An atypical deletion of the Williams-Beuren syndrome interval implicates genes associated with defective visuospatial processing and autism

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.

Melatonin in Neurodevelopmental Disorders: A Critical Literature Review

The article presents a review of the relationships between melatonin and neurodevelopmental disorders. First, the antioxidant properties of melatonin and its physiological effects are considered to understand better the role of melatonin in typical and atypical neurodevelopment. Then, several neurodevelopmental disorders occurring during infancy, such as autism spectrum disorder or neurogenetic disorders associated with autism (including Smith-Magenis syndrome, Angelman syndrome, Rett's syndrome, Tuberous sclerosis, or Williams-Beuren syndrome) and neurodevelopmental disorders occurring later in adulthood like bipolar disorder and schizophrenia, are discussed with regard to impaired melatonin production and circadian rhythms, in particular, sleep-wake rhythms. This article addresses the issue of overlapping symptoms that are commonly observed within these different mental conditions and debates the role of abnormal melatonin production and altered circadian rhythms in the pathophysiology and behavioral expression of these neurodevelopmental disorders.

DNA methylation profiles in individuals with rare, atypical 7q11.23 CNVs correlate with GTF2I and GTF2IRD1 copy number

Williams-Beuren syndrome (WBS) and 7q11.23 duplication syndrome (Dup7) are rare neurodevelopmental disorders caused by deletion and duplication of a 1.5 Mb region that includes at least five genes with a known role in epigenetic regulation. We have shown that CNV of this chromosome segment causes dose-dependent, genome-wide changes in DNA methylation, but the specific genes driving these changes are unknown. We measured genome-wide whole blood DNA methylation in six participants with atypical CNV of 7q11.23 (three with deletions and three with duplications) using the Illumina HumanMethylation450k array and compared their profiles with those from groups of individuals with classic WBS or classic Dup7 and with typically developing (TD) controls. Across the top 1000 most variable positions we found that only the atypical rearrangements that changed the copy number of GTF2IRD1 and/or GTF2I (coding for the TFII-IRD1 and TFII-I proteins) clustered with their respective syndromic cohorts. This finding was supported by results from hierarchical clustering across a selection of differentially methylated CpGs, in addition to pyrosequencing validation. These findings suggest that CNV of the GTF2I genes at the telomeric end of the 7q11.23 interval is a key contributor to the large changes in DNA methylation that are seen in blood DNA from our WBS and Dup7 cohorts, compared to TD controls. Our findings suggest that members of the TFII-I protein family are involved in epigenetic processes that alter DNA methylation on a genome-wide level.

Biallelic GTF2IRD1 variants in brothers with profound neurodevelopmental disorder: A possible novel disorder involving a critical gene for Williams syndrome

GTF2IRD1, a gene on chromosome 7 which encodes a transcription factor, is of significant clinical interest due to its heterozygous loss as part of the classical deletion associated with Williams-Beuren syndrome (WBS). However, biallelic variants in GTF2IRD1 alone as part of an autosomal recessive disease have not been previously reported. Here, we present two full brothers with variants in trans of GTF2IRD1 at c.1231C > T (p.Arg411Trp) and c.2632C > G (p.Leu878Val). A detailed clinical phenotype is described, which includes severe neurodevelopmental disability, facial dysmorphology, and pectus excavatum. Importantly, out of eight full siblings, only these two brothers harboring both variants in trans present with the profound described phenotype. We present the possibility that these brothers represent the identification of a new syndrome characterized by biallelic variants in GTF2IRD1, which may also have important implications for the molecular etiology of WBS.

Atypical deletion of Williams-Beuren syndrome reveals the mechanism of neurodevelopmental disorders

Genes associated with specific neurocognitive phenotypes in Williams–Beuren syndrome are still controversially discussed. This study identified nine patients with atypical deletions out of 111 patients with Williams–Beuren syndrome; these deletions included seven smaller deletions and two larger deletions. One patient had normal neurodevelopment with a deletion of genes on the distal side of the Williams–Beuren syndrome chromosomal region, including GTF2I and GTF2IRD1. However, another patient retained these genes but showed neurodevelopmental abnormalities. By comparing the genotypes and phenotypes of patients with typical and atypical deletions and previous reports in the literature, we hypothesize that the BAZ1B, FZD9, and STX1A genes may play an important role in the neurodevelopment of patients with WBS.

