TFII-I, a candidate gene for Williams syndrome cognitive profile: parallels between regional expression in mouse brain and human phenotype

Loss of GTF2I promotes neuronal apoptosis and synaptic reduction in human cellular models of neurodevelopment

Individuals with Williams syndrome (WS), a neurodevelopmental disorder caused by hemizygous loss of 26-28 genes at 7q11.23, characteristically portray a hypersocial phenotype. Copy-number variations and mutations in one of these genes, GTF2I, are associated with altered sociality and are proposed to underlie hypersociality in WS. However, the contribution of GTF2I to human neurodevelopment remains poorly understood. Here, human cellular models of neurodevelopment, including neural progenitors, neurons, and three-dimensional cortical organoids, are differentiated from CRISPR-Cas9-edited GTF2I-knockout (GTF2I-KO) pluripotent stem cells to investigate the role of GTF2I in human neurodevelopment. GTF2I-KO progenitors exhibit increased proliferation and cell-cycle alterations. Cortical organoids and neurons demonstrate increased cell death and synaptic dysregulation, including synaptic structural dysfunction and decreased electrophysiological activity on a multielectrode array. Our findings suggest that changes in synaptic circuit integrity may be a prominent mediator of the link between alterations in GTF2I and variation in the phenotypic expression of human sociality.

Neuronal Gtf2i deletion alters mitochondrial and autophagic properties

Gtf2i encodes the general transcription factor II-I (TFII-I), with peak expression during pre-natal and early post-natal brain development stages. Because these stages are critical for proper brain development, we studied at the single-cell level the consequences of Gtf2i's deletion from excitatory neurons, specifically on mitochondria. Here we show that Gtf2i's deletion resulted in abnormal morphology, disrupted mRNA related to mitochondrial fission and fusion, and altered autophagy/mitophagy protein expression. These changes align with elevated reactive oxygen species levels, illuminating Gtf2i's importance in neurons mitochondrial function. Similar mitochondrial issues were demonstrated by Gtf2i heterozygous model, mirroring the human condition in Williams syndrome (WS), and by hemizygous neuronal Gtf2i deletion model, indicating Gtf2i's dosage-sensitive role in mitochondrial regulation. Clinically relevant, we observed altered transcript levels related to mitochondria, hypoxia, and autophagy in frontal cortex tissue from WS individuals. Our study reveals mitochondrial and autophagy-related deficits shedding light on WS and other Gtf2i-related disorders.

The ALOXE3 gene variants from patients with Dravet syndrome decrease gene expression and enzyme activity

Aberrant expression or dysfunction of a number of genes in the brain contributes to epilepsy, a common neurological disorder characterized by recurrent seizures. Local overexpression of arachidonate lipoxygenase 3 (ALOXE3), a key enzyme for arachidonic acid (AA) metabolic pathway, alleviates seizure severities. However, the relationship between the ALOXE3 gene mutation and epilepsy has not been reported until now. Here we firstly characterized the promoter of human ALOXE3 gene and found that the ALOXE3 promoter could drive luciferase gene expression in the human HEK-293 and SH-SY5Y cells. We then screened the ALOXE3 promoter region and all coding exons from those patients with Dravet syndrome and identified 5 variants c.-163T > C, c.-50C > G, c.-37G > A, c. + 228G > A and c. + 290G > T in the promoter region and one missense variant c.1939A > G (p.I647 V) in the exon. Of these variants in the promoter region, only -50C > G was a novel variant located on the transcriptional factor NFII-I binding element. Luciferase reporter gene analyses indicated that the c.-50C > G could decrease gene expression by preventing the TFII-I's binding. In addition, the variant p.I647 V was conserved among all analyzed species and located within the ALOXE3 functional domain for catalyzing its substrate. In cultured cell lines, overexpression of ALOXE3 significantly decreased the cellular AA levels and overexpression of ALOXE3-I647 V could restore the AA levels, suggesting that the p.I647 V mutant led to a decrease in enzyme activity. Taken together, the present study proposes that the identified ALOXE3 variants potentially contribute to the AA-pathway-mediated epileptogenesis, which should provide a novel avenue for clinical diagnosis of epilepsy.

