Hemizygous deletion of the syntaxin 1A gene in individuals with Williams syndrome

Functional regulation of syntaxin-1: An underlying mechanism mediating exocytosis in neuroendocrine cells

The fusion of the secretory vesicle with the plasma membrane requires the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein complexes formed by synaptobrevin, syntaxin-1, and SNAP-25. Within the pathway leading to exocytosis, the transitions between the "open" and "closed" conformations of syntaxin-1 function as a switch for the fusion of vesicles with the plasma membranes; rapid assembly and disassembly of syntaxin-1 clusters on the plasma membrane provide docking and fusion sites for secretory vesicles in neuroendocrine cells; and the fully zippered trans-SNARE complex, which requires the orderly, rapid and accurate binding of syntaxin-1 to other SNARE proteins, play key roles in triggering fusion. All of these reactions that affect exocytosis under physiological conditions are tightly regulated by multiple factors. Here, we review the current evidence for the involvement of syntaxin-1 in the mechanism of neuroendocrine cell exocytosis, discuss the roles of multiple factors such as proteins, lipids, protein kinases, drugs, and toxins in SNARE complex-mediated membrane fusion, and present an overview of syntaxin-1 mutation-associated diseases with a view to developing novel mechanistic therapeutic targets for the treatment of neuroendocrine disorders.

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.

Oxytocin and Oxytocin Receptor Gene Regulation in Williams Syndrome: A Systematic Review

Williams Syndrome (WS) is a rare genetic multisystem disorder that occurs because of a deletion of approximately 25 genes in the 7q11.23 chromosome region. This causes dysmorphic facial appearances, multiple congenital cardiovascular defects, delayed motor skills, and abnormalities in connective tissues and the endocrine system. The patients are mostly diagnosed with mild to moderate mental retardation, however, they have a hyper sociable, socially dis-inhibited, and outgoing personality, empathetic behavior, and are highly talkative. Oxytocin (OT), a neuropeptide synthesized at the hypothalamus, plays an important role in cognition and behavior, and is thought to be affecting WS patients' attitudes at its different amounts. Oxytocin receptor gene (OXTR), on chromosome 3p25.3, is considered regulating oxytocin receptors, via which OT exerts its effect. WS is a crucial disorder to understand gene, hormone, brain, and behavior associations in terms of sociality and neuropsychiatric conditions. Alterations to the WS gene region offer an opportunity to deepen our understandings of autism spectrum disorder, schizophrenia, anxiety, or depression. We aim to systematically present the data available of OT/OXTR regulation and expression, and the evidence for whether these mechanisms are dysregulated in WS. These results are important, as they predict strong epigenetic control over social behavior by methylation, single nucleotide polymorphisms, and other alterations. The comparison and collaboration of these studies may help to establish a better treatment or management approach for patients with WS if backed up with future research.

Disorders of synaptic vesicle fusion machinery

The revolution in genetic technology has ushered in a new age for our understanding of the underlying causes of neurodevelopmental, neuromuscular and neurodegenerative disorders, revealing that the presynaptic machinery governing synaptic vesicle fusion is compromised in many of these neurological disorders. This builds upon decades of research showing that disturbance to neurotransmitter release via toxins can cause acute neurological dysfunction. In this review, we focus on disorders of synaptic vesicle fusion caused either by toxic insult to the presynapse or alterations to genes encoding the key proteins that control and regulate fusion: the SNARE proteins (synaptobrevin, syntaxin-1 and SNAP-25), Munc18, Munc13, synaptotagmin, complexin, CSPα, α-synuclein, PRRT2 and tomosyn. We discuss the roles of these proteins and the cellular and molecular mechanisms underpinning neurological deficits in these disorders.

SNAREs and developmental disorders

Members of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family mediate membrane fusion processes associated with vesicular trafficking and autophagy. SNAREs mediate core membrane fusion processes essential for all cells, but some SNAREs serve cell/tissue type-specific exocytic/endocytic functions, and are therefore critical for various aspects of embryonic development. Mutations or variants of their encoding genes could give rise to developmental disorders, such as those affecting the nervous system and immune system in humans. Mutations to components in the canonical synaptic vesicle fusion SNARE complex (VAMP2, STX1A/B, and SNAP25) and a key regulator of SNARE complex formation MUNC18-1, produce variant phenotypes of autism, intellectual disability, movement disorders, and epilepsy. STX11 and MUNC18-2 mutations underlie 2 subtypes of familial hemophagocytic lymphohistiocytosis. STX3 mutations contribute to variant microvillus inclusion disease. Chromosomal microdeletions involving STX16 play a role in pseudohypoparathyroidism type IB associated with abnormal imprinting of the GNAS complex locus. In this short review, I discuss these and other SNARE gene mutations and variants that are known to be associated with a variety developmental disorders, with a focus on their underlying cellular and molecular pathological basis deciphered through disease modeling. Possible pathogenic potentials of other SNAREs whose variants could be disease predisposing are also speculated upon.

Neuronal SNARE complex: A protein folding system with intricate protein-protein interactions, and its common neuropathological hallmark, SNAP25

SNARE (Soluble NSF(N-ethylmaleimide-sensitive factor) Attachment Receptor) complex is a trimeric supramolecular organization of SNAP25, syntaxin, and VAMP which mediates fusion of synaptic vesicles with the presynaptic plasma membrane. The functioning of this entire protein assembly is dependent on its tetrahelical coiled coil structure alongside its interaction with a large spectrum of regulatory proteins like synaptotagmin, complexin, intersectin, etc. Defects arising in SNARE complex assembly due to mutations or faulty post-translational modifications are associated to severe synaptopathies like Schizophrenia and also proteopathies like Alzheimer's disease. The review primarily focuses on SNAP25, which is the prime contributor in the complex assembly. It is conceptualized that the network of protein interactions of this helical protein assists as a chaperoning system for attaining functional structure. Additionally, the innate disordered nature of SNAP25 and its amyloidogenic propensities have been highlighted employing computational methods. The intrinsic nature of SNAP25 is anticipated to form higher-order aggregates due to its cysteine rich domain, which is also a target for several post-translational modifications. Furthermore, the aberrations in the structure and expression profile of the protein display common patterns in the pathogenesis of a diverse synaptopathies and proteopathies. This work of SNARE literature aims to provide a new comprehensive outlook and research directions towards SNARE complex and presents SNAP25 as a common neuropathological hallmark which can be a diagnostic or therapeutic target.

