Investigation of deletions at 7q11.23 in 44 patients referred for Williams-Beuren syndrome, using FISH and four DNA polymorphisms

Genome wide array-CGH and qPCR analysis for the identification of genome defects in Williams' syndrome patients in Saudi Arabia

Background

Williams-Beuren Syndrome (WBS) is a rare neurodevelopmental disorder characterized by dysmorphic features, cardiovascular defects, cognitive deficits and developmental delay. WBS is caused by a segmental aneuploidy of chromosome 7 due to heterozygous deletion of contiguous genes at the long arm of chromosome 7q11.23. We aimed to apply array-CGH technique for the detection of copy number variants in suspected WBS patients and to determine the size of the deleted segment at chromosome 7q11.23 in correlation with the phenotype. The study included 24 patients referred to the CEGMR with the provisional diagnosis of WBS and 8 parents. The patients were subjected to conventional Cytogenetic (G-banding) analysis, Molecular Cytogenetic (Fluorescent In-Situ Hybridization), array-based Comparative Genomic Hybridization (array-CGH) and quantitative Real time PCR (qPCR) Techniques.

Results

No deletions were detected by Karyotyping, however, one patient showed unbalanced translocation between chromosome 18 and 19, the karyotype was 45,XX, der(19) t(18;19)(q11.1;p13.3)-18. FISH technique could detect microdeletion in chromosome 7q11.23 in 10/24 patients. Array-CGH and qPCR confirmed the deletion in all samples, and could detect duplication of 7q11.23 in three patients and two parents. Furthermore, the size of the deletion could be detected accurately by both array-CGH and qPCR techniques. Three patients not showing the 7q11.23 deletion were diagnosed by array-CGH to have deletion in chr9p13.1-p11.2, chr18p11.32-p11.21 and chr1p36.13.

Conclusion

Both FISH and array-CGH are reliable methods for the diagnosis of WBS; however, array-CGH has the advantage of detection of genome deletions/ duplications that cannot otherwise be detected by conventional cytogenetic techniques. Array-CGH and qPCR are useful for detection of deletion sizes and prediction of the interrupted genes and their impact on the disease phenotype. Further investigations are needed for studying the impact of deletion sizes and function of the deleted genes on chromosome 7q11.23.

Trial registration

ISRCTN ISRCTN73824458. MOCY-D-16-00041R1. Registered 28 September 2014. Retrospectively registered.

Copy number variation in Williams-Beuren syndrome: suitable diagnostic strategy for developing countries

Background

Williams-Beuren syndrome (WBS; OMIM 194050) is caused by a hemizygous contiguous gene microdeletion at 7q11.23. Supravalvular aortic stenosis (SVAS), mental retardation, and overfriendliness comprise typical symptoms of WBS. Although fluorescence in situ hybridization (FISH) is considered the gold standard technique, the microsatellite DNA markers and multiplex ligation-dependent probe amplification (MLPA) could be used for to confirm the diagnosis of WBS.

Results

We have evaluated a total cohort of 88 patients with a suspicion clinical diagnosis of WBS using a collection of five markers (D7S1870, D7S489, D7S613, D7S2476, and D7S489_A) and a commercial MLPA kit (P029). The microdeletion was present in 64 (72.7%) patients and absent in 24 (27.3%) patients. The parental origin of deletion was maternal in 36 of 64 patients (56.3%) paternal in 28 of 64 patients (43.7%). The deletion size was 1.55 Mb in 57 of 64 patients (89.1%) and 1.84 Mb in 7 of 64 patients (10.9%). The results were concordant using both techniques, except for four patients whose microsatellite markers were uninformative. There were no clinical differences in relation to either the size or parental origin of the deletion.

Conclusion

MLPA was considered a faster and more economical method in a single assay, whereas the microsatellite markers could determine both the size and parental origin of the deletion in WBS. The microsatellite marker and MLPA techniques are effective in deletion detection in WBS, and both methods provide a useful diagnostic strategy mainly for developing countries.