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

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

Intrauterine phenotype features of fetuses with Williams-Beuren syndrome and literature review

Williams-Beuren syndrome (WBS) is a well-defined multisystem chromosomal disorder that is caused by a chromosome 7q11.23 region heterozygous deletion. We explored prenatal diagnosis of WBS by ultrasound as well as multiple genetic methods to characterize the structural variants of WBS prenatally. Expanded noninvasive prenatal testing (NIPT-plus) was elected as a regular prenatal advanced screen for risk assessments of fetal chromosomal aneuploidy and genome-wide microdeletion/microduplication syndromes at the first trimester. At the second and three trimester, seven prenatal cases of WBS were evaluated for the indication of the invasive testing, the ultrasound features, cytogenetic, single-nucleotide polymorphism array (SNP array), and fluorescent quantitative PCR (QF-PCR) results. The NIPT-plus results for seven fetuses were low risk. All cryptic aberrations were detected by the SNP array as karyotyping analyses were negative. Subsequently, QF-PCR further confirmed the seven deletions. Combining our cases with 10 prenatal cases from the literature, the most common sonographic features were intrauterine growth retardation (82.35%, 14/17) and congenital cardiovascular abnormalities (58.82%, 10/17). The manifestations of cardiovascular defects mainly involve supravalvar aortic stenosis (40%, 4/10), ventricular septal defect (30%, 3/10), aortic coarctation (20%, 2/10), and peripheral pulmonary artery stenosis (20%, 2/10). To the best of our knowledge, this is the first largest prenatal study of WBS cases with detailed molecular analysis. Aortic coarctation combined with persistent left superior vena cava and right aortic arch cardiovascular defects were first reported in prenatal WBS cases by our study.

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.

Modeling Williams syndrome with induced pluripotent stem cells

The development of induced pluripotent stem cells (iPSCs) like never before has opened novel opportunity to study diseases in relevant cell types. In our recent study, Williams syndrome (WS), a rare genetic neurodevelopmental disorder, that is caused by hemizygous deletion of 25-28 genes on chromosome 7, is of interest because of its unique cognitive and social profiles. Little is known about haploinsufficiency effect of those deleted genes on molecular and cellular phenotypes at the neural level due to the lack of relevant human cellular model. Using the cellular reprogramming approach, we reported that WS iPSC-derived neural progenitor cells (NPCs) has increased apoptosis and therefore increased doubling time, which could be rescued by complementation of frizzled 9, one of the genes typically deleted in WS. Moreover, WS iPSC-derived CTIP2-positive pyramidal neurons exhibit morphologic alterations including longer total dendrites and increasing dendritic spine number. In addition, WS iPSC-derived neurons show an increase in calcium transient frequency and synchronized activity likely due to increased number of dendritic spines and synapses. Our work integrated cross-level data from genetics to behavior of WS individuals and revealed altered cellular phenotypes in WS human NPCs and neurons that could be validated in other model systems such as magnetic resonance imaging (MRI) in live subjects and postmortem brain tissues.

TRPC Channels and Mental Disorders

Transient receptor potential canonical (TRPC) channels mediate the influx of different types of cations through the cell membrane and are involved in many functions of the organism. Evidences of involvement of TRPC channels in neuronal development suggest that this family of proteins might play a role in certain neurological disorders. As reported, knockout mice for different TRPC channels show alterations in neuronal morphological and functional parameters, with behavioral abnormalities, such as in exploratory and social behaviors. Although mutations in TRPC channels could be related to mental/neurological disorders, there are only a few cases reported in literature, indicating that this correlation should be further explored. Nonetheless, other functional evidences support the implication of these channels in neurological diseases. In this chapter, we summarize the main findings relating TRPC channels to neurological disorders, such as autism spectrum disorders, bipolar disorder, and intellectual disability among others.

Cognitive-behavioral phenotypes of Williams syndrome are associated with genetic variation in the GTF2I gene, in a healthy population

Background

Individuals with Williams syndrome, a neurogenetic condition caused by deletion of a set of genes at chromosomal location 7q11.23, exhibit a remarkable suite of traits including hypersociality with high, nonselective friendliness and low social anxiety, expressive language relatively well-developed but under-developed social-communication skills overall, and reduced visual-spatial abilities. Deletions and duplications of the Williams-syndrome region have also been associated with autism, and with schizophrenia, two disorders centrally involving social cognition. Several lines of evidence have linked the gene GTF2I (General Transcription Factor IIi) with the social phenotypes of Williams syndrome, but a role for this gene in sociality within healthy populations has yet to be investigated.

Results

We genotyped a large set of healthy individuals for two single-nucleotide polymorphisms in the GTF2I gene that have recently been significantly associated with autism, and thus apparently exhibit functional effects on autism-related social phenotypes. GTF2I genotypes for these SNPs showed highly significant association with low social anxiety combined with reduced social-communication abilities, which represents a metric of the Williams-syndrome cognitive profile as described from previous studies.