Impaired glucose metabolism in subjects with the Williams-Beuren syndrome: A five-year follow-up cohort study

Objective

The Williams-Beuren syndrome (WS) is associated with impaired glucose metabolism (IGM) early in adulthood. However, the pathophysiology of IGM remains poorly defined, due to the lack of longitudinal studies investigating the contribution of β-cell dysfunction and impaired insulin sensitivity. This study aimed at assessing incidence of IGM and the underlying mechanisms in WS adults.

Methods

This observational, longitudinal (5-year), cohort study enrolled thirty-one consecutive WS subjects attending a tertiary referral center. An oral glucose tolerance test (OGTT) was performed yearly and used to classify patients as normal or IGM, including impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) and diabetes mellitus (DM), and to calculate surrogate measures of insulin secretion and/or sensitivity.

Results

IGM patients were 18 (58.1%, three DM) at baseline and 19 (61.3%, five DM) at end-of-follow-up. However, 13 individuals changed category of glucose homeostasis in both directions during follow-up (8 progressors, 5 regressors) and 18 did not (8 non-progressors, 10 non-regressors). New cases of IGM and DM were 11.1 and 2.53 per 100 persons-year, respectively, and were treated non-pharmacologically. In the whole cohort and, to a higher extent, in progressors, indices of early-phase insulin secretion and insulin sensitivity decreased significantly from baseline to end-of-follow-up, with concurrent reduction of the oral disposition index and insulin secretion-sensitivity index-2 (ISSI-2), compensating insulin secretion for the level of insulin resistance. No baseline measure independently predicted progression, which correlated with change from baseline in ISSI-2. Compared with patients with normal glucose homeostasis, IGT subjects had impaired insulin sensitivity, whereas insulin secretion was reduced only in those with IFG+IGT or DM.

Conclusions

IGM incidence is high in young adults with WS, suggesting the need of early screening and timed intervention. As in classical type 2 diabetes, impaired insulin sensitivity and β-cell dysfunction contribute, in this sequence, to progression to IGM and DM.

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

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

Imaging analysis reveals mechanistic differences between first- and second-phase insulin exocytosis

The mechanism of glucose-induced biphasic insulin release is unknown. We used total internal reflection fluorescence (TIRF) imaging analysis to reveal the process of first- and second-phase insulin exocytosis in pancreatic β cells. This analysis showed that previously docked insulin granules fused at the site of syntaxin (Synt)1A clusters during the first phase; however, the newcomers fused during the second phase external to the Synt1A clusters. To reveal the function of Synt1A in phasic insulin exocytosis, we generated Synt1A-knockout (Synt1A^−/−) mice. Synt1A^−/− β cells showed fewer previously docked granules with no fusion during the first phase; second-phase fusion from newcomers was preserved. Rescue experiments restoring Synt1A expression demonstrated restoration of granule docking status and fusion events. Inhibition of other syntaxins, Synt3 and Synt4, did not affect second-phase insulin exocytosis. We conclude that the first phase is Synt1A dependent but the second phase is not. This indicates that the two phases of insulin exocytosis differ spatially and mechanistically.

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.

Transgenic mouse overexpressing syntaxin-1A as a diabetes model

Soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor (SNARE) protein syntaxin-1A (STX-1A) plays a role not only in exocytosis, but also binds and regulates Ca(2+) and K(+) (voltage-gated K(+) and ATP-sensitive K(+) channels) to influence the sequence of events leading to secretion. Islet levels of STX-1A and cognate SNARE proteins are reduced in type 2 diabetic rodents, suggesting their role in dysregulated insulin secretion contributing to the abnormal glucose homeostasis. We investigated the specific role of STX-1A in pancreatic beta-cells by generating transgenic mice, which express a moderately increased level ( approximately 30% higher) of STX-1A in pancreatic islets (hereafter called STX-1A mice). The STX-1A mice displayed fasting hyperglycemia and a more sustained elevation of plasma glucose levels after an intraperitoneal glucose tolerance test, with correspondingly reduced plasma insulin levels. Surprisingly, beta-cells from the STX-1A male mice also exhibited abnormal insulin tolerance. To unequivocally determine the beta-cell secretory defects, we used single-cell analyses of exocytosis by patch clamp membrane capacitance measurements and ion channel recordings. Depolarization-evoked membrane capacitance increases were reduced in the STX-1A mouse islet beta-cells. The STX-1A mouse also exhibited reduced currents through the Ca(2+) channels but little change in the voltage-gated K(+) channel or ATP-sensitive K(+) channel. These results suggest that fluctuation of islet STX-1A levels in diabetes could influence the pathological and differential regulation of beta-cell ion channels and the exocytotic machinery, collectively contributing to the impaired insulin secretion.

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

The gene for TFII-I, a widely expressed transcription factor, has been localized to an interval of human chromosome 7q11.23 that is commonly deleted in Williams syndrome (WS). The clinical phenotype of WS includes elfin facies, infantile hypercalcemia, supravalvular aortic stenosis, hyperacusis and mental retardation. The WS cognitive profile (WSCP) is notable for the differential impairment of visual-spatial abilities with relative sparing of verbal-linguistic function. Fine mapping of individuals with WS has revealed a close association between deletion of TFII-I and the WSCP. To determine the plausibility of the hypothesis that hemizygous deletion of TFII-I contributes to the WSCP, we have examined the anatomic distribution of TFII-I RNA and protein isoforms in brains from adult and embryonic mice. Our studies show that early in development, TFII-I expression is widespread and nearly uniform throughout the brain. In adult brain, TFII-I protein is present exclusively in neurons. Highest levels of expression are observed in cerebellar Purkinje cells and in hippocampal interneurons. TFII-I immunoreactivity is distinct from that of the related protein, TFII-IRD1, which is also localized to the region of human chromosome 7 deleted in WS. The expression pattern of TFII-I in mouse brain parallels regions in human brain which have been shown to be anatomically and functionally altered in humans with WS. These observations are consistent with the hypothesis that deletion of the gene for TFII-I contributes to the cognitive impairments observed in WS.

