiency of BAZ1B contributes to Williams syndrome through transcriptional dysregulation of neurodevelopmental pathways

Williams syndrome (WS) is a neurodevelopmental disorder caused by a genomic deletion of ∼28 genes that results in a cognitive and behavioral profile marked by overall intellectual impairment with relative strength in expressive language and hypersocial behavior. Advancements in protocols for neuron differentiation from induced pluripotent stem cells allowed us to elucidate the molecular circuitry underpinning the ontogeny of WS. In patient-derived stem cells and neurons, we determined the expression profile of the Williams-Beuren syndrome critical region-deleted genes and the genome-wide transcriptional consequences of the hemizygous genomic microdeletion at chromosome 7q11.23. Derived neurons displayed disease-relevant hallmarks and indicated novel aberrant pathways in WS neurons including over-activated Wnt signaling accompanying an incomplete neurogenic commitment. We show that haploinsufficiency of the ATP-dependent chromatin remodeler, BAZ1B, which is deleted in WS, significantly contributes to this differentiation defect. Chromatin-immunoprecipitation (ChIP-seq) revealed BAZ1B target gene functions are enriched for neurogenesis, neuron differentiation and disease-relevant phenotypes. BAZ1B haploinsufficiency caused widespread gene expression changes in neural progenitor cells, and together with BAZ1B ChIP-seq target genes, explained 42% of the transcriptional dysregulation in WS neurons. BAZ1B contributes to regulating the balance between neural precursor self-renewal and differentiation and the differentiation defect caused by BAZ1B haploinsufficiency can be rescued by mitigating over-active Wnt signaling in neural stem cells. Altogether, these results reveal a pivotal role for BAZ1B in neurodevelopment and implicate its haploinsufficiency as a likely contributor to the neurological phenotypes in WS.

Rare genomic rearrangement in a boy with Williams-Beuren syndrome associated to XYY syndrome and intriguing behavior

Williams-Beuren syndrome (WBS) is caused by a hemizygous contiguous gene microdeletion of 1.55-1.84 Mb at 7q11.23 region. Approximately, 28 genes have been shown to contribute to classical phenotype of SWB with presence of dysmorphic facial features, supravalvular aortic stenosis (SVAS), intellectual disability, and overfriendliness. With the use of Microarray-based comparative genomic hybridization and other molecular cytogenetic techniques, is possible define with more accuracy partial or atypical deletion and refine the genotype-phenotype correlation. Here, we report on a rare genomic structural rearrangement in a boy with atypical deletion in 7q11.23 and XYY syndrome with characteristic clinical signs, but not sufficient for the diagnosis of WBS. Cytogenetic analysis of G-banding showed a karyotype 47,XYY. Analysis of DNA with the technique of MLPA (Multiplex Ligation-dependent Probe Amplification) using kits a combination of kits (P064, P036, P070, and P029) identified an atypical deletion on 7q11.23. In addition, high resolution SNP Oligonucleotide Microarray Analysis (SNP-array) confirmed the alterations found by MLPA and revealed others pathogenic CNVs, in the chromosomes 7 and X. The present report demonstrates an association not yet described in literature, between Williams-Beuren syndrome and 47,XYY. The identification of atypical deletion in 7q11.23 concomitant to additional pathogenic CNVs in others genomic regions allows a better comprehension of clinical consequences of atypical genomic rearrangements.

A Novel Recurrent Breakpoint Responsible for Rearrangements in the Williams-Beuren Region

Copy number variants (CNVs) of the Williams-Beuren syndrome (WBS) 7q11.23 region are responsible for neurodevelopmental disorders with multisystem involvement and variable expressivity. We found 2 patients with a deletion and 1 patient with a duplication in this region sharing a common breakpoint located between the LIMK1 and EIF4H(WBSCR1) genes. One patient had a WBS phenotype, although testing with a commercially available FISH assay was negative for the deletion. A further test using array CGH showed an atypical WBS region deletion. The second patient showed global developmental delay, speech delay and poor motor skills with a deletion outside the WBS region. The third patient had manifestations compatible with an autism spectrum disorder showing a duplication in the WBS region. Our findings point to the existence of a previously unrecognized recurrent breakpoint responsible for rearrangements in the WBS region. Given that most commercial FISH assays include probes flanking this novel breakpoint, further testing with array CGH should be performed in patients with WBS and negative FISH results.