Conclusions

These findings implicate the GTF2I gene in the neurogenetic basis of social communication and social anxiety, both in Williams syndrome and among individuals in healthy populations.

GTF2IRD2 from the Williams-Beuren critical region encodes a mobile-element-derived fusion protein that antagonizes the action of its related family members

GTF2IRD2 belongs to a family of transcriptional regulators (including TFII-I and GTF2IRD1) that are responsible for many of the key features of Williams-Beuren syndrome (WBS). Sequence evidence suggests that GTF2IRD2 arose in eutherian mammals by duplication and divergence from the gene encoding TFII-I. However, in GTF2IRD2, most of the C-terminal domain has been lost and replaced by the domesticated remnant of an in-frame hAT-transposon mobile element. In this first experimental analysis of function, we show that transgenic expression of each of the three family members in skeletal muscle causes significant fiber type shifts, but the GTF2IRD2 protein causes an extreme shift in the opposite direction to the two other family members. Mating of GTF2IRD1 and GTF2IRD2 mice restores the fiber type balance, indicating an antagonistic relationship between these two paralogs. In cells, GTF2IRD2 localizes to cytoplasmic microtubules and discrete speckles in the nuclear periphery. We show that it can interact directly with TFII-Iβ and GTF2IRD1, and upon co-transfection changes the normal distribution of these two proteins into a punctate nuclear pattern typical of GTF2IRD2. These data suggest that GTF2IRD2 has evolved as a regulator of GTF2IRD1 and TFII-I; inhibiting their function by direct interaction and sequestration into inactive nuclear zones.

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.

Expression of the transcription factor, TFII-I, during post-implantation mouse embryonic development

BACKGROUND

General transcription factor (TFII-I) is a multi-functional transcription factor encoded by the Gtf2i gene, that has been demonstrated to regulate transcription of genes critical for development. Because of the broad range of genes regulated by TFII-I as well as its potential role in a significant neuro-developmental disorder, developing a comprehensive expression profile is critical to the study of this transcription factor. We sought to define the timing and pattern of expression of TFII-I in post-implantation embryos at a time during which many putative TFII-I target genes are expressed.

FINDINGS

Antibodies to the N-terminus of TFII-I were used to probe embryonic mouse sections. TFII-I protein is widely expressed in the developing embryo. TFII-I is expressed throughout the period from E8-E16. However, within this period there are striking shifts in localization from cytoplasmic predominant to nuclear. TFII-I expression varies in both a spatial and temporal fashion. There is extensive expression in neural precursors at E8. This expression persists at later stages. TFII-I is expressed in developing lung, heart and gut structures. There is no evidence of isoform specific expression. Available data regarding expression patterns at both an RNA and protein level throughout development are also comprehensively reviewed.

CONCLUSIONS

Our immunohistochemical studies of the temporal and spatial expression patterns of TFII-I in mouse embryonic sections are consistent with the hypothesis that hemizygous deletion of GTF2I in individuals with Williams-Beuren Syndrome contributes to the distinct cognitive and physiological symptoms associated with the disorder.

William's syndrome: gene expression is related to parental origin and regional coordinate control

William's syndrome (WS) features a spectrum of neurocognitive and behavioral abnormalities due to a rare 1.5 MB deletion that includes about 24-28 genes on chromosome band 7q11.23. Study of the expression of these genes from the single normal copy provides an opportunity to elucidate the genetic and epigenetic controls on these genes as well as their roles in both WS and normal brain development and function. We used quantitative RT-PCR to determine the transcriptional level of 14 WS gene markers in a cohort of 77 persons with WS and 48 normal controls. Results reported here: (1) show that the expression of the genes deleted in WS is decreased in some but not all cases, (2) demonstrate that the parental origin of the deletion contributes to the level of expression of GTF2I independently of age and gender and (3) indicate that the correlation of expression between GTF2I and some other genes in the WS region differs in WS subjects and normal controls, which in turn points toward a regulatory role for this gene. Interspecies comparisons suggest GTF2I may play a key role in normal brain development.