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

Most individuals with Williams syndrome (WS) have a 1.6 Mb deletion in chromosome 7q11.23 that encompasses the elastin (ELN) gene, while most families with autosomal dominant supravalvar aortic stenosis (SVAS) have point mutations in ELN. The overlap of the clinical phenotypes of the two conditions (cardiovascular disease and connective tissue abnormalities such as hernias) is due to the effect of haploinsufficiency of ELN. SVAS families often have affected individuals with some WS facial features, most commonly in infancy, suggesting that ELN plays a role in WS facial gestalt as well. To find other genes contributing to the WS phenotype, we studied five families with SVAS who have small deletions in the WS region. None of the families had mental retardation, but affected family members had the Williams Syndrome Cognitive Profile (WSCP). All families shared a deletion of LIMK1, which encodes a protein strongly expressed in the brain, supporting the hypothesis that LIMK1 hemizygosity contributes to impairment in visuospatial constructive cognition. While the deletions from the families nearly spanned the WS region, none had a deletion of FKBP6 or GTF2I, suggesting that the mental retardation seen in WS is associated with deletion of either the centromeric and/or telomeric portions of the region. Comparison of these five families with reports of other individuals with partial deletions of the WS region most strongly implicates GTF2I in the mental retardation of WS.

Expression of syntaxin 1C, an alternative splice variant of HPC-1/syntaxin 1A, is enhanced by phorbol-ester stimulation in astroglioma: participation of the PKC signaling pathway

Syntaxin 1C is an alternative splice variant of HPC-1/syntaxin 1A; the latter participates in neurotransmitter release and is assigned to the gene domain responsible for Williams' syndrome (WS). It is expressed in the soluble fraction extracted from human astroglioma cell lines T98G and U87MG. Quantitative immunoblot and indirect immunofluorescence analyses revealed that the expression of syntaxin 1C was upregulated by phorbol 12-myristate 13-acetate (PMA), but not by forskolin. A protein kinase C (PKC) inhibitor suppressed this enhancement. These results suggest that syntaxin 1C expression is regulated via the PKC signal pathway. This is the first report of a signal transduction system that directly affects the expression of syntaxin protein.

Morphology and morphometry of the corpus callosum in Williams syndrome: a T1-weighted MRI study

Williams syndrome (WS) is characterised by a defined genetic aetiology and a specific cognitive profile. It provides an opportunity to examine associations between neuroanatomy, behaviour, and genetics. High-resolution T1-weighted MRI of the brain of 12 patients with WS and 12 normal control subjects were used to estimate the shape and volume of the corpus callosum (CC), as well as the voxel intensity values as a measure its water content. The CC of patients with WS was more convex than that of normal control subjects and overall smaller in volume, particularly in the splenium and in the caudal part of the callosal body. In addition, there were higher ratio values of voxel intensity (i.e. less water content) in the mid-section of the body and the caudal part of the body of the CC. These combined features indicate an aberrant development of the CC in patients with WS and document some of the anatomical abnormalities that may underlie some of the cognitive impairments observed in subjects with WS.

Refinement of the genomic structure of STX1A and mutation analysis in nondeletion Williams syndrome patients

Williams syndrome (WS) is a contiguous gene deletion disorder in which the commonly deleted region contains at least 17 genes. One of these genes, Syntaxin 1A (STX1A), codes for a protein that is highly expressed in the nervous system and is essential for the docking of synaptic vesicles with the presynaptic plasma membrane. In this study, we refine the complete genomic structure of the human STX1A gene by direct sequencing and primer walking of bacterial artificial chromosome (BAC) clones and show that STX1A contains at least 10 exons and 9 introns. The length of exons range from 27 bp to 138 bp and all splice sites conform to the GT-AG rule. Investigation of the STX1A gene sequence in five WS patients without detectable deletions did not identify any point mutations. Although the regulatory elements that control STX1A transcription were not examined, these results do not support a role for STX1A in the WS phenotype.

Williams syndrome and related disorders

Three clinical conditions displaying phenotypic overlap have been linked to mutation or deletion of the elastin gene at 7q11.23. Supravalvar aortic stenosis, an autosomal dominant disorder characterized by elastin arteriopathy, is caused by mutation or intragenic deletions of ELN resulting in loss of function. Autosomal dominant cutis laxa, a primarily cutaneous condition, is the result of frameshift mutations at ELN that cause a dominant-negative effect on elastic fiber structure. Williams syndrome, a neurodevelopmental disorder is due to a 1.5 Mb deletion that includes ELN and at least 15 contiguous genes. The disorder is characterized by dysmorphic facies, mental retardation or learning difficulties, elastin arteriopathy, a unique cognitive profile of relative strength in auditory rote memory and language and extreme weakness in visuospatial constructive cognition, and a typical personality that includes overfriendliness, anxiety, and attention problems. The understanding of these disorders has progressed from phenotypic description to identification of causative mutations and insight into pathogenetic mechanisms for some aspects of the phenotype.

Generation and comparative analysis of approximately 3.3 Mb of mouse genomic sequence orthologous to the region of human chromosome 7q11.23 implicated in Williams syndrome

Williams syndrome is a complex developmental disorder that results from the heterozygous deletion of a approximately 1.6-Mb segment of human chromosome 7q11.23. These deletions are mediated by large (approximately 300 kb) duplicated blocks of DNA of near-identical sequence. Previously, we showed that the orthologous region of the mouse genome is devoid of such duplicated segments. Here, we extend our studies to include the generation of approximately 3.3 Mb of genomic sequence from the mouse Williams syndrome region, of which just over 1.4 Mb is finished to high accuracy. Comparative analyses of the mouse and human sequences within and immediately flanking the interval commonly deleted in Williams syndrome have facilitated the identification of nine previously unreported genes, provided detailed sequence-based information regarding 30 genes residing in the region, and revealed a number of potentially interesting conserved noncoding sequences. Finally, to facilitate comparative sequence analysis, we implemented several enhancements to the program, including the addition of links from annotated features within a generated percent-identity plot to specific records in public databases. Taken together, the results reported here provide an important comparative sequence resource that should catalyze additional studies of Williams syndrome, including those that aim to characterize genes within the commonly deleted interval and to develop mouse models of the disorder.

