GTF2I hemizygosity implicated in mental retardation in Williams syndrome: Genotype-phenotype analysis of five families with deletions in the Williams syndrome region

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.

A role for transcription factor GTF2IRD2 in executive function in Williams-Beuren syndrome

Executive functions are amongst the most heritable cognitive traits with twin studies indicating a strong genetic origin. However genes associated with this domain are unknown. Our research into the neurodevelopmental disorder Williams-Beuren syndrome (WBS) has identified a gene within the causative recurrent 1.5/1.6 Mb heterozygous microdeletion on chromosome 7q11.23, which may be involved in executive functioning. Comparative genome array screening of 55 WBS patients revealed a larger ∼1.8 Mb microdeletion in 18% of cases, which results in the loss of an additional gene, the transcription factor GTF2IRD2. The GTF gene family of transcription factors (GTF2I, GTF2IRD1 and GTF2IRD2) are all highly expressed in the brain, and GTF2I and GTF2IRD1 are involved in the pathogenesis of the cognitive and behavioural phenotypes associated with WBS. A multi-level analysis of cognitive, behavioural and psychological functioning in WBS patients showed that those with slightly larger deletions encompassing GTF2IRD2 were significantly more cognitively impaired in the areas of spatial functioning, social reasoning, and cognitive flexibility (a form of executive functioning). They also displayed significantly more obsessions and externalizing behaviours, a likely manifestation of poor cognitive flexibility and executive dysfunction. We provide the first evidence for a role for GTF2IRD2 in higher-level (executive functioning) abilities and highlight the importance of integrating detailed molecular characterisation of patients with comprehensive neuropsychological profiling to uncover additional genotype-phenotype correlations. The identification of specific genes which contribute to executive function has important neuropsychological implications in the treatment of patients with conditions like WBS, and will allow further studies into their mechanism of action.

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.

Social cognition in williams syndrome: genotype/phenotype insights from partial deletion patients

Identifying genotype/phenotype relations in human social cognition has been enhanced by the study of Williams syndrome (WS). Indeed, individuals with WS present with a particularly strong social drive, and researchers have sought to link deleted genes in the WS critical region (WSCR) of chromosome 7q11.23 to this unusual social profile. In this paper, we provide details of two case studies of children with partial genetic deletions in the WSCR: an 11-year-old female with a deletion of 24 of the 28 WS genes, and a 14-year-old male who presents with the opposite profile, i.e., the deletion of only four genes at the telomeric end of the WSCR. We tested these two children on a large battery of standardized and experimental social perception and social cognition tasks - both implicit and explicit - as well as standardized social questionnaires and general psychometric measures. Our findings reveal a partial WS socio-cognitive profile in the female, contrasted with a more autistic-like profile in the male. We discuss the implications of these findings for genotype/phenotype relations, as well as the advantages and limitations of animal models and of case study approaches.

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.

Psychiatric features in children with genetic syndromes: toward functional phenotypes

Neurodevelopmental disorders with identified genetic etiologies present a unique opportunity to study gene-brain-behavior connections in child psychiatry. Parsing complex human behavior into dissociable components is facilitated by examining a relatively homogenous genetic population. As children with developmental delay carry a greater burden of mental illness than the general population, familiarity with the most common genetic disorders will serve practitioners seeing a general child population. In this article, basic genetic testing and 11 of the most common genetic disorders are reviewed, including the evidence base for treatment. Based on their training in child development, family systems, and multimodal treatment, child psychiatrists are well positioned to integrate cognitive, behavioral, social, psychiatric, and physical phenotypes, with a focus on functional impairment.

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.

Animal models of Williams syndrome

In recent years, researchers have generated a variety of mouse models in an attempt to dissect the contribution of individual genes to the complex phenotype associated with Williams syndrome (WS). The mouse genome is easily manipulated to produce animals that are copies of humans with genetic conditions, be it with null mutations, hypomorphic mutations, point mutations, or even large deletions encompassing many genes. The existing mouse models certainly seem to implicate hemizygosity for ELN, BAZ1B, CLIP2, and GTF2IRD1 in WS, and new mice with large deletions of the WS region are helping us to understand both the additive and potential combinatorial effects of hemizygosity for specific genes. However, not all genes that are haploinsufficient in humans prove to be so in mice and the effect of genetic background can also have a significant effect on the penetrance of many phenotypes. Thus although mouse models are powerful tools, the information garnered from their study must be carefully interpreted. Nevertheless, mouse models look set to provide a wealth of information about the neuroanatomy, neurophysiology and molecular pathways that underlie WS and in the future will act as essential tools for the development and testing of therapeutics.