7q11.23 dosage-dependent dysregulation in human pluripotent stem cells affects transcriptional programs in disease-relevant lineages

Cell reprogramming promises to make characterization of the impact of human genetic variation on health and disease experimentally tractable by enabling the bridging of genotypes to phenotypes in developmentally relevant human cell lineages. Here we apply this paradigm to two disorders caused by symmetrical copy number variations of 7q11.23, which display a striking combination of shared and symmetrically opposite phenotypes--Williams-Beuren syndrome and 7q-microduplication syndrome. Through analysis of transgene-free patient-derived induced pluripotent stem cells and their differentiated derivatives, we find that 7q11.23 dosage imbalance disrupts transcriptional circuits in disease-relevant pathways beginning in the pluripotent state. These alterations are then selectively amplified upon differentiation of the pluripotent cells into disease-relevant lineages. A considerable proportion of this transcriptional dysregulation is specifically caused by dosage imbalances in GTF2I, which encodes a key transcription factor at 7q11.23 that is associated with the LSD1 repressive chromatin complex and silences its dosage-sensitive targets.

Challenges in clinical diagnosis of williams-beuren syndrome in sub-saharan africans: case reports from cameroon

Williams-Beuren syndrome (WBS) is a rare neurodevelopmental condition caused by a recurrent chromosomal microdeletion involving about 28 contiguous genes at 7q11.23. Most patients display a specific congenital heart defect, characteristic facial features, a particular behavior, and intellectual disability. Cases from sub-Saharan Africa have been seldom reported. The present study describes 3 Cameroonian patients affected by WBS, aged 19 months, 13 and 14 years, in whom the diagnosis was confirmed by fluorescent in situ hybridization (FISH) and comparative genomic hybridization (CGH). The first patient presented with a congenital heart defect, the second and third with learning difficulties as well as developmental and behavioral issues. In the latter 2 cases, the facial phenotypes were similar to those of the unaffected population with the same ethnic background. However, the cardiovascular anomalies and friendly behavioral attitudes led to suspicion of WBS. FISH revealed the deletion of the WBS critical region in the first patient, and array-CGH detected a heterozygous ∼1.4-Mb deletion in the 7q11.23 region in the second and third patient. This preliminary report suggests that for sub-Saharan Africans clinical suspicion of WBS could be mostly based on behavioral phenotype and structural heart defects, and less on the classical facial dysmorphic signs.

Mapping genetically controlled neural circuits of social behavior and visuo-motor integration by a preliminary examination of atypical deletions with Williams syndrome

In this study of eight rare atypical deletion cases with Williams-Beuren syndrome (WS; also known as 7q11.23 deletion syndrome) consisting of three different patterns of deletions, compared to typical WS and typically developing (TD) individuals, we show preliminary evidence of dissociable genetic contributions to brain structure and human cognition. Univariate and multivariate pattern classification results of morphometric brain patterns complemented by behavior implicate a possible role for the chromosomal region that includes: 1) GTF2I/GTF2IRD1 in visuo-spatial/motor integration, intraparietal as well as overall gray matter structures, 2) the region spanning ABHD11 through RFC2 including LIMK1, in social cognition, in particular approachability, as well as orbitofrontal, amygdala and fusiform anatomy, and 3) the regions including STX1A, and/or CYLN2 in overall white matter structure. This knowledge contributes to our understanding of the role of genetics on human brain structure, cognition and pathophysiology of altered cognition in WS. The current study builds on ongoing research designed to characterize the impact of multiple genes, gene-gene interactions and changes in gene expression on the human brain.

Genetic contributions to visuospatial cognition in Williams syndrome: insights from two contrasting partial deletion patients

Background

Williams syndrome (WS) is a rare neurodevelopmental disorder arising from a hemizygotic deletion of approximately 27 genes on chromosome 7, at locus 7q11.23. WS is characterised by an uneven cognitive profile, with serious deficits in visuospatial tasks in comparison to relatively proficient performance in some other cognitive domains such as language and face processing. Individuals with partial genetic deletions within the WS critical region (WSCR) have provided insights into the contribution of specific genes to this complex phenotype. However, the combinatorial effects of different genes remain elusive.

Methods

We report on visuospatial cognition in two individuals with contrasting partial deletions in the WSCR: one female (HR), aged 11 years 9 months, with haploinsufficiency for 24 of the WS genes (up to GTF2IRD1), and one male (JB), aged 14 years 2 months, with the three most telomeric genes within the WSCR deleted, or partially deleted.