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

INTRODUCTION

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

OBJECTIVES

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

METHODS

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

RESULTS AND DISCUSSION

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

CONCLUSION

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

Periodontal conditions in Williams Beuren syndrome: a series of 8 cases

BACKGROUND

Williams Beuren syndrome (WBS) is an unusual hereditary connective tissue disease caused by a microdeletion at position 7q11-23 and a haploinsufficiency at the elastin gene. The most frequent specific features are elf-like face, alteration of cognitive functions and cardiovascular diseases including isolated supravalvular aortic stenosis. A number of clinical findings have been reported, but none of the studies evaluating this syndrome consider the oral cavity. It is equally surprising that the gingival tissue, which carries a perfectly structured elastic fibre network, has not yet been investigated. It is important to verify whether subjects affected by WBS are more susceptible to periodontal disease than healthy subjects who are not that much affected, for periodontal disease may have deleterious effects on the cardiovascular system.

METHODS

In an attempt to address this issue, the oral manifestations of 8 patients (ages from 5 to 12 years) with WBS have been investigated: dental examination, periodontal examination (gingival phenotype, plaque control record, gingival index, bone quality).

RESULTS

All patients had oral parafunction, tooth number abnormalities and malocclusions. Average gingival height and width were greater than normal. Plaque index was always very high except for one patient, but the gingival inflammation was not linked to the quantity of clinical plaque index. There was no obvious loss of attachment.

CONCLUSION

As with collagen, elastin is a structural macromolecule of the gingiva. These components play an important role in gingival function and in the resistance of the periodontium to daily aggressions. Unlike genetic diseases characterized by impairment of collagen macrofibrils, it is suggested that the hemizygous gene encoding elastin does not result in periodontal disease. In addition there is an existence of a possible concordance between the elastin gene haploinsufficiency and the periodontal phenotype. There might be some adaptive process to this deficiency.

Williams Syndrome: development of a new scoring system for clinical diagnosis

OBJECTIVE

To develop a scoring system based on clinical findings to assist pediatricians in the diagnosis of William syndrome and to delineate when the fluorescent in-situ hybridization test to detect the microdeletion at 7q11.23 may be needed.

METHODS

The fluorescent in-situ hybridization test was performed on 20 patients presenting William syndrome suggestive clinical features. Eleven studies were selected from the literature in which there were 2 groups: patients with positive or negative fluorescent in-situ hybridization tests. Forty-two clinical characteristics were compared to those reported in the literature to determine which ones were associated with the affected patients (ie, bearing deletions) using meta-analysis. The 2-tailed Fisher exact test were used so that the frequency of findings observed in fluorescent in-situ hybridization positive and fluorescent in-situ hybridization negative patients could be compared in the present study together with the patients from the literature. We developed a scoring system based on clinical findings and their significant associations with patients with positive fluorescent in-situ hybridization tests. From the mean and standard-deviation values of the data from our patients, we determined the cut-off score that that indicated the need for a fluorescent in-situ hybridization test to confirm diagnosis.

RESULTS

Seventeen patients were fluorescent in-situ hybridization positive, and 3 were fluorescent in-situ hybridization negative. The more discriminative findings among fluorescent in-situ hybridization positive patients were the following: typical facies, low birth weight, feeding difficulties, constipation, supravalvar aortic stenosis, mental retardation, and friendly personality. The distribution of the points among the 20 patients ranged from 19 to 28 points with a mean value of 23.3 out of a possible total of 31 points. The cut-off score that indicated the need for a fluorescent in-situ hybridization test was 20.

CONCLUSIONS

Our scoring system enables physicians to differentiate between those individuals who can be reliably diagnosed as having Williams syndrome solely from the clinical findings and those who need to undergo fluorescent in-situ hybridization testing for a correct diagnosis.

Outcome in adult life for people with Williams syndrome-- results from a survey of 239 families

BACKGROUND

Although there has been considerable research into the genotype and phenotype of Williams syndrome, there have been relatively few studies of long-term prognosis. As a preliminary to a more detailed investigation of adults with Williams syndrome, a parental questionnaire was distributed to members of the UK Williams Syndrome Foundation, focusing on areas of skill and difficulties in adult life.

METHOD

A postal questionnaire was distributed to all members of the UK Williams Syndrome Foundation who had a son or daughter aged 18 years or over. The questionnaire covered issues related to the physical and mental health of the adults with Williams syndrome, together with questions about educational and employment status, self-help and independence skills.