Bends in human mitotic metaphase chromosomes revisited: 15q11-13 is the most frequent non-random autosomal bend in blood cultures

We have investigated the preferential bending of some chromosome sites in blood cultures from normal and chromosomally abnormal subjects. A total of 2,262 centromeric and 2,718 non-centromeric bends were recorded, and 69 non-centromeric sites were found not to bend at random. 15q11-13 bending was found to be the most frequent non-random autosomal bend. Bends on chromosomes may be remnants of a folded chromosome state in the nucleus, and may facilitate the preferential involvement of some chromosomal bands in structural reorganizations such as the isoacentric fragments, or contribute to the high frequency of interstitial deletions and isodicentric inversion duplications involving the 15q11-13 region.

V. Multi-level analysis of cortical neuroanatomy in Williams syndrome

The purpose of a neuroanatomical analysis of Williams Syndrome (WMS) brains is to help bridge the knowledge of the genetics of this disorder with the knowledge on behavior. Here, we outline findings of cortical neuroanatomy at multiple levels. We describe the gross anatomy with respect to brain shape, cortical folding, and asymmetry. This, as with most neuroanatomical information available in the literature on anatomical-functional correlations, links up best to the behavioral profile. Then, we describe the cytoarchitectonic appearance of the cortex. Further, we report on some histometric results. Finally, we present findings of immunocytochemistry that attempt to link up to the genomic deletion. The gross anatomical findings consist mainly of a small brain that shows curtailment in the posterior-parietal and occipital regions. There is also subtle dysmorphism of cortical folding. A consistent finding is a short central sulcus that does not become opercularized in the interhemispheric fissure, bringing attention to a possible developmental anomaly affecting the dorsal half of the hemispheres. There is also lack of asymmetry in the planum temporale. The cortical cytoarchitecture is relatively normal, with all sampled areas showing features typical of the region from which they are taken. Measurements in area 17 show increased cell size and decreased cell-packing density, which address the issue of possible abnormal connectivity. Immunostaining shows absence of elastin but normal staining for Lim-1 kinase, both of which are products of genes that are part of the deletion. Finally, one serially sectioned brain shows a fair amount of acquired pathology of microvascular origin related most likely to underlying hypertension and heart disease.

Fine-scale comparative mapping of the human 7q11.23 region and the orthologous region on mouse chromosome 5G: the low-copy repeats that flank the Williams-Beuren syndrome deletion arose at breakpoint sites of an evolutionary inversion(s)

Williams-Beuren syndrome (WBS) is a developmental disorder caused by haploinsufficiency for genes deleted in chromosome band 7q11.23. A common deletion including at least 16-17 genes has been defined in the great majority of patients. We have completed a physical and transcription map of the WBS region based on analysis of high-throughput genome sequence data and assembly of a BAC/PAC/YAC contig, including the characterization of large blocks of gene-containing low-copy-number repeat elements that flank the commonly deleted interval. The WBS deletions arise as a consequence of unequal crossing over between these highly homologous sequences, which confer susceptibility to local chromosome rearrangements. We have also completed a clone contig, genetic, and long-range restriction map of the mouse homologous region, including the orthologues of all identified genes in the human map. The order of the intradeletion genes appears to be conserved in mouse, and no low-copy-number repeats are found in the region. However, the deletion region is inverted relative to the human map, exactly at the flanking regions. Thus, we have identified an evolutionary inversion with chromosomal breakpoints at the sites where the human 7q11.23 low-copy-number repeats are located. Additional comparative mapping suggests a model for human chromosome 7 evolution due to serial inversions leading to genomic duplications. This high-resolution mouse map provides the framework required for the generation of mouse models for WBS mimicking the human molecular defect.

Characterization and gene structure of a novel retinoblastoma-protein-associated protein similar to the transcription regulator TFII-I

Retinoblastoma protein (Rb) is an important regulator of vertebrate cell cycle and development. It functions through a direct interaction with protein factors involved in cell cycle progression and differentiation. In the present study we characterized a novel Rb-associated protein, Cream1, which bound to Rb specifically through a C-terminal region. Cream1 contained 959 amino acid residues and migrated as a protein of approx. 120 kDa on SDS/PAGE. It was a widely expressed nuclear protein with a nuclear localization signal resembling that of the large T antigen of simian virus 40. Its primary sequence was characteristic of five direct repeats that were similar to, but distinct from, those of TFII-I, a multifunctional transcription regulator. Three additional regions were also highly conserved in both proteins. Cream1 exhibited an activation activity that was attributed to its N-terminal portion when assayed in yeast. Its relationship with the muscle-enhancer-binding protein MusTRD1 further suggests a role in regulating gene expression. The structural gene, CREAM1, contained 27 exons and spanned more than 150 kb. It was located at human chromosome 7q11.23 in a region deleted for Williams' syndrome, a neurodevelopmental disease with multisystem abnormalities, implying its involvement in certain disorders. Taken together, our results suggest that Cream1 might serve as a positive transcription regulator under the control of Rb.

Elastin region deletions in Williams syndrome

Williams syndrome (WS) is considered a contiguous gene syndrome, with most patients having a 1.5-Mb deletion of chromosome 7q11.23 containing the elastin gene and flanking genes. Studies of the frequency, extent, and origin of these deletions are ongoing in many labs to discover ultimately the molecular and pathogenetic basis for WS. An analysis of 9 sporadic WS families with typical phenotypes was performed by genotyping polymorphisms in the region. This study revealed deletions in all 9 patients, with one showing a novel deletion extending much further centromeric than any other WS deletions yet reported.