Results

Our in-depth phenotyping of the visuospatial domain from table-top psychometric, and small- and large-scale experimental tasks reveal a profile in HR in line with typically developing controls, albeit with some atypical features. These data are contrasted with patient JB’s atypical profile of strengths and weaknesses across the visuospatial domain, as well as with more substantial visuospatial deficits in individuals with the full WS deletion.

Conclusions

Our findings point to the contribution of specific genes to spatial processing difficulties associated with WS, highlighting the multifaceted nature of spatial cognition and the divergent effects of genetic deletions within the WSCR on different components of visuospatial ability. The importance of general transcription factors at the telomeric end of the WSCR, and their combinatorial effects on the WS visuospatial phenotype are also discussed.

Presence of autism, hyperserotonemia, and severe expressive language impairment in Williams-Beuren syndrome

BACKGROUND

Deletion of the Williams-Beuren syndrome (WBS) critical region (WBSCR), at 7q11.23, causes a developmental disorder commonly characterized by hypersociability and excessive talkativeness and often considered the opposite behavioral phenotype to autism. Duplication of the WBSCR leads to severe delay in expressive language. Gene-dosage effects on language development at 7q11.23 have been hypothesized.

METHODS

Molecular characterization of the WBSCR was performed by fluorescence in situ hybridization and high-resolution single-nucleotide polymorphism array in two individuals with severe autism enrolled in a genetic study of autism who showed typical WBS facial dysmorphism on systematic clinical genetic examination. The serotonin transporter promoter polymorphism (5-HTTLPR, locus SLC6A4) was genotyped. Platelet serotonin levels and urinary 6-sulfatoxymelatonin excretion were measured. Behavioral and cognitive phenotypes were examined.

RESULTS

The two patients had common WBSCR deletions between proximal and medial low copy repeat clusters, met diagnostic criteria for autism and displayed severe impairment in communication, including a total absence of expressive speech. Both patients carried the 5-HTTLPR ss genotype and exhibited platelet hyperserotonemia and low melatonin production.

CONCLUSIONS

Our observations indicate that behaviors and neurochemical phenotypes typically associated with autism can occur in patients with common WBSCR deletions. The results raise intriguing questions about phenotypic heterogeneity in WBS and regarding genetic and/or environmental factors interacting with specific genes at 7q11.23 sensitive to dosage alterations that can influence the development of social communication skills. Thus, the influence of WBSCR genes on social communication expression might be dramatically modified by other genes, such as 5-HTTLPR, known to influence the severity of social communication impairments in autism, or by environmental factors, such as hyperserotonemia, given that hyperserotonemia is found in WBS associated with autism but not in WBS without autism. In this regard, WBS provides a potentially fruitful model with which to develop integrated genetic, cognitive, behavioral and neurochemical approaches to study genotype-phenotype correlations, possible gene-environment interactions and genetic background effects. The results underscore the importance of considering careful clinical and molecular genetic examination of individuals diagnosed with autism.

Smaller and larger deletions of the Williams Beuren syndrome region implicate genes involved in mild facial phenotype, epilepsy and autistic traits

Williams Beuren syndrome (WBS) is a multisystemic disorder caused by a hemizygous deletion of 1.5 Mb on chromosome 7q11.23 spanning 28 genes. A few patients with larger and smaller WBS deletion have been reported. They show clinical features that vary between isolated SVAS to the full spectrum of WBS phenotype, associated with epilepsy or autism spectrum behavior. Here we describe four patients with atypical WBS 7q11.23 deletions. Two carry ~3.5 Mb larger deletion towards the telomere that includes Huntingtin-interacting protein 1 (HIP1) and tyrosine 3-monooxygenase/tryptophan 5-monooxigenase activation protein gamma (YWHAG) genes. Other two carry a shorter deletion of ~1.2 Mb at centromeric side that excludes the distal WBS genes BAZ1B and FZD9. Along with previously reported cases, genotype-phenotype correlation in the patients described here further suggests that haploinsufficiency of HIP1 and YWHAG might cause the severe neurological and neuropsychological deficits including epilepsy and autistic traits, and that the preservation of BAZ1B and FZD9 genes may be related to mild facial features and moderate neuropsychological deficits. This report highlights the importance to characterize additional patients with 7q11.23 atypical deletions comparing neuropsychological and clinical features between these individuals to shed light on the pathogenic role of genes within and flanking the WBS region.