High prevalence of diabetes and pre-diabetes in adults with Williams syndrome

A standard oral glucose tolerance test (OGTT) was administered to 28 adults with Williams syndrome (WS). Three quarters of the WS subjects showed abnormal glucose curves, meeting diagnostic criteria for either diabetes or the pre-diabetic state of impaired glucose tolerance. Fasting mean glucose and median insulin levels did not differ significantly in the total WS cohort versus age-gender-BMI matched controls, though the glucose area under the curve was greater in the WS subjects. HbA1c levels were not as reliable as the OGTT in diagnosing the presence of diabetes. Given the high prevalence of impaired glucose regulation, adults with WS should be screened for diabetes, and when present should be treated in accordance with standard medical practice. Hemizygosity for a gene mapping to the Williams syndrome chromosome region (WSCR) is likely the major factor responsible for the high frequency of diabetes in WS. Syntaxin-1A is a prime candidate gene based on its location in the WSCR, its role in insulin release, and the presence of abnormal glucose metabolism in mouse models with aberrantly expressed Stx-1a.

Introduction: Williams syndrome

In the nearly 50 years since the description of Williams syndrome by [Williams et al. (1961); Circulation 24:1311-1318], the focus of scientific inquiry has shifted from identification, definition, and description of the syndrome in small series to genotype-phenotype correlation, pathophysiologic investigation in both humans and in animal models, and therapeutic outcomes in large cohorts. Study of this rare syndrome has provided insight into the structure and function of the extracellular matrix, has contributed to understanding of genomic structure and rearrangement, and is beginning to elucidate genetic underpinnings of learning, language, and behavior. The results of current research not only recommend interventions that can be implemented now, but also identify areas requiring additional investigation, and suggest future therapeutic approaches.

Inversion of the Williams syndrome region is a common polymorphism found more frequently in parents of children with Williams syndrome

Williams syndrome (WS) is a multisystem disorder caused by deletion of about 1.55 Mb of DNA (including 26 genes) on chromosome 7q11.23, a region predisposed to recombination due to its genomic structure. Deletion of the Williams syndrome chromosome region (WSCR) occurs sporadically. To better define chance for familial recurrence and to investigate the prevalence of genomic rearrangements of the region, 257 children with WS and their parents were studied. We determined deletion size in probands by metaphase FISH, parent-of-origin of the deleted chromosome by molecular genetic methods, and inversion status of the WSCR in both parents by interphase FISH. The frequency of WSCR inversion in the transmitting parent group was 24.9%. In contrast, the rate of inversion in the non-transmitting parent group (a reasonable estimate of the rate in the general population) was 5.8%. There were no significant gender differences with respect to parent-of-origin for the deleted chromosome or the incidence of the inversion polymorphism. There was no difference in the rate of spontaneous abortion for mothers heterozygous for the WSCR inversion relative to mothers without the inversion. We calculate that for a parent heterozygous for a WSCR inversion, the chance to have a child with WS is about 1 in 1,750, in contrast to the 1 in 9,500 chance for a parent without an inversion.

Genome rearrangements detected by SNP microarrays in individuals with intellectual disability referred with possible Williams syndrome

Background

Intellectual disability (ID) affects 2–3% of the population and may occur with or without multiple congenital anomalies (MCA) or other medical conditions. Established genetic syndromes and visible chromosome abnormalities account for a substantial percentage of ID diagnoses, although for ∼50% the molecular etiology is unknown. Individuals with features suggestive of various syndromes but lacking their associated genetic anomalies pose a formidable clinical challenge. With the advent of microarray techniques, submicroscopic genome alterations not associated with known syndromes are emerging as a significant cause of ID and MCA.