A physical map, including a BAC/PAC clone contig, of the Williams-Beuren syndrome--deletion region at 7q11.23

Williams-Beuren syndrome (WBS) is a developmental disorder caused by haploinsufficiency for genes in a 2-cM region of chromosome band 7q11.23. With the exception of vascular stenoses due to deletion of the elastin gene, the various features of WBS have not yet been attributed to specific genes. Although >/=16 genes have been identified within the WBS deletion, completion of a physical map of the region has been difficult because of the large duplicated regions flanking the deletion. We present a physical map of the WBS deletion and flanking regions, based on assembly of a bacterial artificial chromosome/P1-derived artificial chromosome contig, analysis of high-throughput genome-sequence data, and long-range restriction mapping of genomic and cloned DNA by pulsed-field gel electrophoresis. Our map encompasses 3 Mb, including 1.6 Mb within the deletion. Two large duplicons, flanking the deletion, of >/=320 kb contain unique sequence elements from the internal border regions of the deletion, such as sequences from GTF2I (telomeric) and FKBP6 (centromeric). A third copy of this duplicon exists in inverted orientation distal to the telomeric flanking one. These duplicons show stronger sequence conservation with regard to each other than to the presumptive ancestral loci within the common deletion region. Sequence elements originating from beyond 7q11.23 are also present in these duplicons. Although the duplicons are not present in mice, the order of the single-copy genes in the conserved syntenic region of mouse chromosome 5 is inverted relative to the human map. A model is presented for a mechanism of WBS-deletion formation, based on the orientation of duplicons' components relative to each other and to the ancestral elements within the deletion region.

Elastin gene deletions in Williams syndrome patients result in altered deposition of elastic fibers in skin and a subclinical dermal phenotype

Williams syndrome (WS) is a complex developmental disorder with multisystem involvement known to be the result of a microdeletion in the q11.23 region of chromosome 7. This deletion involves several genes, including the elastin gene. Although elastic fibers are important constituents of skin, little is known about the skin phenotype in WS patients. We have therefore studied the skin of four WS patients in which we've shown the deletion of one copy of the elastin gene. Physical examination and indirect immunofluorescent microscopy of elastin did not detect any major phenotypic or morphologic changes in the skin. We were able, however, to show subtle textural changes in skin and, by electron microscopy, that the amorphous component of elastic fibers in WS patients was consistently reduced when compared to normal controls. These findings indicate that deletion of one copy of the elastin gene results in reduced deposition of elastin in dermal elastic fibers, an altered elastic fiber ultrastructure, and a subclinical dermal phenotype in the children and young adult patients analyzed in this study.

Expression analysis and protein localization of the human HPC-1/syntaxin 1A, a gene deleted in Williams syndrome

The HPC-1/syntaxin 1A (STX1A) gene maps to the Williams syndrome (WS) commonly deleted region on chromosome 7q11.23 and encodes a protein implicated in the docking of synaptic vesicles with the presynaptic plasma membrane. To assess the potential role of STX1A in the WS phenotype, we carried out expression studies at the RNA and protein levels, in fetal and adult human tissues. RNA in situ hybridization on human embryo sections showed strong STX1A expression in spinal cord and ganglia. However, in adulthood, this gene was preferentially expressed in brain, as shown by Northern blot and RT-PCR experiments. Marked expression levels were observed in cerebellum and cerebral cortex. The STX1A protein was prevalently distributed in the molecular layer of the cerebellar cortex. A qualitative and quantitative analysis using a specific anti-STX1A antibody did not disclose any significant difference among frontal, temporal, and occipital poles of the human adult cortex in the two hemispheres. This is the first study focused on STX1A expression in humans. Our results indicate that this gene is strongly expressed in cerebral areas involved in cognitive process, supporting a likely role in the neurological symptoms of WS.

A complete physical contig and partial transcript map of the Williams syndrome critical region

Williams syndrome (WS) is a contiguous gene syndrome caused by hemizygosity for a chromosomal deletion at 7q11.23. The range of phenotypes includes mental retardation, dysmorphic facies, heart abnormalities, short stature, a specific cognitive profile, hyperacusis, and infantile hypercalcaemia. To identify all the deleted genes, we have constructed a detailed physical map and complete BAC/PAC contig of the critical region, extending a distance of approximately 2 Mb and delimited by the nondeleted markers D7S1816 and D7S489A. Somatic cell hybrids of WS patients were made and used to define the centromeric and telomeric deletion breakpoints, enabling the size of the WS deletion to be defined as approximately 1.4 Mb. Genes previously mapped to the region have been located on the contig, and we have isolated eight transcripts, two of which have been characterized as the genes CPETR1 and CPETR2. This contig and expressed sequence map will form the basis for the construction of a complete transcription map of the deleted region and will enable genotype-phenotype correlations to be attempted to identify the individual components of WS.

Comparative mapping of the region of human chromosome 7 deleted in williams syndrome

Williams syndrome (WS) is a complex developmental disorder resulting from the deletion of a large (approximately 1.5-2 Mb) segment of human chromosome 7q11.23. Physical mapping studies have revealed that this deleted region, which contains a number of known genes, is flanked by several large, nearly identical blocks of DNA. The presence of such highly related DNA segments in close physical proximity to one another has hampered efforts to elucidate the precise long-range organization of this segment of chromosome 7. To gain insight about the structure and evolutionary origins of this important and complex genomic region, we have constructed a fully contiguous bacterial artificial chromosome (BAC) and P1-derived artificial chromosome (PAC) contig map encompassing the corresponding region on mouse chromosome 5. In contrast to the difficulties encountered in constructing a clone-based physical map of the human WS region, the BAC/PAC-based map of the mouse WS region was straightforward to construct, with no evidence of large duplicated segments, such as those encountered in the human WS region. To confirm this difference, representative human and mouse BACs were used as probes for performing fluorescence in situ hybridization (FISH) to metaphase and interphase chromosomes. Human BACs derived from the nonunique portion of the WS region hybridized to multiple, closely spaced regions on human chromosome 7q11.23. In contrast, corresponding mouse BACs hybridized to a single site on mouse chromosome 5. Furthermore, FISH analysis revealed the presence of duplicated segments within the WS region of various nonhuman primates (chimpanzee, gorilla, orangutan, and gibbon). Hybridization was also noted at the genomic locations corresponding to human chromosome 7p22 and 7q22 in human, chimpanzee, and gorilla, but not in the other animal species examined. Together, these results indicate that the WS region is associated with large, duplicated blocks of DNA on human chromosome 7q11.23 as well as the corresponding genomic regions of other nonhuman primates. However, such duplications are not present in the mouse.