A 1.3-mb 7q11.23 atypical deletion identified in a cohort of patients with williams-beuren syndrome

Williams-Beuren syndrome is a rare multisystem neurodevelopmental disorder caused by a 1.55-1.84-Mb hemizygous deletion on chromosome 7q11.23. The classical phenotype consists of characteristic facial features, supravalvular aortic stenosis, intellectual disability, overfriendliness, and visuospatial impairment. So far, 26-28 genes have been shown to contribute to the multisystem phenotype associated with Williams-Beuren syndrome. Among them, haploinsufficiency of the ELN gene has been shown to cause the cardiovascular anomalies. Identification of patients with atypical deletions has provided valuable information for genotype-phenotype correlation, in which other genes such as LIMK1,CLIP2, GTF2IRD1, or GTF2I have been correlated with specific cognitive profiles or craniofacial features. Here, we report the clinical and molecular characteristics of a patient with an atypical deletion that does not include the GTF2I gene and only partially includes the GTF2IRD1 gene.

Genetic mapping of brain plasticity across development in Williams syndrome: ERP markers of face and language processing

In Williams Syndrome (WS), a known genetic deletion results in atypical brain function with strengths in face and language processing. We examined how genetic influences on brain activity change with development. In three studies, event-related potentials (ERPs) from large samples of children, adolescents, and adults with the full genetic deletion for WS were compared to typically developing controls, and two adults with partial deletions for WS. Studies 1 and 2 identified ERP markers of brain plasticity in WS across development. Study 3 suggested that, in adults with partial deletions for WS, specific genes may be differentially implicated in face and language processing.

SUMOylation of GTF2IRD1 regulates protein partner interactions and ubiquitin-mediated degradation

GTF2IRD1 is one of the genes implicated in Williams-Beuren syndrome, a disease caused by haploinsufficiency of certain dosage-sensitive genes within a hemizygous microdeletion of chromosome 7. GTF2IRD1 is a prime candidate for some of the major features of the disease, presumably caused by abnormally reduced abundance of this putative transcriptional repressor protein. GTF2IRD1 has been shown to interact with the E3 SUMO ligase PIASxβ, but the significance of this relationship is largely unexplored. Here, we demonstrate that GTF2IRD1 can be SUMOylated by the SUMO E2 ligase UBC9 and the level of SUMOylation is enhanced by PIASxβ. A major SUMOylation site was mapped to lysine 495 within a conserved SUMO consensus motif. SUMOylation of GTF2IRD1 alters the affinity of the protein for binding partners that contain SUMO-interacting motifs, including a novel family member of the HDAC repressor complex, ZMYM5, and PIASxβ itself. In addition, we show that GTF2IRD1 is targeted for ubiquitination and proteasomal degradation. Cross regulation by SUMOylation modulates this process, thus potentially regulating the level of GTF2IRD1 protein in the cell. These findings, concerning post-translational control over the activity and stability of GTF2IRD1, together with previous work showing how GTF2IRD1 directly regulates its own transcription levels suggest an evolutionary requirement for fine control over GTF2IRD1 activity in the cell.

Oxytocin and vasopressin are dysregulated in Williams Syndrome, a genetic disorder affecting social behavior

The molecular and neural mechanisms regulating human social-emotional behaviors are fundamentally important but largely unknown; unraveling these requires a genetic systems neuroscience analysis of human models. Williams Syndrome (WS), a condition caused by deletion of ∼28 genes, is associated with a gregarious personality, strong drive to approach strangers, difficult peer interactions, and attraction to music. WS provides a unique opportunity to identify endogenous human gene-behavior mechanisms. Social neuropeptides including oxytocin (OT) and arginine vasopressin (AVP) regulate reproductive and social behaviors in mammals, and we reasoned that these might mediate the features of WS. Here we established blood levels of OT and AVP in WS and controls at baseline, and at multiple timepoints following a positive emotional intervention (music), and a negative physical stressor (cold). We also related these levels to standardized indices of social behavior. Results revealed significantly higher median levels of OT in WS versus controls at baseline, with a less marked increase in AVP. Further, in WS, OT and AVP increased in response to music and to cold, with greater variability and an amplified peak release compared to controls. In WS, baseline OT but not AVP, was correlated positively with approach, but negatively with adaptive social behaviors. These results indicate that WS deleted genes perturb hypothalamic-pituitary release not only of OT but also of AVP, implicating more complex neuropeptide circuitry for WS features and providing evidence for their roles in endogenous regulation of human social behavior. The data suggest a possible biological basis for amygdalar involvement, for increased anxiety, and for the paradox of increased approach but poor social relationships in WS. They also offer insight for translating genetic and neuroendocrine knowledge into treatments for disorders of social behavior.