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.

The sociability spectrum: evidence from reciprocal genetic copy number variations

Sociability entails some of the most complex behaviors processed by the central nervous system. It includes the detection, integration, and interpretation of social cues and elaboration of context-specific responses that are quintessentially species-specific. There is an ever-growing accumulation of molecular associations to autism spectrum disorders (ASD), from causative genes to endophenotypes across multiple functional layers; these however, have rarely been put in context with the opposite manifestation featured in hypersociability syndromes. Genetic copy number variations (CNVs) allow to investigate the relationships between gene dosage and its corresponding phenotypes. In particular, CNVs of the 7q11.23 locus, which manifest diametrically opposite social behaviors, offer a privileged window to look into the molecular substrates underlying the developmental trajectories of the social brain. As by definition sociability is studied in humans postnatally, the developmental fluctuations causing social impairments have thus far remained a black box. Here, we review key evidence of molecular players involved at both ends of the sociability spectrum, focusing on genetic and functional associations of neuroendocrine regulators and synaptic transmission pathways. We then proceed to propose the existence of a molecular axis centered around the paradigmatic dosage imbalances at the 7q11.23 locus, regulating networks responsible for the development of social behavior in humans and highlight the key role that neurodevelopmental models from reprogrammed pluripotent cells will play for its understanding.

Social, neurodevelopmental, endocrine, and head size differences associated with atypical deletions in Williams-Beuren syndrome

Williams-Beuren syndrome (WBS) is a multisystem disorder caused by a hemizygous deletion on 7q11.23 encompassing 26-28 genes. An estimated 2-5% of patients have "atypical" deletions, which extend in the centromeric and/or telomeric direction from the WBS critical region. To elucidate clinical differentiators among these deletion types, we evaluated 10 individuals with atypical deletions in our cohort and 17 individuals with similarly classified deletions previously described in the literature. Larger deletions in either direction often led to more severe developmental delays, while deletions containing MAGI2 were associated with infantile spasms and seizures in patients. In addition, head size was notably smaller in those with centromeric deletions including AUTS2. Because children with atypical deletions were noted to be less socially engaged, we additionally sought to determine how atypical deletions relate to social phenotypes. Using the Social Responsiveness Scale-2, raters scored individuals with atypical deletions as having different social characteristics to those with typical WBS deletions (p = .001), with higher (more impaired) scores for social motivation (p = .005) in the atypical deletion group. In recognizing these distinctions, physicians can better identify patients, including those who may already carry a clinical or FISH WBS diagnosis, who may benefit from additional molecular evaluation, screening, and therapy. In addition to the clinical findings, we note mild endocrine findings distinct from those typically seen in WBS in several patients with telomeric deletions that included POR. Further study in additional telomeric deletion cases will be needed to confirm this observation.

Hypothalamic transcriptome of tame and aggressive silver foxes (Vulpes vulpes) identifies gene expression differences shared across brain regions