Alternative splicing and promoter use in TFII-I genes

TFII-I proteins are ubiquitously expressed transcriptional factors involved in both basal transcription and signal transduction activation or repression. TFII-I proteins are detected as early as at two-cell stage and exhibit distinct and dynamic expression patterns in developing embryos as well as mark regional variation in the adult mouse brain. Analysis of atypical small and rare chromosomal deletions at 7q11.23 points to TFII-I genes (GTF2I and GTF2IRD1) as the prime candidates responsible for craniofacial and cognitive abnormalities in the Williams-Beuren syndrome. TFII-I genes are often subjected to alternative splicing, which generates isoforms that show different activities and play distinct biological roles. The coding regions of TFII-I genes are composed of more than 30 exons and are well conserved among vertebrates. However, their 5' untranslated regions are not as well conserved and all poorly characterized. In the present work, we analyzed promoter regions of TFII-I genes and described their additional exons, as well as tested tissue specificity of both previously reported and novel alternatively spliced isoforms. Our comprehensive analysis leads to further elucidation of the functional heterogeneity of TFII-I proteins, provides hints on search for regulatory pathways governing their expression, and opens up possibilities for examining the effect of different haplotypes on their promoter functions.

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.

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.

GTF2IRD1 regulates transcription by binding an evolutionarily conserved DNA motif ‘GUCE’

GTF2IRD1 is a member of a family of transcription factors whose defining characteristic is varying numbers of a helix-loop-helix like motif, the I-repeat. Here, we present functional analysis of human GTF2IRD1 in regulation of three genes (HOXC8, GOOSECOID and TROPONIN I(SLOW)). We define a regulatory motif (GUCE-GTF2IRD1 Upstream Control Element) common to all three genes. GUCE is bound in vitro by domain I-4 of GTF2IRD1 and mediates transcriptional regulation by GTF2IRD1 in vivo. Definition of this site will assist in identification of other downstream targets of GTF2IRD1 and elucidation of its role in the human developmental disorder Williams-Beuren syndrome.

Expression profiling of BEN regulated genes in mouse embryonic fibroblasts

BEN is a member of the TFII-I family of helix-loop-helix transcription factors. Both TFII-I and BEN are involved in gene regulation through interactions with tissue-specific transcription factors and chromatin remodeling complexes. Identification of the downstream target genes of TFII-I proteins is critical in delineating the regulatory effects of these proteins. In this study, we conducted a microarray analysis to determine gene expression alterations following the overexpression of BEN in primary mouse embryonic fibroblasts (MEFs). We found the BEN-dependent modulation in the expression of large groups of genes representing a wide variety of functional categories including genes important in the immune response, cell cycle, transcriptional regulation and cell signaling. A set of genes identified by the microarray analysis was validated by independent real-time PCR analysis. Among upregulated genes were Shrm, Tgfb2, Ube2l6, G1p2, Ccl7 while downregulated genes were Folr1, Tgfbr2, Csrp2, and Dlk1. These results support a versatile function of TFII-I proteins in vertebrate physiology and lead to an increased understanding of the BEN-dependent molecular events.

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.

Transcription factor TFII-I conducts a cytoplasmic orchestra

In response to extracellular ligands, surface receptor tyrosine kinases and G-protein-coupled receptors activate isoforms of phospholipase C (PLC) and initiate calcium signaling. PLC can activate expression of surface transient receptor potential channels (TRPC) such as TRPC3, which modulate calcium entry through the plasma membrane. A recent paper shows that competitive binding of cytoplasmic TFII-I, a transcription factor, to PLC-gamma results in inhibition of TRPC3-mediated agonist-induced Ca(2+) entry. These results establish a novel cytoplasmic function for TFII-I.

Action of TFII-I outside the nucleus as an inhibitor of agonist-induced calcium entry

TFII-I is a transcription factor and a target of phosphorylation by Bruton's tyrosine kinase. In humans, deletions spanning the TFII-I locus are associated with a cognitive defect, the Williams-Beuren cognitive profile. We report an unanticipated role of TFII-I outside the nucleus as a negative regulator of agonist-induced calcium entry (ACE) that suppresses surface accumulation of TRPC3 (transient receptor potential C3) channels. Inhibition of ACE by TFII-I requires phosphotyrosine residues that engage the SH2 (Src-homology 2) domains of phospholipase C-g (PLC-g) and an interrupted, pleckstrin homology (PH)-like domain that binds the split PH domain of PLC-g. Our observations suggest a model in which TFII-I suppresses ACE by competing with TRPC3 for binding to PLC-g.