Methodology/Principal Findings

High-density SNP microarrays were used to determine genome wide copy number in 42 individuals: 7 with confirmed alterations in the WS region but atypical clinical phenotypes, 31 with ID and/or MCA, and 4 controls. One individual from the first group had the most telomeric gene in the WS critical region deleted along with 2 Mb of flanking sequence. A second person had the classic WS deletion and a rearrangement on chromosome 5p within the Cri du Chat syndrome (OMIM:123450) region. Six individuals from the ID/MCA group had large rearrangements (3 deletions, 3 duplications), one of whom had a large inversion associated with a deletion that was not detected by the SNP arrays.

Conclusions/Significance

Combining SNP microarray analyses and qPCR allowed us to clone and sequence 21 deletion breakpoints in individuals with atypical deletions in the WS region and/or ID or MCA. Comparison of these breakpoints to databases of genomic variation revealed that 52% occurred in regions harboring structural variants in the general population. For two probands the genomic alterations were flanked by segmental duplications, which frequently mediate recurrent genome rearrangements; these may represent new genomic disorders. While SNP arrays and related technologies can identify potentially pathogenic deletions and duplications, obtaining sequence information from the breakpoints frequently provides additional information.

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.

Psychiatric features in children with genetic syndromes: toward functional phenotypes

Neurodevelopmental disorders with identified genetic etiologies present a unique opportunity to study gene-brain-behavior connections in child psychiatry. Parsing complex human behavior into dissociable components is facilitated by examining a relatively homogenous genetic population. As children with developmental delay carry a greater burden of mental illness than the general population, familiarity with the most common genetic disorders will serve practitioners seeing a general child population. In this article basic genetic testing and 11 of the most common genetic disorders are reviewed, including the evidence base for treatment. Based on their training in child development, family systems, and multimodal treatment, child psychiatrists are well positioned to integrate cognitive, behavioral, social, psychiatric, and physical phenotypes, with a focus on functional impairment.

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

Investigating the relationship between genes and the neural substrates of complex human behavior promises to provide essential insight into the pathophysiology of mental disorders. One approach to this inquiry is through neuroimaging of individuals with microdeletion syndromes that manifest in specific neuropsychiatric phenotypes. Both Velocardiofacial syndrome (VCFS) and Williams syndrome (WS) involve haploinsufficiency of a relatively small set of identified genes on the one hand and association with distinct, clinically relevant behavioral and cognitive profiles on the other hand. In VCFS, there is a deletion in chromosomal region 22q11.2 and a resultant predilection toward psychosis, poor arithmetic proficiency, and low performance intelligence quotients. In WS, there is a deletion in chromosomal region 7q11.23 and a resultant predilection toward hypersociability, non-social anxiety, impaired visuospatial construction, and often intellectual impairment. Structural and functional neuroimaging studies have begun not only to map these well-defined genetic alterations to systems-level brain abnormalities, but also to identify relationships between neural phenotypes and particular genes within the critical deletion regions. Though neuroimaging of both VCFS and WS presents specific, formidable methodological challenges, including comparison subject selection and accounting for neuroanatomical and vascular anomalies in patients, and many questions remain, the literature to date on these syndromes, reviewed herein, constitutes a fruitful "bottom-up" approach to defining gene-brain relationships.

Auditory attraction: activation of visual cortex by music and sound in Williams syndrome

Williams syndrome is a genetic neurodevelopmental disorder with a distinctive phenotype, including cognitive-linguistic features, nonsocial anxiety, and a strong attraction to music. we preformed functional MRI studies examining brain responses to musical and other types of stimuli in young adults with Williams syndrome and typically developing controls. In Study 1, the Williams syndrome group exhibited unforeseen activations of the visual cortex to musical stimuli, and it was this novel finding that became the focus of two subsequent studies. Using retinotopy, color localizers, and additional sound conditions, we identified specific visual areas in subjects with Williams syndrome that were activated by both musical and nonmusical auditory stimuli. The results, similar to synthetic-like experiences, have implications for cross-modal sensory processing in typical and atypical neurodevelopment.

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.

More than the sum of its parts: new mouse models for dissecting the genetic complexities of Williams-Beuren syndrome

Psychiatric disorders are a common, severe and disabling group of diseases where progress in finding novel molecular targets has been slow. This is partly due to our lack of understanding of the molecular pathophysiology of these conditions as they play out in the brain (Insel & Scolnick, 2006). Since many of these diseases (such as schizophrenia, bipolar disorder or autism) are highly heritable, a genetic approach to dissecting the risk architecture is a promising avenue for molecular medicine; however, variants in single genes frequently present in the population have only small to moderate effects on complex behavioural phenotypes (O'Donovan et al, 2008).