The underlying neurological events accompanying dog domestication remain elusive. To reconstruct the domestication process in an experimental setting, silver foxes (Vulpes vulpes) have been deliberately bred for tame vs aggressive behaviors for more than 50 generations at the Institute for Cytology and Genetics in Novosibirsk, Russia. The hypothalamus is an essential part of the hypothalamic-pituitary-adrenal axis and regulates the fight-or-flight response, and thus, we hypothesized that selective breeding for tameness/aggressiveness has shaped the hypothalamic transcriptomic profile. RNA-seq analysis identified 70 differentially expressed genes (DEGs). Seven of these genes, DKKL1, FBLN7, NPL, PRIMPOL, PTGRN, SHCBP1L and SKIV2L, showed the same direction expression differences in the hypothalamus, basal forebrain and prefrontal cortex. The genes differentially expressed across the three tissues are involved in cell division, differentiation, adhesion and carbohydrate processing, suggesting an association of these processes with selective breeding. Additionally, 159 transcripts from the hypothalamus demonstrated differences in the abundance of alternative spliced forms between the tame and aggressive foxes. Weighted gene coexpression network analyses also suggested that gene modules in hypothalamus were significantly associated with tame vs aggressive behavior. Pathways associated with these modules include signal transduction, interleukin signaling, cytokine-cytokine receptor interaction and peptide ligand-binding receptors (eg, G-protein coupled receptor [GPCR] ligand binding). Current studies show the selection for tameness vs aggressiveness in foxes is associated with unique hypothalamic gene profiles partly shared with other brain regions and highlight DEGs involved in biological processes such as development, differentiation and immunological responses. The role of these processes in fox and dog domestication remains to be determined.

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).

The chromatin basis of neurodevelopmental disorders: Rethinking dysfunction along the molecular and temporal axes

The complexity of the human brain emerges from a long and finely tuned developmental process orchestrated by the crosstalk between genome and environment. Vis à vis other species, the human brain displays unique functional and morphological features that result from this extensive developmental process that is, unsurprisingly, highly vulnerable to both genetically and environmentally induced alterations. One of the most striking outcomes of the recent surge of sequencing-based studies on neurodevelopmental disorders (NDDs) is the emergence of chromatin regulation as one of the two domains most affected by causative mutations or Copy Number Variations besides synaptic function, whose involvement had been largely predicted for obvious reasons. These observations place chromatin dysfunction at the top of the molecular pathways hierarchy that ushers in a sizeable proportion of NDDs and that manifest themselves through synaptic dysfunction and recurrent systemic clinical manifestation. Here we undertake a conceptual investigation of chromatin dysfunction in NDDs with the aim of systematizing the available evidence in a new framework: first, we tease out the developmental vulnerabilities in human corticogenesis as a structuring entry point into the causation of NDDs; second, we provide a much needed clarification of the multiple meanings and explanatory frameworks revolving around "epigenetics", highlighting those that are most relevant for the analysis of these disorders; finally we go in-depth into paradigmatic examples of NDD-causing chromatin dysregulation, with a special focus on human experimental models and datasets.

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.

A postmortem stereological study of the amygdala in Williams syndrome

Perturbations to the amygdala have been observed in neurological disorders characterized by abnormalities in social behavior, such as autism and schizophrenia. Here, we quantitatively examined the amygdala in the postmortem human brains of male and female individuals diagnosed with Williams Syndrome (WS), a neurodevelopmental disorder caused by a well-defined deletion of ~ 26 genes, and accompanied by a consistent behavioral profile that includes profound hypersociability. Using unbiased stereological sampling, we estimated nucleus volume, number of neurons, neuron density, and neuron soma area in four major amygdaloid nuclei- the lateral nucleus, basal nucleus, accessory basal nucleus, and central nucleus- in a sample of five adult and two infant WS brains and seven age-, sex- and hemisphere-matched typically developing control (TD) brains. Boundaries of the four nuclei examined were drawn on Nissl-stained coronal sections as four separate regions of interest for data collection. We found that the lateral nucleus contains significantly more neurons in WS compared to TD. WS and TD do not demonstrate significant differences in neuron number in the basal, accessory basal, or central nuclei, and there are no significant differences between WS and TD in nuclei volume, neuron density, and neuron soma area in any of the four nuclei. A similarly designed study reported a decrease in lateral nucleus neuron number in autism, mirroring the opposing extremes of the two disorders in the social domain. These results suggest that the number of neurons in the lateral nucleus may contribute to pathological disturbances in amygdala function and sociobehavioral phenotype.