Bridging cognition, the brain and molecular genetics: evidence from Williams syndrome

Williams syndrome (WMS) is a rare sporadic disorder that yields a distinctive profile of medical, cognitive, neurophysiological, neuroanatomical and genetic characteristics. The cognitive hallmark of WMS is a dissociation between language and face processing (relative strengths) and spatial cognition (profound impairment). Individuals with WMS also tend to be overly social, behavior that is opposite to that seen in autism. A genetic hallmark of WMS is a deletion on chromosome band 7q11.23. Williams syndrome is also associated with specific neuromorphological and neurophysiological profiles: proportional sparing of frontal, limbic and neocerebellar structures is seen using MRI; and abnormal functional organization of the neural systems that underlie both language and face processing is revealed through studies using event-related potentials. The non-uniformity in the cognitive, neuromorphological and neurophysiological domains of WMS make it a compelling model for elucidating the relationships between cognition, the brain and, ultimately, the genes.

Identification of a putative transcription factor gene (WBSCR11) that is commonly deleted in Williams-Beuren syndrome

Williams-Beuren syndrome (WBS) is a complex developmental disorder involving the hemizygous deletion of genes on chromosome 7q11.23. The cardiovascular aspects of the disorder are known to be caused by haploinsufficiency for ELN, but the genes contributing to the other features of WBS are still undetermined. Fifteen genes have been shown to reside within the WBS deletion, and here we report the identification and cloning of an additional gene that is commonly deleted. WBSCR11, which was identified through genomic DNA sequence analysis and cDNA library screening, was positioned toward the telomeric end of the WBS deletion. The gene is expressed in all adult tissues analyzed, including many regions of the brain. The predicted protein displays homology to another gene from the WBS deletion, GTF2I, which is known to be a transcription factor. We postulate that WBSCR11 is also a transcription factor and may contribute to the spectrum of developmental symptoms found in WBS.

Characterization and expression pattern of the frizzled gene Fzd9, the mouse homolog of FZD9 which is deleted in Williams-Beuren syndrome

The frizzled gene family is conserved from insects to mammals and codes for putative Wnt receptors that share a cysteine-rich extracellular domain and seven transmembrane domains. We previously identified a novel frizzled gene, FZD3, now renamed FZD9, in the Williams-Beuren syndrome (WBS) deletion region at chromosomal band 7q11.23 and showed that its product can interact with the Drosophila wingless protein. Here, we report the characterization of the mouse homolog Fzd9. The Fzd9 gene produces a 2.4-kb transcript encoding a 592-amino-acid protein with 95% identity to the human FZD9. Fzd9 was mapped to the conserved syntenic region on distal mouse chromosome 5. By RNA in situ hybridization studies of whole-mount embryos and sections we delineated the temporal and spatial expression patterns in the neural tube, trunk skeletal muscle precursors (myotomes), limb skeletal anlagen, craniofacial regions, and nephric ducts. In adult mouse tissue, the Fzd9 transcript is abundantly present in heart, brain, testis, and skeletal muscle. In testis, Fzd9 is expressed in all spermatogenic cell types. Immunohistochemical studies of cells transfected with a Fzd9 expression construct confirm that Fzd9 is a membrane protein. These results suggest potential Wnt ligands of Fzd9, a role of Fzd9 in skeletal muscle specification, and contributions of FZD9 to the WBS phenotype.

cDNA characterization and chromosomal mapping of human golgi SNARE GS27 and GS28 to chromosome 17

Transport of proteins along the exocytotic pathway is primarily achieved by vesicular intermediates. Two proteins, Golgi SNAREs of 27 kDa, GS27, and of 28 kDa, GS28 (HGMW-approved nomenclature GOSR2 and GOSR1, respectively), are important trafficking membrane proteins between the endoplasmic reticulum and the Golgi and between Golgi subcompartments. Here, we present the human GS27 and GS28 cDNA sequences. They encode predicted proteins of 212 and 250 amino acids, respectively. Chromosomal mapping analyses reveal that human GS27 is located on chromosome 17q21 and GS28 on approximately 17q11. The chromosomal location of GS27 near a locus implicated in familial essential hypertension and its known function in trafficking indicate that it is a potential candidate gene for this disease.

Williams-Beuren syndrome: an update and review for the primary physician

Williams-Beuren syndrome is an autosomal dominant disorder resulting from a submicroscopic deletion of contiguous genes on the long arm of chromosome 7. It consists of a variety of hallmark physical features, which include distinctive facial characteristics, cardiac anomalies (of which the most common is supravalvular aortic stenosis), and occasional idiopathic hypercalcemia. The condition also includes a unique cognitive profile, with relative sparing of language and facial recognition skills against a background of mental retardation. This paper reviews the early history and clinical experience with this syndrome, how it unfolds from infancy through adulthood, and how it manifests in different organ systems. Evidence-based recommendations are then offered for the treatment of the specific developmental and medical issues that arise in patients with Williams syndrome.

Williams syndrome: use of chromosomal microdeletions as a tool to dissect cognitive and physical phenotypes

In Williams syndrome (WS), a deletion of approximately 1.5 Mb on one copy of chromosome 7 causes specific physical, cognitive, and behavioral abnormalities. Molecular dissection of the phenotype may be a route to identification of genes important in human cognition and behavior. Among the genes known to be deleted in WS are ELN (which encodes elastin), LIMK1 (which encodes a protein tyrosine kinase expressed in the developing brain), STX1A (which encodes a component of the synaptic apparatus), and FZD3. Study of patients with deletions or mutations confined to ELN showed that hemizygosity for elastin is responsible for the cardiological features of WS. LIMK1 and STX1A are good candidates for cognitive or behavioral aspects of WS. Here we describe genetic and psychometric testing of patients who have small deletions within the WS critical region. Our results suggest that neither LIMK1 hemizygosity (contrary to a previous report) nor STX1A hemizygosity is likely to contribute to any part of the WS phenotype, and they emphasize the importance of such patients for dissecting subtle but highly penetrant phenotypes.