Increased local gyrification mapped in Williams syndrome

Applying a recently developed method to analyze gyrification with excellent spatial resolution across thousands of points across the lateral and medial cortical surface, we mapped differences in cortical surface anatomy between subjects with Williams syndrome (WS; n=42) and an age-matched sample of healthy subjects (n=40). WS subjects showed increased gyrification bilaterally in occipital regions and over the cuneus. Differences were more pronounced in the left hemisphere than in the right, with additional regions of increased gyrification in WS in the left precuneus, posterior and anterior cingulate, paracentral and mesial frontal lobe. No cortical area was significantly more convoluted in healthy subjects relative to the WS subjects. On the lateral surfaces, the direction and pattern of gyrification asymmetries were similar in WS subjects and controls; posterior brain regions had greater gyrification in the left hemisphere, while anterior brain regions showed greater gyrification in the right hemisphere. On the medial surfaces, control subjects and WS individuals differed considerably with respect to the degree but also direction of gyrification asymmetry. Our findings confirm and extend previous studies measuring cortical complexity at the global whole-brain or hemispheric levels. The observed gyrification abnormalities in individuals with WS might be related to dysfunctions in neuronal circuits and consequently contribute to the distinct cognitive and behavioral profile accompanying the disorder.

Parieto-occipital grey matter abnormalities in children with Williams syndrome

Williams syndrome (WS) is a neurodevelopmental disorder resulting from a hemizygous deletion of chromosome 7q11.23. The phenotype of WS consists of typical dysmorphic features, supravalvular aortic stenosis, infantile hypercalcemia and growth retardation. While language and facial recognition seem to be relatively spared, visuospatial constructive disabilities are a hallmark of the neurobehavioral profile of WS. In order to search for actual structural abnormalities underlying this precisely defined neurodevelopmental disorder, we performed anatomical magnetic resonance imaging (MRI) in 9 WS children (11.6 +/- 3.1 years; age range: 5.5-15 years) and 11 normal age-matched control children (11.8 +/- 2.2 years; age range: 8-15 years) using voxel-based morphometry (VBM). VBM is a fully automated whole-brain technique that delivers a voxel-wise assessment of regional grey and white matter concentration. A significant decrease in grey matter concentration was detected in the left parieto-occipital region of WS children (P < 0.05 corrected height threshold). The location of this abnormality in WS children coincides with the location of the structural abnormality previously described using the same method in 13 WS adults. These parieto-occipital abnormalities are consistent with the cognitive profile of WS which includes severe visuospatial construction and numerical cognition deficits. The demonstration of identical structural abnormalities in both adults and children argues for their early origin. Additionally, our study provides support for the use of advanced structural imaging techniques in children, in order to improve our understanding of neurobehavioral phenotypes associated with well-defined genetic disorders.

Positive and negative regulation of the transforming growth factor beta/activin target gene goosecoid by the TFII-I family of transcription factors

Goosecoid (Gsc) is a homeodomain-containing transcription factor present in a wide variety of vertebrate species and known to regulate formation and patterning of embryos. Here we show that in embryonic carcinoma P19 cells, the transcription factor TFII-I forms a complex with Smad2 upon transforming growth factor beta (TGFbeta)/activin stimulation, is recruited to the distal element (DE) of the Gsc promoter, and activates Gsc transcription. Downregulation of endogenous TFII-I by small inhibitory RNA in P19 cells abolishes the TGFbeta-mediated induction of Gsc. Similarly, Xenopus embryos with endogenous TFII-I expression downregulated by injection of TFII-I-specific antisense oligonucleotides exhibit decreased Gsc expression. Unlike TFII-I, the related factor BEN (binding factor for early enhancer) is constitutively recruited to the distal element in the absence of TGFbeta/activin signaling and is replaced by the TFII-I/Smad2 complex upon TGFbeta/activin stimulation. Overexpression of BEN in P19 cells represses the TGFbeta-mediated transcriptional activation of Gsc. These results suggest a model in which TFII-I family proteins have opposing effects in the regulation of the Gsc gene in response to a TGFbeta/activin signal.