The Williams syndrome prosociality gene GTF2I mediates oxytocin reactivity and social anxiety in a healthy population

The neurohormone oxytocin plays a central role in human social behaviour and cognition, and oxytocin dysregulation may contribute to psychiatric disorders. However, genetic factors influencing individual variation in the oxytocinergic system remain poorly understood. We genotyped 169 healthy adults for a functional polymorphism in GTF2I (general transcription factor II-I), a gene associated with high prosociality and reduced social anxiety in Williams syndrome, a condition reported to involve high oxytocin levels and reactivity. Participants' salivary oxytocin levels were measured before and after watching a validated empathy-inducing video. Oxytocin reactivity, defined as pre- to post-video percentage change in salivary oxytocin, varied substantially and significantly between individuals with different GTF2I genotypes, with, additionally, a trend towards an interaction between genotype and sex. Individuals with more oxytocin-reactive genotypes also reported significantly lower social anxiety. These findings suggest a model whereby GTF2I has a continuum of effects on human sociality, from the extreme social phenotypes and oxytocin dysregulation associated with gene deletion in Williams syndrome, to individual differences in oxytocin reactivity and sociality associated with common polymorphisms in healthy populations.

De Novo Mutations in YWHAG Cause Early-Onset Epilepsy

Massively parallel sequencing has revealed many de novo mutations in the etiology of developmental and epileptic encephalopathies (EEs), highlighting their genetic heterogeneity. Additional candidate genes have been prioritized in silico by their co-expression in the brain. Here, we evaluate rare coding variability in 20 candidates nominated with the use of a reference gene set of 51 established EE-associated genes. Variants within the 20 candidate genes were extracted from exome-sequencing data of 42 subjects with EE and no previous genetic diagnosis. We identified 7 rare non-synonymous variants in 7 of 20 genes and performed Sanger sequence validation in affected probands and parental samples. De novo variants were found only in SLC1A2 (aka EAAT2 or GLT1) (c.244G>A [p.Gly82Arg]) and YWHAG (aka 14-3-3γ) (c.394C>T [p.Arg132Cys]), highlighting the potential cause of EE in 5% (2/42) of subjects. Seven additional subjects with de novo variants in SLC1A2 (n = 1) and YWHAG (n = 6) were subsequently identified through online tools. We identified a highly significant enrichment of de novo variants in YWHAG, establishing their role in early-onset epilepsy, and we provide additional support for the prior assignment of SLC1A2. Hence, in silico modeling of brain co-expression is an efficient method for nominating EE-associated genes to further elucidate the disorder's etiology and genotype-phenotype correlations.

Structural variants in genes associated with human Williams-Beuren syndrome underlie stereotypical hypersociability in domestic dogs

Although considerable progress has been made in understanding the genetic basis of morphologic traits (for example, body size and coat color) in dogs and wolves, the genetic basis of their behavioral divergence is poorly understood. An integrative approach using both behavioral and genetic data is required to understand the molecular underpinnings of the various behavioral characteristics associated with domestication. We analyze a 5-Mb genomic region on chromosome 6 previously found to be under positive selection in domestic dog breeds. Deletion of this region in humans is linked to Williams-Beuren syndrome (WBS), a multisystem congenital disorder characterized by hypersocial behavior. We associate quantitative data on behavioral phenotypes symptomatic of WBS in humans with structural changes in the WBS locus in dogs. We find that hypersociability, a central feature of WBS, is also a core element of domestication that distinguishes dogs from wolves. We provide evidence that structural variants in GTF2I and GTF2IRD1, genes previously implicated in the behavioral phenotype of patients with WBS and contained within the WBS locus, contribute to extreme sociability in dogs. This finding suggests that there are commonalities in the genetic architecture of WBS and canine tameness and that directional selection may have targeted a unique set of linked behavioral genes of large phenotypic effect, allowing for rapid behavioral divergence of dogs and wolves, facilitating coexistence with humans.