Genes for the CPE receptor (CPETR1) and the human homolog of RVP1 (CPETR2) are localized within the Williams-Beuren syndrome deletion

Williams-Beuren syndrome (WBS) is a neurodevelopmental disorder affecting multiple systems. Haploinsufficiency of genes deleted in chromosomal region 7q11.23 is the likely cause for this syndrome. We now report the localization of the genes for the CPE-R (Clostridium perfringens enterotoxin receptor, CPETR1) and the human homolog of RVP1 (rat ventral prostate 1 protein, CPETR2), both previously mapped to 7q11, to the WBS critical region. A single nucleotide polymorphism (SNP) present in CPETR1 has been identified and was used to determine parental origin of the deleted allele in five informative families. The mouse homologs Cpetr1 and Cpetr2 were identified and mapped to the conserved syntenic region on mouse chromosome 5. Northern blot analysis of CPETR1 demonstrates tissue specificity, with expression in kidney, lung, thyroid, and gastrointestinal tissues. In mouse, Cpetr1 is expressed in the early embryo, appears to be developmentally upregulated during gestation, and is present in adult tissues. Our results suggest a role for CPE-R in internal organ development and function during pre- and postnatal life.

The BCL7 gene family: deletion of BCL7B in Williams syndrome

The BCL7A gene, which maps to human chromosome 12q24.13, was cloned through its direct involvement with MYC and IGH in a three-way translocation in a Burkitt lymphoma cell line. Here, we describe the identification of two related human genes, BCL7B and BCL7C, which share 90% identity to the amino-terminal 51 amino acids of human BCL7A, as well as 41% identity in the same region to Drosophila melanogaster, Caenorhabditis elegans, and Brugia malayi EST sequences. This degree of relatedness in the amino-terminal domain suggests we have defined a new gene family of unknown function. There was little sequence conservation between the family members outside this conserved domain and no identified protein motifs could be deduced. Human BCL7B and BCL7C mapped to chromosome 7q11.23, and 16p11, respectively. No chromosomal rearrangements affecting BCL7B or BCL7C were detected in lymphoid malignancies. BCL7B did, however, map within the region of 7q11.23 which is commonly deleted in the congenital disorder, Williams syndrome.

Inherited duplication Xq27-qter at Xp22.3 in severely affected males: molecular cytogenetic evaluation and clinical description in three unrelated families

We describe the clinical phenotype in four males from three families with duplication (X)(qter-->q27::p22.3-->qter). This is an unusual duplication of the distal long arm segment, Xq27-qter, onto the distal short arm of the X chromosome at Xp22.3, as shown by fluorescent in situ hybridization analysis with multiple X-specific probes. The patients are young male offspring of three unrelated, phenotypically normal carrier women. The affected males have similar clinical manifestations including severe growth retardation and developmental delay, severe axial hypotonia, and minor anomalies. Such clinical similarity in three unrelated families demonstrates that this chromosome abnormality results in a new and distinct clinical phenotype. Replication studies, performed on two of the mothers, provided evidence that inactivation of the abnormal X chromosome permitted the structural abnormality to persist in these families for a generation or more in females without phenotypic expression.

A novel human gene, WSTF, is deleted in Williams syndrome

Williams syndrome (WS) is a developmental disorder caused by deletion of multiple genes at chromosome 7q11.23. Here, we report the identification and characterization of a novel gene, WSTF, that maps to the common WS deletion region. WSTF encodes a novel protein of 1425 amino acids with unknown function. It contains one PHD-type zinc finger motif followed by a bromodomain. Both motifs are found in many transcription regulators, suggesting that WSTF may function as a transcription factor. WSTF is ubiquitously expressed in both adult and fetal tissues. The WSTF gene consists of 20 exons spanning about 80 kb. Fluorescence in situ hybridization analysis shows that WSTF is deleted in 50/50 WS individuals. Hemizygous deletion of WSTF may contribute to WS.

Periodic limb movement in sleep in children with Williams syndrome

OBJECTIVE

Williams syndrome (WS) is associated with neurobehavioral abnormalities that include irritability and attention-deficit/hyperactivity disorder. Parents often report children having difficulties initiating and maintaining sleep because of restlessness and arousals. Therefore we evaluated a group of children with WS for the presence of a movement arousal sleep disorder.

METHODS

Twenty-eight families of children with WS participated in a telephone survey aimed to screen for a movement arousal disorder. Of the 16 children identified as having such a disorder, 7 (mean age, 3.9 +/- 2.2 years) underwent polysomnography. Their studies were compared with those of 10 matched control subjects (mean age, 5.3 +/- 2.0 years).

RESULTS

The 7 subjects with WS who were screened by the survey had sleep latency, total sleep time, arousals, and awakenings that were similar to those of control subjects. However, they presented with a disorder of periodic limb movement in sleep (PLMS). The PLMS index in the subjects with WS was 14.9 +/- 6.2 versus 2.8 +/- 1.9 in control subjects (P < .0001). In addition, arousal and awakening in subjects with WS were strongly associated with PLMS. Moreover, children with WS spend more time awake during sleep periods than control subjects (10.0% +/- 7.0% vs 4.4% +/- 4.7%; P < .05). Five children were treated with clonazepam, and in 4 a significant clinical response was noted.

CONCLUSION

We report an association between WS and PLMS. Clonazepam may reduce the clinical symptoms of PLMS in some of these children.