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.

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.

Is it Williams syndrome? GTF2IRD1 implicated in visual-spatial construction and GTF2I in sociability revealed by high resolution arrays

Genetic contributions to human cognition and behavior are clear but difficult to define. Williams syndrome (WS) provides a unique model for relating single genes to visual-spatial cognition and social behavior. We defined a approximately 1.5 Mb region of approximately 25 genes deleted in >98% of typical WS and then rare small deletions, showing that visual-spatial construction (VSC) in WS was associated with the genes GTF2IRD1 and GTF2I. To distinguish the roles of GTF2IRD1 and GTF2I in VSC and social behavior, we utilized multiple genomic methods (custom high resolution oligonucleotide microarray, multicolor FISH and somatic cell hybrids analyzed by PCR) to identify individuals deleted for either gene but not both. We analyzed genetic, cognitive and social behavior in a unique individual with WS features (heart defects, small size, facies), but with an atypical deletion of a set of genes that includes GTF2IRD1, but not GTF2I. The centromeric breakpoint localized to the region 72.32-72.38 Mb and the telomeric breakpoint to 72.66 Mb, 10 kb downstream of GTF2IRD1. Cognitive testing (WPPSI-R, K-BIT, and PLS-3) demonstrated striking deficits in VSC (Block Design, Object Assembly) but overall performance 1.5-3 SD above WS means. We have now integrated the genetic, clinical and cognitive data with previous reports of social behavior in this subject. These results combine with previous data from small deletions to suggest the gene GTF2IRD1 is associated with WS facies and VSC, and that GTF2I may contribute to WS social behaviors including increased gaze and attention to strangers.

Mechanisms and treatment of cardiovascular disease in Williams-Beuren syndrome

Williams-Beuren syndrome (WBS) is a microdeletion disorder caused by heterozygous loss of approximately 1.5-Mb pairs of DNA from chromosome 7. Patients with WBS have a characteristic constellation of medical and cognitive findings, with a hallmark feature of generalized arteriopathy presenting as stenoses of elastic arteries and hypertension. Human and mouse studies establish that defects in the elastin gene, leading to elastin haploinsufficiency, underlie the arteriopathy. In this review we describe potential links between elastin expression and arteriopathy, possible explanations for disease variability, and current treatment options and their limitations, and we propose several new directions for the development of nonsurgical preventative therapies based on insights from elastin biology.

Defining the social phenotype in Williams syndrome: a model for linking gene, the brain, and behavior

Research into phenotype-genotype correlations in neurodevelopmental disorders has greatly elucidated the contribution of genetic and neurobiological factors to variations in typical and atypical development. Etiologically relatively homogeneous disorders, such as Williams syndrome (WS), provide unique opportunities for elucidating gene-brain-behavior relationships. WS is a neurogenetic disorder caused by a hemizygous deletion of approximately 25 genes on chromosome 7q11.23. This results in a cascade of physical, cognitive-behavioral, affective, and neurobiological aberrations. WS is associated with a markedly uneven neurocognitive profile, and the mature state cognitive profile of WS is relatively well developed. Although anecdotally, individuals with WS have been frequently described as unusually friendly and sociable, personality remains a considerably less well studied area. This paper investigates genetic influences, cognitive-behavioral characteristics, aberrations in brain structure and function, and environmental and biological variables that influence the social outcomes of individuals with WS. We bring together a series of findings across multiple levels of scientific enquiry to examine the social phenotype in WS, reflecting the journey from gene to the brain to behavior. Understanding the complex multilevel scientific perspective in WS has implications for understanding typical social development by identifying important developmental events and markers, as well as helping to define the boundaries of psychopathology.