Role of Genetics in the Etiology of Autistic Spectrum Disorder: Towards a Hierarchical Diagnostic Strategy

Progress in epidemiological, molecular and clinical genetics with the development of new techniques has improved knowledge on genetic syndromes associated with autism spectrum disorder (ASD). The objective of this article is to show the diversity of genetic disorders associated with ASD (based on an extensive review of single-gene disorders, copy number variants, and other chromosomal disorders), and consequently to propose a hierarchical diagnostic strategy with a stepwise evaluation, helping general practitioners/pediatricians and child psychiatrists to collaborate with geneticists and neuropediatricians, in order to search for genetic disorders associated with ASD. The first step is a clinical investigation involving: (i) a child psychiatric and psychological evaluation confirming autism diagnosis from different observational sources and assessing autism severity; (ii) a neuropediatric evaluation examining neurological symptoms and developmental milestones; and (iii) a genetic evaluation searching for dysmorphic features and malformations. The second step involves laboratory and if necessary neuroimaging and EEG studies oriented by clinical results based on clinical genetic and neuropediatric examinations. The identification of genetic disorders associated with ASD has practical implications for diagnostic strategies, early detection or prevention of co-morbidity, specific treatment and follow up, and genetic counseling.

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.

Reframing autism as a behavioral syndrome and not a specific mental disorder: Implications of genetic and phenotypic heterogeneity

Clinical and molecular genetics have advanced current knowledge on genetic disorders associated with autism. A review of diverse genetic disorders associated with autism is presented and for the first time discussed extensively with regard to possible common underlying mechanisms leading to a similar cognitive-behavioral phenotype of autism. The possible role of interactions between genetic and environmental factors, including epigenetic mechanisms, is in particular examined. Finally, the pertinence of distinguishing non-syndromic autism (isolated autism) from syndromic autism (autism associated with genetic disorders) will be reconsidered. Given the high genetic and etiological heterogeneity of autism, autism can be viewed as a behavioral syndrome related to known genetic disorders (syndromic autism) or currently unknown disorders (apparent non-syndromic autism), rather than a specific categorical mental disorder. It highlights the need to study autism phenotype and developmental trajectory through a multidimensional, non-categorical approach with multivariate analyses within autism spectrum disorder but also across mental disorders, and to conduct systematically clinical genetic examination searching for genetic disorders in all individuals (children but also adults) with autism.

Neuron density is decreased in the prefrontal cortex in Williams syndrome

Williams Syndrome (WS) is a rare neurodevelopmental disorder associated with a hemideletion in chromosome 7, which manifests a distinct behavioral phenotype characterized by a hyperaffiliative social drive, in striking contrast to the social avoidance behaviors that are common in Autism Spectrum Disorder (ASD). MRI studies have observed structural and functional abnormalities in WS cortex, including the prefrontal cortex (PFC), a region implicated in social cognition. This study utilizes the Bellugi Williams Syndrome Brain Collection, a unique resource that comprises the largest WS postmortem brain collection in existence, and is the first to quantitatively examine WS PFC cytoarchitecture. We measured neuron density in layers II/III and V/VI of five cortical areas: PFC areas BA 10 and BA 11, primary motor BA 4, primary somatosensory BA 3, and visual area BA 18 in six matched pairs of WS and typically developing (TD) controls. Neuron density in PFC was lower in WS relative to TD, with layers V/VI demonstrating the largest decrease in density, reaching statistical significance in BA 10. In contrast, BA 3 and BA 18 demonstrated a higher density in WS compared to TD, although this difference was not statistically significant. Neuron density in BA 4 was similar in WS and TD. While other cortical areas were altered in WS, prefrontal areas appeared to be most affected. Neuron density is also altered in the PFC of individuals with ASD. Together these findings suggest that the PFC is targeted in neurodevelopmental disorders associated with sociobehavioral alterations. Autism Res 2017, 10: 99-112. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