A novel human gene FKBP6 is deleted in Williams syndrome

Williams syndrome (WS) is a developmental disorder caused by haploinsufficiency of genes at 7q11.23. We have shown that hemizygosity of elastin is responsible for one feature of WS, supravalvular aortic stenosis. We have also implicated LIM-kinase 1 hemizygosity as a contributing factor to impaired visual-spatial constructive cognition in WS. Here we identify and characterize a novel gene, FKBP6, within the common WS deletion region. FKBP6 shows homology to the FK-506 binding protein (FKBP) class of immunophilins. FKBP6 has a putative N-terminal FK-506 binding and peptidylproyl isomerase (rotamase) domain and, like known high-molecular-weight FKBPs, an imperfect C-terminal tetratricopeptide repeat domain. FKBP6 is expressed in testis, heart, skeletal muscle, liver, and kidney. FKBP6 consists of nine exons and is completely contained within a 35-kb cosmid clone. Fluorescence in situ hybridization experiments show that FKBP6 gene is deleted in 40/40 WS individuals. Hemizygous deletion of FKBP6 may contribute to certain defects such as hypercalcemia and growth delay in WS.

A gene-dosage PCR method for the detection of elastin gene deletions in patients with Williams syndrome

Williams syndrome (WS) is a multisystem developmental disorder associated with microdeletions at 7q11.23 that involve several genes, including the elastin gene. Using genomic DNA from a panel of normal individuals and WS patients with established hemizygosity of the elastin gene locus, we have developed a quantitative polymerase chain reaction (PCR)-based gene-dosage assay that rapidly detects the loss of one allele of the elastin gene. Using this procedure, we also studied a family in which the proband was previously diagnosed with WS and her mother with a balanced 7q translocation [t(7:11)(q34;q13)]. Using DNA isolated from buccal smears obtained from several individuals in this family we were able to establish normal disomy at 7q in all family members except for the proband, in which we established hemizygosity at the elastin gene locus. We were also able to successfully infer normal disomy in an unborn child in this family. The rapid diagnostic procedure described here may have a variety of applications, including fine mapping of deletion breakpoints at 7q11.23 associated with WS.

From genetic research into clinical practice

The present genome era is characterized by speedy progress and prompt transfer of results into clinical practice. This creates the need for rapid disclosure of results and renewal of laboratory's protocols. Molecular cytogenetics has provided and increased ability to identify chromosomes, correlate chromosome structure with gene location, find out cryptic aberrations, and detect specific DNA sequences. These advances have allowed the confident discovery of a number of contiguous gene syndromes. The positional cloning and positional candidate strategies have greatly expedited the search process of disease genes, and become relevant methods for genes' discovery. Understanding the molecular basis of diseases has shown an unpredicted wide genetic heterogeneity, which has splitted single disorders into many clinically similar conditions, and added complexity to the nosology of human diseases. The opposite process, allelism, where clinical diversity results from allelic mutations, has lumped together many distinct disorders, by showing that different clinical entities are not necessarily due to mutations in different genes. Dynamic mutations have provided the molecular understanding of interindividual and intrafamilial variability including anticipation, in a number of diseases. The discovery of distinct correlations between the molecular pattern and disease severity is providing a unique opportunity for using molecular results to assess the clinical outcome. Diagnostic, presymptomatic and predictive molecular testing are becoming widely used and provide enormous opportunities for improving the lot of our patients.

The Caenorhabditis elegans unc-64 locus encodes a syntaxin that interacts genetically with synaptobrevin

We describe the molecular cloning and characterization of the unc-64 locus of Caenorhabditis elegans. unc-64 expresses three transcripts, each encoding a molecule with 63-64% identity to human syntaxin 1A, a membrane- anchored protein involved in synaptic vesicle fusion. Interestingly, the alternative forms of syntaxin differ only in their C-terminal hydrophobic membrane anchors. The forms are differentially expressed in neuronal and secretory tissues; genetic evidence suggests that these forms are not functionally equivalent. A complete loss-of-function mutation in unc-64 results in a worm that completes embryogenesis, but arrests development shortly thereafter as a paralyzed L1 larva, presumably as a consequence of neuronal dysfunction. The severity of the neuronal phenotypes of C. elegans syntaxin mutants appears comparable to those of Drosophila syntaxin mutants. However, nematode syntaxin appears not to be required for embryonic development, for secretion of cuticle from the hypodermis, or for the function of muscle, in contrast to Drosophila syntaxin, which appears to be required in all cells. Less severe viable unc-64 mutants exhibit a variety of behavioral defects and show strong resistance to the acetylcholinesterase inhibitor aldicarb. Extracellular physiological recordings from pharyngeal muscle of hypomorphic mutants show alterations in the kinetics of transmitter release. The lesions in the hypomorphic alleles map to the hydrophobic face of the H3 coiled-coil domain of syntaxin, a domain that in vitro mediates physical interactions with similar coiled-coil domains in SNAP-25 and synaptobrevin. Furthermore, the unc-64 syntaxin mutants exhibit allele-specific genetic interactions with mutants carrying lesions in the coiled-coil domain of synaptobrevin, providing in vivo evidence for the significance of these domains in regulating synaptic vesicle fusion.

Mapping of the human cysteine-rich intestinal protein gene CRIP1 to the human chromosomal segment 7q11.23

We report here on the mapping of a cDNA encoding for human cysteine-rich heart protein (HCRHP), a counterpart of the murine cysteine-rich intestinal protein CRIP. By somatic cell hybrid analysis and radiation hybrid mapping, we have located the gene CRIP1 (HGMW-approved symbol) on the subcentromeric region of the q arm of human chromosome 7, flanking a deletion associated with Williams syndrome.

PMS2-related genes flank the rearrangement breakpoints associated with Williams syndrome and other diseases on human chromosome 7

The human PMS2 mismatch repair gene and a family of at least 17 other related genes (named human PMSR or PMS2L genes) have been localized to human chromosome 7. Human PMS2 has been mapped previously to 7p22 and shown to be causative in hereditary nonpolyposis colon cancer (HNPCC), but the human PMS2L genes have not been positioned in the context of the physical or genetic map of chromosome 7. In this study we have used various mapping methodologies to determine the precise location of the human PMS2L genes at 7q11.22, 7q11.23, and 7q22. Within 7q11.23, human PMS2L genes were found to be present at at least three sites as part of duplicated genomic segments that flank the most common rearrangement breakpoints in Williams syndrome.