RESULTS

Out of a total of 290 questionnaires distributed, 239 were returned (82% response rate). The data highlighted the continuing high rates of physical problems in this group and apparent increases in rates of mental health problems with age. Parents also expressed their concerns about the lack of adequate support and care. Educational and employment attainments were generally low and self-help skills were relatively poor.

DISCUSSION

The findings highlight the need for far better understanding of conditions such as Williams syndrome among professionals working in adult services and the need for more adequate support from educational, health and social services.

Severe infantile hypercalcemia associated with Williams syndrome successfully treated with intravenously administered pamidronate

Infantile hypercalcemia occurs in approximately 15% of children with Williams syndrome (WS) and is typically not clinically severe. We report on 3 children with WS (confirmed with fluorescent in situ hybridization probes) who presented with severe symptomatic hypercalcemia. The first patient's severe hypercalcemia resolved with traditional therapies, whereas the subsequent 2 patients were treated with intravenously administered pamidronate after traditional measures proved only partially successful. Besides asymptomatic mild hypocalcemia, there were no complications resulting from pamidronate administration. We conclude that WS-associated hypercalcemia can be quite severe and symptomatic and that it can be successfully and safely treated with intravenously administered bisphosphonate in some cases.

The elastin gene is disrupted in a family with a balanced translocation t(7;16)(q11.23;q13) associated with a variable expression of the Williams-Beuren syndrome

The Williams-Beuren syndrome (WBS) is a complex developmental disorder with multisystemic manifestations including supravalvular aortic stenosis (SVAS), a so-called elfin face, a hoarse voice, and a specific cognitive phenotype. Most WBS patients have a >1 Mb deletion on one of their chromosomes 7 in q11 but except for elastin, whose haploinsufficiency causes the cardiovascular malformations, it is unknown which genes in the deletion area contribute to the phenotype. We have investigated a family with a cytogenetically balanced translocation t(7;16)(q11.23;q13) in which affected individuals manifested a broad spectrum of clinical phenotypes ranging from a hoarse voice as the only feature to the full WBS phenotype. Molecular cytogenetic and DNA sequence analyses of the translocation breakpoint showed that the cytogenetic rearrangement disrupts the elastin gene locus within intron 5 in the exact same manner in all translocation carriers. The recently described large inversion of the 7q11.23 region was not present in this family. Our data demonstrate that disruption of the elastin gene by a translocation breakpoint may cause classical WBS, atypical WBS, SVAS, or no recognisable phenotype, and provide a clear example for extensive phenotypic variability associated with a position effect in humans.

Brain imaging in neurogenetic conditions: realizing the potential of behavioral neurogenetics research

Behavioral neurogenetics research is a new method of scientific inquiry that focuses on investigation of neurodevelopmental dysfunction associated with specific genetic conditions. This research method provides a powerful tool for scientific inquiry into human gene-brain-behavior linkages that complements more traditional research approaches. In particular, the use of specific genetic conditions as models of common behavioral and cognitive disorders occurring in the general population can reveal insights into neurodevelopmental pathways that might otherwise be obscured or diluted when investigating more heterogeneous, behaviorally defined subject groups. In this paper, we review five genetic conditions that commonly give rise to identifiable neurodevelopmental and neuropsychiatric disability in children: fragile X syndrome, velo-cardio-facial syndrome, Williams syndrome, Turner syndrome, and Klinefelter syndrome. While emphasis is placed on describing the brain morphology associated with these conditions as revealed by neuroimaging studies, we also include information pertaining to molecular genetic, postmortem, and neurobehavioral investigations to illustrate how behavioral neurogenetics research can contribute to an improved understanding of brain disorders in childhood.

Diagnosis of DiGeorge and Williams syndromes using FISH analysis of peripheral blood smears

We describe the use of a FISH protocol for detecting chromosome microdeletions in peripheral blood smear leukocytes. This method has the advantage of a smaller sample requirement than classical metaphase chromosome analysis and the potential for analysis of a larger number of chromosome microdeletions using a routine blood smear. A selected series of 10 DiGeorge syndrome (DGS) and 12 Williams-Beuren syndrome (WBS) patients were correctly diagnosed by this method confirming results obtained by molecular cytogenetic metaphases. These results support effectiveness of interphase FISH analysis on peripheral blood smears as a focused, single-step method for the detection of chromosome microdeletions.