Determination and functional analysis of the consensus binding site for TFII-I family member BEN, implicated in Williams-Beuren syndrome

The ubiquitously expressed TFII-I family of multifunctional transcription factors is involved in gene regulation as well as signaling. Despite the fact that they share significant sequence homology, these factors exhibit varied and distinct functions. The lack of knowledge about its binding sites and physiological target genes makes it more difficult to assign a definitive function for the TFII-I-related protein, BEN. We set out to determine its optimal binding site with the notion of predicting its physiological target genes. Here we report the identification of an optimal binding sequence for BEN by SELEX (systematic evolution of ligands by exponential enrichment) and confirm the relevance of this sequence by functional assays. We further performed a data base search to assign genes that have this consensus site(s) and validate several candidate genes by quantitative PCR upon stable silencing of BEN and by chromatin immunoprecipitation assay upon stable expression of BEN. Given that haploinsufficiency in BEN is causative to Williams-Beuren syndrome, these results may further lead to the identification of a set of physiologically relevant target genes for BEN and may help identify molecular determinants of Williams-Beuren syndrome.

Williams-Beuren syndrome TRIM50 encodes an E3 ubiquitin ligase

Williams-Beuren syndrome (WBS) is a neurodevelopmental and multisystemic disease that results from hemizygosity of approximately 25 genes mapping to chromosomal region 7q11.23. We report here the preliminary description of eight novel genes mapping within the WBS critical region and/or its syntenic mouse region. Three of these genes, TRIM50, TRIM73 and TRIM74, belong to the TRIpartite motif gene family, members of which were shown to be associated to several human genetic diseases. We describe the preliminary functional characterization of these genes and show that Trim50 encodes an E3 ubiquitin ligase, opening the interesting hypothesis that the ubiquitin-mediated proteasome pathway might be involved in the WBS phenotype.

Neural phenotypes of common and rare genetic variants

Neuroimaging methods offer a powerful way to bridge the gaps between genes, neurobiology and behavior. Such investigations may be further empowered by complementary strategies involving chromosomal abnormalities associated with particular neurobehavioral phenotypes, which can help to localize causative genes and better understand the genetics of complex traits in the general population. Here we review the evidence from studies using these convergent approaches to investigate genetic influences on brain structure: (1) studies of common genetic variations associated with particular neuroanatomic phenotypes, and (2) studies of possible 'genetic subtypes' of neuropsychiatric disorders with very high penetrance, with a focus on neuroimaging studies using novel computational brain mapping algorithms. Finally, we discuss the contribution of behavioral neurogenetics research to our understanding of the genetic basis of neuropsychiatric disorders in the broader population.

Visual phenotype in Williams-Beuren syndrome challenges magnocellular theories explaining human neurodevelopmental visual cortical disorders

Williams-Beuren syndrome (WBS), a neurodevelopmental genetic disorder whose manifestations include visuospatial impairment, provides a unique model to link genetically determined loss of neural cell populations at different levels of the nervous system with neural circuits and visual behavior. Given that several of the genes deleted in WBS are also involved in eye development and the differentiation of retinal layers, we examined the retinal phenotype in WBS patients and its functional relation to global motion perception. We discovered a low-level visual phenotype characterized by decreased retinal thickness, abnormal optic disk concavity, and impaired visual responses in WBS patients compared with age-matched controls by using electrophysiology, confocal and coherence in vivo imaging with cellular resolution, and psychophysics. These mechanisms of impairment are related to the magnocellular pathway, which is involved in the detection of temporal changes in the visual scene. Low-level magnocellular performance did not predict high-level deficits in the integration of motion and 3D information at higher levels, thereby demonstrating independent mechanisms of dysfunction in WBS that will require remediation strategies different from those used in other visuospatial disorders. These findings challenge neurodevelopmental theories that explain cortical deficits based on low-level magnocellular impairment, such as regarding dyslexia.

Socio-communicative deficits in young children with Williams syndrome: performance on the Autism Diagnostic Observation Schedule

In this investigation, the socio-communicative skills of 29 children with Williams syndrome aged 2 (1/2) to 5 (1/2) years were examined using the Autism Diagnostic Observation Schedule (ADOS) Module 1. Most of the participants showed socio-communicative difficulties. Approximately half of the participants were classified by the ADOS algorithm as "autism spectrum." Three participants were classified "autism." Difficulties with pointing, gestures, giving, showing, and eye contact were present for more than half of the participants, with many also showing difficulties with initiation and response to joint attention and with integration of gaze with other behaviors. Expressive and receptive language abilities of the children with Williams syndrome classified "autism spectrum" were weaker than for children classified nonspectrum, but expressive and receptive language level did not account for the socio-communicative difficulties. Implications for our understanding of the socio-communicative abilities of young children with Williams syndrome and diagnostic practices regarding dual diagnosis are discussed.