Vascular endothelial growth factor receptor-2: counter-regulation by the transcription factors, TFII-I and TFII-IRD1

The vascular endothelial growth factor receptor-2 (VEGFR-2/KDR/flk-1) functions as the primary mediator of vascular endothelial growth factor activation in endothelial cells. Regulation of VEGFR-2 expression appears critical in mitogenesis, differentiation, and angiogenesis. Transcriptional regulation of the VEGFR-2 is complex and may involve multiple putative upstream regulatory elements including E boxes. Transcript initiation is dependent on an initiator (Inr) element flanking the transcriptional start site. The transcription factor, TFII-I, enhances VEGFR-2 transcription in an Inr-dependent fashion. TFII-I is unusual both structurally and functionally. The TFII-I transcription factor family members contain multiple putative DNA binding domains. Functionally, TFII-I acts at both the basal, Inr element as well as at several distinct upstream regulatory sites. It has been postulated that the structure of TFII-I might allow simultaneous interaction with both basal and regulatory sites in a given promoter. As TFII-I is known to act at regulatory sites including E boxes as well as at the basal Inr element, we evaluated the possibility of Inr-independent TFII-I activation of the VEGFR-2 promoter. We found that an Inr-mutated VEGFR-2 reporter construct retains TFII-I-stimulated activity. We demonstrated that TFII-I binds to both the Inr and to three regulatory E boxes in the human VEGFR-2 promoter. In addition, reduction in TFII-I expression by siRNA results in decreased VEGFR-2 expression. We also describe counter-regulation of the VEGFR-2 promoter by TFII-IRD1. We found that TFII-I is capable of acting at both basal and regulatory sites in one promoter and that the human VEGFR-2 promoter is functionally counter-regulated by TFII-I and TFII-IRD1.

Frizzled 9 knock-out mice have abnormal B-cell development

The binding of frizzled (Fzd) receptors by their Wnt ligands results in the inhibition of beta-catenin degradation and subsequent transcription of beta-catenin/LEF-inducible genes. The beta-catenin pathway is known to be involved in development, tumorigenesis, and stem cell self-renewal. In humans, the FZD9 gene lies in the region of chromosome 7q11.23 deleted in the neurodevelopmental disorder, Williams-Beuren syndrome (WBS). Fzd9-/- mice show no obvious features of WBS, but reveal a role for Fzd9 in lymphoid development and maturation. Fzd9-/- mice show pronounced splenomegaly, thymic atrophy, and lymphadenopathy with age, with accumulation of plasma cells in lymph nodes. There is a depletion of developing B cells in the bone marrow (BM), particularly in the pre-B stage where immunoglobulin heavy chains are expressed and the cells are undergoing clonal expansion prior to light chain rearrangement. The pre-B defect is partially intrinsic to the hematopoietic system; as in competitive BM reconstitution studies, Fzd9-/- -derived BM exhibits defective B-cell development when implanted into a wild-type host. Mature B cells are present in normal numbers in lymph node and spleen. These findings suggest a role for Fzd9 signaling in lymphoid development, particularly at points where B cells undergo self-renewal prior to further differentiation.

Neural Basis of Genetically Determined Visuospatial Construction Deficit in Williams Syndrome

A unique opportunity to understand genetic determinants of cognition is offered by Williams syndrome (WS), a well-characterized hemideletion on chromosome 7q11.23 that causes extreme, specific weakness in visuospatial construction (the ability to visualize an object as a set of parts or construct a replica). Using multimodal neuroimaging, we identified a neural mechanism underlying the WS visuoconstructive deficit. Hierarchical assessment of visual processing with fMRI showed isolated hypoactivation in WS in the parietal portion of the dorsal stream. In the immediately adjacent parietooccipital/intraparietal sulcus, structural neuroimaging showed a gray matter volume reduction in participants with WS. Path analysis demonstrated that the functional abnormalities could be attributed to impaired input from this structurally altered region. Our observations confirm a longstanding hypothesis about dorsal stream dysfunction in WS, demonstrate effects of a localized abnormality on visual information processing in humans, and define a systems-level phenotype for mapping genetic determinants of visuoconstructive function.

Multisystem study of 20 older adults with Williams syndrome

To address the natural history of Williams syndrome (WS), we performed multisystem assessments on 20 adults with WS over 30 years of age and documented a high frequency of problems in multiple organ systems. The most striking and consistent findings were: abnormal body habitus; mild-moderate high frequency sensorineural hearing loss; cardiovascular disease and hypertension; gastrointestinal symptoms including diverticular disease; diabetes and abnormal glucose tolerance on standard oral glucose tolerance testing; subclinical hypothyroidism; decreased bone mineral density on DEXA scanning; and a high frequency of psychiatric symptoms, most notably anxiety, often requiring multimodal therapy. Review of brain MRI scans did not demonstrate consistent pathology. The adults in our cohort were not living independently and the vast majority were not competitively employed. Our preliminary findings raise concern about the occurrence of mild accelerated aging, which may additionally complicate the long-term natural history of older adults with WS. We provide monitoring guidelines to assist in the comprehensive care of adults with WS.