The contribution of CLIP2 haploinsufficiency to the clinical manifestations of the Williams-Beuren syndrome

Williams-Beuren syndrome is a rare contiguous gene syndrome, characterized by intellectual disability, facial dysmorphisms, connective-tissue abnormalities, cardiac defects, structural brain abnormalities, and transient infantile hypercalcemia. Genes lying telomeric to RFC2, including CLIP2, GTF2I and GTF2IRD1, are currently thought to be the most likely major contributors to the typical Williams syndrome cognitive profile, characterized by a better-than-expected auditory rote-memory ability, a relative sparing of language capabilities, and a severe visual-spatial constructive impairment. Atypical deletions in the region have helped to establish genotype-phenotype correlations. So far, however, hardly any deletions affecting only a single gene in the disease region have been described. We present here two healthy siblings with a pure, hemizygous deletion of CLIP2. A putative role in the cognitive and behavioral abnormalities seen in Williams-Beuren patients has been suggested for this gene on the basis of observations in a knock-out mouse model. The presented siblings did not show any of the clinical features associated with the syndrome. Cognitive testing showed an average IQ for both and no indication of the Williams syndrome cognitive profile. This shows that CLIP2 haploinsufficiency by itself does not lead to the physical or cognitive characteristics of the Williams-Beuren syndrome, nor does it lead to the Williams syndrome cognitive profile. Although contribution of CLIP2 to the phenotype cannot be excluded when it is deleted in combination with other genes, our results support the hypothesis that GTF2IRD1 and GTF2I are the main genes causing the cognitive defects associated with Williams-Beuren syndrome.

Autistic disorder in patients with Williams-Beuren syndrome: a reconsideration of the Williams-Beuren syndrome phenotype

BACKGROUND

Williams-Beuren syndrome (WBS), a rare developmental disorder caused by deletion of contiguous genes at 7q11.23, has been characterized by strengths in socialization (overfriendliness) and communication (excessive talkativeness). WBS has been often considered as the polar opposite behavioral phenotype to autism. Our objective was to better understand the range of phenotypic expression in WBS and the relationship between WBS and autistic disorder.

METHODOLOGY

The study was conducted on 9 French individuals aged from 4 to 37 years old with autistic disorder associated with WBS. Behavioral assessments were performed using Autism Diagnostic Interview-Revised (ADI-R) and Autism Diagnostic Observation Schedule (ADOS) scales. Molecular characterization of the WBS critical region was performed by FISH.

FINDINGS

FISH analysis indicated that all 9 patients displayed the common WBS deletion. All 9 patients met ADI-R and ADOS diagnostic criteria for autism, displaying stereotypies and severe impairments in social interaction and communication (including the absence of expressive language). Additionally, patients showed improvement in social communication over time.

CONCLUSIONS

The results indicate that comorbid autism and WBS is more frequent than expected and suggest that the common WBS deletion can result in a continuum of social communication impairment, ranging from excessive talkativeness and overfriendliness to absence of verbal language and poor social relationships. Appreciation of the possible co-occurrence of WBS and autism challenges the common view that WBS represents the opposite behavioral phenotype of autism, and might lead to improved recognition of WBS in individuals diagnosed with autism.

Mutation of Gtf2ird1 from the Williams-Beuren syndrome critical region results in facial dysplasia, motor dysfunction, and altered vocalisations

Insufficiency of the transcriptional regulator GTF2IRD1 has become a strong potential explanation for some of the major characteristic features of the neurodevelopmental disorder Williams-Beuren syndrome (WBS). Genotype/phenotype correlations in humans indicate that the hemizygous loss of the GTF2IRD1 gene and an adjacent paralogue, GTF2I, play crucial roles in the neurocognitive and craniofacial aspects of the disease. In order to explore this genetic relationship in greater detail, we have generated a targeted Gtf2ird1 mutation in mice that blocks normal GTF2IRD1 protein production. Detailed analyses of homozygous null Gtf2ird1 mice have revealed a series of phenotypes that share some intriguing parallels with WBS. These include reduced body weight, a facial deformity resulting from localised epidermal hyperplasia, a motor coordination deficit, alterations in exploratory activity and, in response to specific stress-inducing stimuli; a novel audible vocalisation and increased serum corticosterone. Analysis of Gtf2ird1 expression patterns in the brain using a knock-in LacZ reporter and c-fos activity mapping illustrates the regions where these neurological abnormalities may originate. These data provide new mechanistic insight into the clinical genetic findings in WBS patients and indicate that insufficiency of GTF2IRD1 protein contributes to abnormalities of facial development, motor function and specific behavioural disorders that accompany this disease.