Reduced fear and aggression and altered serotonin metabolism in Gtf2ird1-targeted mice

The GTF2IRD1 general transcription factor is a candidate for involvement in the varied cognitive and neurobehavioral symptoms of the microdeletion disorder, Williams-Beuren syndrome (WBS). We show that mice with heterozygous or homozygous disruption of Gtf2ird1 exhibit decreased fear and aggression and increased social behaviors. These findings are reminiscent of the hypersociability and diminished fear of strangers that are hallmarks of WBS. Other core features of WBS, such as increased anxiety and problems with spatial learning were not present in the targeted mice. Investigation of a possible neurochemical basis for the altered behaviors in these mice using high-performance liquid chromatography analysis showed increased levels of serotonin metabolites in several brain regions, including the amygdala, frontal cortex and parietal cortex. Serotonin levels have previously been implicated in fear and aggression, through modulation of the neural pathway connecting the prefrontal cortex and amygdala. These results suggest that hemizygosity for GTF2IRD1 may play a role in the complex behavioral phenotype seen in patients with WBS, either individually, or in combination with other genes, and that the GTF2I transcription factors may influence fear and social behavior through the alteration of neurochemical pathways.

Imaging genetics for neuropsychiatric disorders

Many neuropsychiatric disorders of childhood and adolescence have a strong genetic component, and all present challenging questions about the neural abnormalities that underlie complex and unique behavioral and cognitive phenotypes. A useful research strategy in this setting is imaging genetics, a relatively new approach that combines genetic assessment with multimodal neuroimaging to discover neural systems linked to genetic abnormalities or variation. In this article, the authors review this strategy as applied to two areas. First, the authors present results on dissecting neural mechanisms underlying the complex neuropsychiatric phenotype of Williams syndrome. Second, they examine neural systems that are linked to candidate gene genetic variation that mediate risk for psychiatric disorders in a gene by environmental interaction. These data provide convergent evidence for neural circuitry mediating emotional regulation and social cognition under genetic control in humans.

Rearrangements of the Williams-Beuren syndrome locus: molecular basis and implications for speech and language development

The Williams-Beuren syndrome (WBS) locus on human chromosome 7q11.23 is flanked by complex chromosome-specific low-copy repeats that mediate recurrent genomic rearrangements of the region. Common genomic rearrangements arise through unequal meiotic recombination and result in complex but distinct behavioural and cognitive phenotypes. Deletion of 7q11.23 results in WBS, which is characterised by mild to moderate intellectual disability or learning difficulties, with relative cognitive strengths in verbal short-term memory and in language and extreme weakness in visuospatial construction, as well as anxiety, attention-deficit hyperactivity disorder and overfriendliness. By contrast, duplication results in severely delayed speech and expressive language, with relative strength in visuospatial construction. Although deletion and duplication of the WBS region have very different effects, both cause forms of language impairment and suggest that dosage-sensitive genes within the region are important for the proper development of human speech and language. The spectrum and frequency of genomic rearrangements at 7q11.23 presents an exceptional opportunity to identify gene(s) directly involved in human speech and language development.

Presenting phenotype and clinical evaluation in a cohort of 22 Williams-Beuren syndrome patients