A human neurodevelopmental model for Williams syndrome

Williams syndrome is a genetic neurodevelopmental disorder characterized by an uncommon hypersociability and a mosaic of retained and compromised linguistic and cognitive abilities. Nearly all clinically diagnosed individuals with Williams syndrome lack precisely the same set of genes, with breakpoints in chromosome band 7q11.23 (refs 1-5). The contribution of specific genes to the neuroanatomical and functional alterations, leading to behavioural pathologies in humans, remains largely unexplored. Here we investigate neural progenitor cells and cortical neurons derived from Williams syndrome and typically developing induced pluripotent stem cells. Neural progenitor cells in Williams syndrome have an increased doubling time and apoptosis compared with typically developing neural progenitor cells. Using an individual with atypical Williams syndrome, we narrowed this cellular phenotype to a single gene candidate, frizzled 9 (FZD9). At the neuronal stage, layer V/VI cortical neurons derived from Williams syndrome were characterized by longer total dendrites, increased numbers of spines and synapses, aberrant calcium oscillation and altered network connectivity. Morphometric alterations observed in neurons from Williams syndrome were validated after Golgi staining of post-mortem layer V/VI cortical neurons. This model of human induced pluripotent stem cells fills the current knowledge gap in the cellular biology of Williams syndrome and could lead to further insights into the molecular mechanism underlying the disorder and the human social brain.

Neurobiology of social behavior abnormalities in autism and Williams syndrome

Social behavior is a basic behavior mediated by multiple brain regions and neural circuits, and is crucial for the survival and development of animals and humans. Two neuropsychiatric disorders that have prominent social behavior abnormalities are autism spectrum disorders (ASD), which is characterized mainly by hyposociability, and Williams syndrome (WS), whose subjects exhibit hypersociability. Here we review the unique properties of social behavior in ASD and WS, and discuss the major theories in social behavior in the context of these disorders. We conclude with a discussion of the research questions needing further exploration to enhance our understanding of social behavior abnormalities.

Array CGH - A Powerful Tool in Molecular Diagnostic of Pathogenic Microdeletions - Williams-Beuren Syndrome - A Case Report

ABSTRACT: Williams-Beuren syndrome (WBS) (OMIM 194050) is caused by interstitial deletions or duplications of the 7q11.23 chromosomal region and characterised through a complex phenotype. We described a case diagnosed clinically and genetically confirmed through aCGH. Genetic assessment identified three microdeletions with a total size of 1.35 Mb located at 7q11.23. The deleted regions encompasses more than 30 genes including several protein coding genes such as ELN, LIMK1, FZDS, WBSCR22, WBSCR27, WBSCR28, STX1A, CLDN3, CLDN4, LAT2, ABHD11 or EIF4H .

Copy number variation in CEP57L1 predisposes to congenital absence of bilateral ACL and PCL ligaments

Background

Absence of the anterior (ACL) or posterior cruciate ligament (PCL) are rare congenital malformations that result in knee joint instability, with a prevalence of 1.7 per 100,000 live births and can be associated with other lower-limb abnormalities such as ACL agnesia and absence of the menisci of the knee. While a few cases of absence of ACL/PCL are reported in the literature, a number of large familial case series of related conditions such as ACL agnesia suggest a potential underlying monogenic etiology. We performed whole exome sequencing of a family with two individuals affected by ACL/PCL.

Results

We identified copy number variation (CNV) deletion impacting the exon sequences of CEP57L1, present in the affected mother and her affected daughter based on the exome sequencing data. The deletion was validated using quantitative PCR (qPCR), and the gene was confirmed to be expressed in ACL ligament tissue. Interestingly, we detected reduced expression of CEP57L1 in Epstein–Barr virus (EBV) cells from the two patients in comparison with healthy controls. Evaluation of 3D protein structure showed that the helix-binding sites of the protein remain intact with the deletion, but other functional binding sites related to microtubule attachment are missing. The specificity of the CNV deletion was confirmed by showing that it was absent in ~700 exome sequencing samples as well as in the database of genomic variations (DGV), a database containing large numbers of annotated CNVs from previous scientific reports.

Conclusions

We identified a novel CNV deletion that was inherited through an autosomal dominant transmission from an affected mother to her affected daughter, both of whom suffered from the absence of the anterior and posterior cruciate ligaments of the knees.

Electronic supplementary material

The online version of this article (doi:10.1186/s40246-015-0053-z) contains supplementary material, which is available to authorized users.