Biochemistry and biology of the inducible multifunctional transcription factor TFII-I: 10 years later

Exactly twenty years ago TFII-I was discovered as a biochemical entity that was able to bind to and function via a core promoter element called the Initiator (Inr). Since then several different properties of this signal-induced multifunctional factor were discovered. Here I update these ever expanding functions of TFII-I--focusing primarily on the last ten years since the first review appeared in this journal.

Global analysis of gene expression in the developing brain of Gtf2ird1 knockout mice

Background

Williams-Beuren Syndrome (WBS) is a neurodevelopmental disorder caused by a hemizygous deletion of a 1.5 Mb region on chromosome 7q11.23 encompassing 26 genes. One of these genes, GTF2IRD1, codes for a putative transcription factor that is expressed throughout the brain during development. Genotype-phenotype studies in patients with atypical deletions of 7q11.23 implicate this gene in the neurological features of WBS, and Gtf2ird1 knockout mice show reduced innate fear and increased sociability, consistent with features of WBS. Multiple studies have identified in vitro target genes of GTF2IRD1, but we sought to identify in vivo targets in the mouse brain.

Methodology/Principal Findings

We performed the first in vivo microarray screen for transcriptional targets of Gtf2ird1 in brain tissue from Gtf2ird1 knockout and wildtype mice at embryonic day 15.5 and at birth. Changes in gene expression in the mutant mice were moderate (0.5 to 2.5 fold) and of candidate genes with altered expression verified using real-time PCR, most were located on chromosome 5, within 10 Mb of Gtf2ird1. siRNA knock-down of Gtf2ird1 in two mouse neuronal cell lines failed to identify changes in expression of any of the genes identified from the microarray and subsequent analysis showed that differences in expression of genes on chromosome 5 were the result of retention of that chromosome region from the targeted embryonic stem cell line, and so were dependent upon strain rather than Gtf2ird1 genotype. In addition, specific analysis of genes previously identified as direct in vitro targets of GTF2IRD1 failed to show altered expression.

Conclusions/Significance

We have been unable to identify any in vivo neuronal targets of GTF2IRD1 through genome-wide expression analysis, despite widespread and robust expression of this protein in the developing rodent brain.

Using transcription modules to identify expression clusters perturbed in Williams-Beuren syndrome

The genetic dissection of the phenotypes associated with Williams-Beuren Syndrome (WBS) is advancing thanks to the study of individuals carrying typical or atypical structural rearrangements, as well as in vitro and animal studies. However, little is known about the global dysregulations caused by the WBS deletion. We profiled the transcriptomes of skin fibroblasts from WBS patients and compared them to matched controls. We identified 868 differentially expressed genes that were significantly enriched in extracellular matrix genes, major histocompatibility complex (MHC) genes, as well as genes in which the products localize to the postsynaptic membrane. We then used public expression datasets from human fibroblasts to establish transcription modules, sets of genes coexpressed in this cell type. We identified those sets in which the average gene expression was altered in WBS samples. Dysregulated modules are often interconnected and share multiple common genes, suggesting that intricate regulatory networks connected by a few central genes are disturbed in WBS. This modular approach increases the power to identify pathways dysregulated in WBS patients, thus providing a testable set of additional candidates for genes and their interactions that modulate the WBS phenotypes.

Intelligence in Williams Syndrome is related to STX1A, which encodes a component of the presynaptic SNARE complex

Although genetics is the most significant known determinant of human intelligence, specific gene contributions remain largely unknown. To accelerate understanding in this area, we have taken a new approach by studying the relationship between quantitative gene expression and intelligence in a cohort of 65 patients with Williams Syndrome (WS), a neurodevelopmental disorder caused by a 1.5 Mb deletion on chromosome 7q11.23. We find that variation in the transcript levels of the brain gene STX1A correlates significantly with intelligence in WS patients measured by principal component analysis (PCA) of standardized WAIS-R subtests, r  = 0.40 (Pearson correlation, Bonferroni corrected p-value  = 0.007), accounting for 15.6% of the cognitive variation. These results suggest that syntaxin 1A, a neuronal regulator of presynaptic vesicle release, may play a role in WS and be a component of the cellular pathway determining human intelligence.