Williams-Beuren syndrome (WS) is a rare multi-system genomic disorder, caused by 7q11.23 microdeletion with a prevalence of 1/7500-1/20,000 live births. Clinical phenotype includes typical facial dysmorphism (elfin face), mental retardation associated with a peculiar neuropsychological profile and congenital heart defects. We investigated 22 WS patients (mean age of 9.7 years, range 1 day to 39 years) with a multi-specialist follow-up protocol comprehensive of neuropsychological, cardiologic, nephrologic, ophthalmologic, endocrinologic, gastroenterologic, odontostomatologic and orthopaedic evaluations. The mean age at diagnosis was 5.38 years, being 1.02 years when genetic evaluation was requested for congenital heart defects (CHD) and 10.68 years in case of mental retardation and/or abnormal neuropsychological profile without an evident CHD. All patients showed facial dysmorphisms, with supravalvular aortic stenosis (SVAS) as the most common cardiovascular anomaly (12/22), followed by peripheral pulmonary stenosis (9/22); interestingly, in one patient we detected a total anomalous pulmonary venous return (TAPVR), confirming the possible association of this rare CHD with WS. Hypertension was detected by 24-h ambulatory blood pressure monitoring in 7/22 cases. A cognitive assessment was performed in 13 patients older than 6 years, showing various degrees of mental retardation in 12 and a normal intelligence quotient (IQ) in a single patient; evaluation of developmental milestones revealed various grades of developmental delay in all the patients younger than 6 years. Chiari malformation type 1 was found in 3 patients. Our study underlines a remarkable diagnostic delay in patients who present to genetic evaluation because of mental retardation and/or peculiar neuropsychological profile lacking an evident cardiopathy and confirms the multi-systemic nature of WS leading to a high clinical presentation's variability and complex follow-up strategies.

Neurodevelopmental and behavioral issues in Williams syndrome

Much existing research on Williams syndrome (WS) has focused on the individuals' unusual cognitive profile, with less emphasis placed on the developmental and neural underpinnings of the disorder. We review recent findings from brain imaging and begin to discuss links from these data to the behavioral phenotype. Overall brain size is significantly reduced in individuals with WS, as it is in many mental retardation syndromes. However, the specific profile of deficits in WS, particularly the visuospatial deficits, appears to be linked to parietal lobe abnormalities. Results from both genetic and brain imaging studies have provided useful insights into WS neurobiology. However, future work needs to remediate the lack of studies investigating developmental processes.

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

BACKGROUND

Chromosomal rearrangements, arising from unequal recombination between repeated sequences, 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: one with severe language delay and the three others with variable developmental, psychomotor and language delay.

OBJECTIVE AND METHODS

In this study, we screened 206 patients with autism spectrum disorders for the WBCR duplication by quantitative microsatellite analysis and multiple ligation-dependent probe amplification.

RESULTS

We identified one male patient with a de novo interstitial duplication of the entire WBCR of paternal origin. The patient had autistic disorder, severe language delay and mental retardation, with very mild dysmorphic features.

CONCLUSION

We report 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, and extends the phenotype initially reported. These findings also support the existence of one or several genes in 7q11.23 sensitive to gene dosage and involved in the development of language and social interaction.

Gene expression analysis of TFII-I modulated genes in mouse embryonic fibroblasts

TFII-I is a founding member of a family of helix-loop-helix transcription factors involved in modulation of genes through interaction with various nuclear factors and chromatin remodeling complexes. Recent studies indicate that TFII-I performs important function in cell physiology and mouse embryogenesis. In order to understand its molecular role, TFII-I was overexpressed in primary mouse embryonic fibroblasts (MEFs) and alterations in gene expression were monitored with a mouse 16 K oligonucleotide microarray. These studies allowed us to identify genes that lie downstream of TFII-I-dependent pathways. Among the modulated candidates were genes involved in the immunity response, catalytic activity, signaling pathways and transcriptional regulation. Expression of several candidates including those for the interferon-stimulated protein (G1p2), small inducible cytokine A7 (Ccl7), ubiquitin-conjugating enzyme 8 (Ube2l6), cysteine-rich protein (Csrp2) and Drosophila delta-like 1 homolog (Dlk1) were confirmed by real-time PCR. The obtained results suggest that TFII-I participates in multiple signaling and regulatory pathways in MEFs.

Genes, language development, and language disorders

Genetic factors are important contributors to language and learning disorders, and discovery of the underlying genes can help delineate the basic neurological pathways that are involved. This information, in turn, can help define disorders and their perceptual and processing deficits. Initial molecular genetic studies of dyslexia, for example, appear to converge on defects in neuronal and axonal migration. Further study of individuals with abnormalities of these genes may lead to the recognition of characteristic cognitive deficits attributable to the neurological dysfunction. Such abnormalities may affect other disorders as well, and studies of co-morbidity of dyslexia with attention deficit disorder and speech sound disorder are helping to define the scope of these genes and show the etiological and cognitive commonalities between these conditions. The genetic contributions to specific language impairment (SLI) are not as well defined at this time, but similar molecular approaches are being applied to identify genes that influence SLI and comorbid disorders. While there is co-morbidity of SLI with dyslexia, it appears that most of the common genetic effects may be with the language characteristics of autism spectrum disorders rather than with dyslexia and related disorders. Identification of these genes and their neurological and cognitive effects should lay out a functional network of interacting genes and pathways that subserve language development. Understanding these processes can form the basis for refined procedures for diagnosis and treatment.