De novo variants in sporadic cases of childhood onset schizophrenia

Childhood-onset schizophrenia (COS), defined by the onset of illness before age 13 years, is a rare severe neurodevelopmental disorder of unknown etiology. Recently, sequencing studies have identified rare, potentially causative de novo variants in sporadic cases of adult-onset schizophrenia and autism. In this study, we performed exome sequencing of 17 COS trios in order to test whether de novo variants could contribute to this disease. We identified 20 de novo variants in 17 COS probands, which is consistent with the de novo mutation rate reported in the adult form of the disease. Interestingly, the missense de novo variants in COS have a high likelihood for pathogenicity and were enriched for genes that are less tolerant to variants. Among the genes found disrupted in our study, SEZ6, RYR2, GPR153, GTF2IRD1, TTBK1 and ITGA6 have been previously linked to neuronal function or to psychiatric disorders, and thus may be considered as COS candidate genes.

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.

Intracisternal Gtf2i Gene Therapy Ameliorates Deficits in Cognition and Synaptic Plasticity of a Mouse Model of Williams-Beuren Syndrome

Williams-Beuren syndrome (WBS) is a neurodevelopmental disorder caused by a heterozygous deletion of 26-28 genes at chromosome band 7q11.23. Haploinsufficiency at GTF2I has been shown to play a major role in the neurobehavioral phenotype. By characterizing the neuronal architecture in four animal models with intragenic, partial, and complete deletions of the WBS critical interval (ΔGtf2i(+/-), ΔGtf2i( -/-), PD, and CD), we clarify the involvement of Gtf2i in neurocognitive features. All mutant mice showed hypersociability, impaired motor learning and coordination, and altered anxiety-like behavior. Dendritic length was decreased in the CA1 of ΔGtf2i(+/-), ΔGtf2i ( -/-), and CD mice. Spine density was reduced, and spines were shorter in ΔGtf2i ( -/-), PD, and CD mice. Overexpression of Pik3r1 and downregulation of Bdnf were observed in ΔGtf2i(+/-), PD, and CD mice. Intracisternal Gtf2i-gene therapy in CD mice using adeno-associated virus resulted in increased mGtf2i expression and normalization of Bdnf levels, along with beneficial effects in motor coordination, sociability, and anxiety, despite no significant changes in neuronal architecture. Our findings further indicate that Gtf2i haploinsufficiency plays an important role in the neurodevelopmental and cognitive abnormalities of WBS and that it is possible to rescue part of this neurocognitive phenotype by restoring Gtf2i expression levels in specific brain areas.

Application of Whole Exome Sequencing in Six Families with an Initial Diagnosis of Autosomal Dominant Retinitis Pigmentosa: Lessons Learned

This study aimed to identify the genetics underlying dominant forms of inherited retinal dystrophies using whole exome sequencing (WES) in six families extensively screened for known mutations or genes. Thirty-eight individuals were subjected to WES. Causative variants were searched among single nucleotide variants (SNVs) and insertion/deletion variants (indels) and whenever no potential candidate emerged, copy number variant (CNV) analysis was performed. Variants or regions harboring a candidate variant were prioritized and segregation of the variant with the disease was further assessed using Sanger sequencing in case of SNVs and indels, and quantitative PCR (qPCR) for CNVs. SNV and indel analysis led to the identification of a previously reported mutation in PRPH2. Two additional mutations linked to different forms of retinal dystrophies were identified in two families: a known frameshift deletion in RPGR, a gene responsible for X-linked retinitis pigmentosa and p.Ser163Arg in C1QTNF5 associated with Late-Onset Retinal Degeneration. A novel heterozygous deletion spanning the entire region of PRPF31 was also identified in the affected members of a fourth family, which was confirmed with qPCR. This study allowed the identification of the genetic cause of the retinal dystrophy and the establishment of a correct diagnosis in four families, including a large heterozygous deletion in PRPF31, typically considered one of the pitfalls of this method. Since all findings in this study are restricted to known genes, we propose that targeted sequencing using gene-panel is an optimal first approach for the genetic screening and that once known genetic causes are ruled out, WES might be used to uncover new genes involved in inherited retinal dystrophies.