Essential role of the N-terminal region of TFII-I in viability and behavior

Background

GTF2I codes for a general intrinsic transcription factor and calcium channel regulator TFII-I, with high and ubiquitous expression, and a strong candidate for involvement in the morphological and neuro-developmental anomalies of the Williams-Beuren syndrome (WBS). WBS is a genetic disorder due to a recurring deletion of about 1,55-1,83 Mb containing 25-28 genes in chromosome band 7q11.23 including GTF2I. Completed homozygous loss of either the Gtf2i or Gtf2ird1 function in mice provided additional evidence for the involvement of both genes in the craniofacial and cognitive phenotype. Unfortunately nothing is now about the behavioral characterization of heterozygous mice.

Methods

By gene targeting we have generated a mutant mice with a deletion of the first 140 amino-acids of TFII-I. mRNA and protein expression analysis were used to document the effect of the study deletion. We performed behavioral characterization of heterozygous mutant mice to document in vivo implications of TFII-I in the cognitive profile of WBS patients.

Results

Homozygous and heterozygous mutant mice exhibit craniofacial alterations, most clearly represented in homozygous condition. Behavioral test demonstrate that heterozygous mutant mice exhibit some neurobehavioral alterations and hyperacusis or odynacusis that could be associated with specific features of WBS phenotype. Homozygous mutant mice present highly compromised embryonic viability and fertility. Regarding cellular model, we documented a retarded growth in heterozygous MEFs respect to homozygous or wild-type MEFs.

Conclusion

Our data confirm that, although additive effects of haploinsufficiency at several genes may contribute to the full craniofacial or neurocognitive features of WBS, correct expression of GTF2I is one of the main players. In addition, these findings show that the deletion of the fist 140 amino-acids of TFII-I altered it correct function leading to a clear phenotype, at both levels, at the cellular model and at the in vivo model.

An atypical 7q11.23 deletion in a normal IQ Williams-Beuren syndrome patient

Williams-Beuren syndrome (WBS; OMIM no. 194050) is a multisystemic neurodevelopmental disorder caused by a hemizygous deletion of 1.55 Mb on chromosome 7q11.23 spanning 28 genes. Haploinsufficiency of the ELN gene was shown to be responsible for supravalvular aortic stenosis and generalized arteriopathy, whereas LIMK1, CLIP2, GTF2IRD1 and GTF2I genes were suggested to be linked to the specific cognitive profile and craniofacial features. These insights for genotype-phenotype correlations came from the molecular and clinical analysis of patients with atypical deletions and mice models. Here we report a patient showing mild WBS physical phenotype and normal IQ, who carries a shorter 1 Mb atypical deletion. This rearrangement does not include the GTF2IRD1 and GTF2I genes and only partially the BAZ1B gene. Our results are consistent with the hypothesis that hemizygosity of the GTF2IRD1 and GTF2I genes might be involved in the facial dysmorphisms and in the specific motor and cognitive deficits observed in WBS patients.

Negative autoregulation of GTF2IRD1 in Williams-Beuren syndrome via a novel DNA binding mechanism

The GTF2IRD1 gene is of principal interest to the study of Williams-Beuren syndrome (WBS). This neurodevelopmental disorder results from the hemizygous deletion of a region of chromosome 7q11.23 containing 28 genes including GTF2IRD1. WBS is thought to be caused by haploinsufficiency of certain dosage-sensitive genes within the deleted region, and the feature of supravalvular aortic stenosis (SVAS) has been attributed to reduced elastin caused by deletion of ELN. Human genetic mapping data have implicated two related genes GTF2IRD1 and GTF2I in the cause of some the key features of WBS, including craniofacial dysmorphology, hypersociability, and visuospatial deficits. Mice with mutations of the Gtf2ird1 allele show evidence of craniofacial abnormalities and behavioral changes. Here we show the existence of a negative autoregulatory mechanism that controls the level of GTF2IRD1 transcription via direct binding of the GTF2IRD1 protein to a highly conserved region of the GTF2IRD1 promoter containing an array of three binding sites. The affinity for this protein-DNA interaction is critically dependent upon multiple interactions between separate domains of the protein and at least two of the DNA binding sites. This autoregulatory mechanism leads to dosage compensation of GTF2IRD1 transcription in WBS patients. The GTF2IRD1 promoter represents the first established in vivo gene target of the GTF2IRD1 protein, and we use it to model its DNA interaction capabilities.