Contribution of CYLN2 and GTF2IRD1 to neurological and cognitive symptoms in Williams Syndrome

Williams Syndrome (WS, [MIM 194050]) is a disorder caused by a hemizygous deletion of 25-30 genes on chromosome 7q11.23. Several of these genes including those encoding cytoplasmic linker protein-115 (CYLN2) and general transcription factors (GTF2I and GTF2IRD1) are expressed in the brain and may contribute to the distinct neurological and cognitive deficits in WS patients. Recent studies of patients with partial deletions indicate that hemizygosity of GTF2I probably contributes to mental retardation in WS. Here we investigate whether CYLN2 and GTF2IRD1 contribute to the motoric and cognitive deficits in WS. Behavioral assessment of a new patient in which STX1A and LIMK1, but not CYLN2 and GTF2IRD1, are deleted showed that his cognitive and motor coordination functions were significantly better than in typical WS patients. Comparative analyses of gene specific CYLN2 and GTF2IRD1 knockout mice showed that a reduced size of the corpus callosum as well as deficits in motor coordination and hippocampal memory formation may be attributed to a deletion of CYLN2, while increased ventricle volume can be attributed to both CYLN2 and GTF2IRD1. We conclude that the motor and cognitive deficits in Williams Syndrome are caused by a variety of genes and that heterozygous deletion of CYLN2 is one of the major causes responsible for such dysfunctions.

Genomic rearrangements and gene copy-number alterations as a cause of nervous system disorders

Genomic disorders are a group of human genetic diseases caused by genomic rearrangements resulting in copy-number variation (CNV) affecting a dosage-sensitive gene or genes critical for normal development or maintenance. These disorders represent a wide range of clinically distinct entities but include many diseases affecting nervous system function. Herein, we review selected neurodevelopmental, neurodegenerative, and psychiatric disorders either known or suggested to be caused by genomic rearrangement and CNV. Further, we emphasize the cause-and-effect relationship between gene CNV and complex disease traits. We also discuss the prevalence and heritability of CNV, the correlation between CNV and higher-order genome architecture, and the heritability of personality, behavioral, and psychiatric traits. We speculate that CNV could underlie a significant proportion of normal human variation including differences in cognitive, behavioral, and psychological features.

Submicroscopic deletion in patients with Williams-Beuren syndrome influences expression levels of the nonhemizygous flanking genes

Genomic imbalance is a common cause of phenotypic abnormalities. We measured the relative expression level of genes that map within the microdeletion that causes Williams-Beuren syndrome and within its flanking regions. We found, unexpectedly, that not only hemizygous genes but also normal-copy neighboring genes show decreased relative levels of expression. Our results suggest that not only the aneuploid genes but also the flanking genes that map several megabases away from a genomic rearrangement should be considered possible contributors to the phenotypic variation in genomic disorders.

The jewels of our genome: the search for the genomic changes underlying the evolutionarily unique capacities of the human brain

The recent publication of the initial sequence and analysis of the chimp genome allows us, for the first time, to compare our genome with that of our closest living evolutionary relative. With more primate genome sequences being pursued, and with other genome-wide, cross-species comparative techniques emerging, we are entering an era in which we will be able to carry out genomic comparisons of unprecedented scope and detail. These studies should yield a bounty of new insights about the genes and genomic features that are unique to our species as well as those that are unique to other primate lineages, and may begin to causally link some of these to lineage-specific phenotypic characteristics. The most intriguing potential of these new approaches will be in the area of evolutionary neurogenomics and in the possibility that the key human lineage–specific (HLS) genomic changes that underlie the evolution of the human brain will be identified. Such new knowledge should provide fresh insights into neuronal development and higher cognitive function and dysfunction, and may possibly uncover biological mechanisms for information storage, analysis, and retrieval never previously seen.