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.

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.

Gene × Environment interactions in autism spectrum disorders: role of epigenetic mechanisms

Several studies support currently the hypothesis that autism etiology is based on a polygenic and epistatic model. However, despite advances in epidemiological, molecular and clinical genetics, the genetic risk factors remain difficult to identify, with the exception of a few chromosomal disorders and several single gene disorders associated with an increased risk for autism. Furthermore, several studies suggest a role of environmental factors in autism spectrum disorders (ASD). First, arguments for a genetic contribution to autism, based on updated family and twin studies, are examined. Second, a review of possible prenatal, perinatal, and postnatal environmental risk factors for ASD are presented. Then, the hypotheses are discussed concerning the underlying mechanisms related to a role of environmental factors in the development of ASD in association with genetic factors. In particular, epigenetics as a candidate biological mechanism for gene × environment interactions is considered and the possible role of epigenetic mechanisms reported in genetic disorders associated with ASD is discussed. Furthermore, the example of in utero exposure to valproate provides a good illustration of epigenetic mechanisms involved in ASD and innovative therapeutic strategies. Epigenetic remodeling by environmental factors opens new perspectives for a better understanding, prevention, and early therapeutic intervention of ASD.

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.

δ ENaC: a novel divergent amiloride-inhibitable sodium channel

The fourth subunit of the epithelial sodium channel, termed delta subunit (δ ENaC), was cloned in human and monkey. Increasing evidence shows that this unique subunit and its splice variants exhibit biophysical and pharmacological properties that are divergent from those of α ENaC channels. The widespread distribution of epithelial sodium channels in both epithelial and nonepithelial tissues implies a range of physiological functions. The altered expression of SCNN1D is associated with numerous pathological conditions. Genetic studies link SCNN1D deficiency with rare genetic diseases with developmental and functional disorders in the brain, heart, and respiratory systems. Here, we review the progress of research on δ ENaC in genomics, biophysics, proteomics, physiology, pharmacology, and clinical medicine.

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.

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.

Detection of deletions at 7q11.23 in Williams-Beuren syndrome by polymorphic markers

INTRODUCTION

Williams-Beuren syndrome (WBS; OMIM 194050) is caused by a hemizygous contiguous gene microdeletion at 7q11.23. Supravalvular aortic stenosis, mental retardation, overfriendliness, and ocular and renal abnormalities comprise typical symptoms in WBS. Although fluorescence in situ hybridization is widely used for diagnostic confirmation, microsatellite DNA markers are considered highly informative and easily manageable.

OBJECTIVES

This study aimed to test the microsatellite markers for the diagnosis of Williams-Beuren syndrome, to determine the size and parental origin of microdeletion, compare the clinical characteristics between patients with different sizes of the deletion and parental origin.

METHODS

We studied 97 patients with clinical diagnosis of Williams-Beuren syndrome using five microsatellite markers: D7S1870, D7S489, D7S613, D7S2476 and D7S489_A.

RESULTS AND DISCUSSION

Using five markers together, the result was informative in all patients. The most informative marker was D7S1870 (78.4%), followed by D7S613 (75.3%), D7S489 (70.1%) and D7S2476 (62.9%). The microdeletion was present in 84 (86.6%) patients and absent in 13 (13.4%) patients. Maternal deletions were found in 52.4% of patients and paternal deletions in 47.6% of patients. The observed size of deletions was 1.55 Mb in 76/ 84 patients (90.5%) and 1.84 Mb in 8/84 patients (9.5%). SVAS as well as ocular and urinary abnormalities were more frequent in the patients with a deletion. There were no clinical differences in relation to either the size or parental origin of the deletion.

CONCLUSION

Using these five selected microsatellite markers was informative in all patients, thus can be considered an alternative method for molecular diagnosis in Williams-Beuren syndrome.