Insights into brain development from neurogenetic syndromes: evidence from fragile X syndrome, Williams syndrome, Turner syndrome and velocardiofacial syndrome

Over the past few decades, behavioral, neuroimaging and molecular studies of neurogenetic conditions, such as Williams, fragile X, Turner and velocardiofacial (22q11.2 deletion) syndromes, have led to important insights regarding brain development. These investigations allow researchers to examine "experiments of nature" in which the deletion or alteration of one gene or a contiguous set of genes can be linked to aberrant brain structure or function. Converging evidence across multiple imaging modalities has now begun to highlight the abnormal neural circuitry characterizing many individual neurogenetic syndromes. Furthermore, there has been renewed interest in combining analyses across neurogenetic conditions in order to search for common organizing principles in development. In this review, we highlight converging evidence across syndromes from multiple neuroimaging modalities, with a particular emphasis on functional imaging. In addition, we discuss the commonalities and differences pertaining to selective deficits in visuospatial processing that occur across four neurogenetic syndromes. We suggest avenues for future exploration, with the goal of achieving a deeper understanding of the neural abnormalities in these affected populations.

Williams-Beuren syndrome-associated transcription factor TFII-I regulates osteogenic marker genes

Williams-Beuren syndrome (WBS), an autosomal dominant genetic disorder, is characterized by a unique cognitive profile and craniofacial defects. WBS results from a microdeletion at the chromosomal location 7q11.23 that encompasses the genes encoding the members of TFII-I family of transcription factors. Given that the haploinsufficiency for TFII-I is causative to the craniofacial phenotype in humans, we set out to analyze the effect of post-transcriptional silencing of TFII-I during BMP-2-driven osteoblast differentiation in the C2C12 cell line. Our results show that TFII-I plays an inhibitory role in regulating genes that are essential in osteogenesis and intersects with the bone-specific transcription factor Runx2 and the retinoblastoma protein, pRb. Identification of pathways regulated by TFII-I family transcription factors may begin to shed light on the molecular determinants of WBS.

A genome-wide linkage and association scan reveals novel loci for autism

Although autism is a highly heritable neurodevelopmental disorder, attempts to identify specific susceptibility genes have thus far met with limited success. Genome-wide association studies using half a million or more markers, particularly those with very large sample sizes achieved through meta-analysis, have shown great success in mapping genes for other complex genetic traits. Consequently, we initiated a linkage and association mapping study using half a million genome-wide single nucleotide polymorphisms (SNPs) in a common set of 1,031 multiplex autism families (1,553 affected offspring). We identified regions of suggestive and significant linkage on chromosomes 6q27 and 20p13, respectively. Initial analysis did not yield genome-wide significant associations; however, genotyping of top hits in additional families revealed an SNP on chromosome 5p15 (between SEMA5A and TAS2R1) that was significantly associated with autism (P = 2 x 10(-7)). We also demonstrated that expression of SEMA5A is reduced in brains from autistic patients, further implicating SEMA5A as an autism susceptibility gene. The linkage regions reported here provide targets for rare variation screening whereas the discovery of a single novel association demonstrates the action of common variants.

Autism, language delay and mental retardation in a patient with 7q11 duplication

Chromosomal rearrangements are found in a subset of patients with autism. Duplications involving loci associated with behavioural disturbances constitute an especially good candidate mechanism. The Williams-Beuren critical region (WBCR), located at 7q11.23, is commonly deleted in Williams-Beuren microdeletion syndrome (WBS). However, only four patients with a duplication of the WBCR have been reported to date. Here, 206 patients with autism spectrum disorders were screened for the WBCR duplication by quantitative microsatellite analysis and multiple ligation-dependent probe amplification. One male patient with a de novo interstitial duplication of the entire WBCR of paternal origin was identified. The patient had autistic disorder, severe language delay and mental retardation, with mild dysmorphism. The present report concerns the first patient with autistic disorder and a WBCR duplication. This observation indicates that the 7q11.23 duplication could be involved in complex clinical phenotypes, ranging from developmental or language delay to mental retardation and autism.