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Array-CGH analysis in Rwandan patients presenting development delay/intellectual disability with multiple congenital anomalies.

ABSTRACT: BACKGROUND: Array-CGH is considered as the first-tier investigation used to identify copy number variations. Right now, there is no available data about the genetic etiology of patients with development delay/intellectual disability and congenital malformation in East Africa. METHODS: Array comparative genomic hybridization was performed in 50 Rwandan patients with development delay/intellectual disability and multiple congenital abnormalities, using the Agilent's 180 K microarray platform. RESULTS: Fourteen patients (28%) had a global development delay whereas 36 (72%) patients presented intellectual disability. All patients presented multiple congenital abnormalities. Clinically significant copy number variations were found in 13 patients (26%). Size of CNVs ranged from 0,9 Mb to 34 Mb. Six patients had CNVs associated with known syndromes, whereas 7 patients presented rare genomic imbalances. CONCLUSION: This study showed that CNVs are present in African population and show the importance to implement genetic testing in East-African countries.

SUBMITTER: Uwineza A

PROVIDER: S-EPMC4123504 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Array-CGH analysis in Rwandan patients presenting development delay/intellectual disability with multiple congenital anomalies.

Uwineza Annette A Caberg Jean-Hubert JH Hitayezu Janvier J Hellin Anne Cecile AC Jamar Mauricette M Dideberg Vinciane V Rusingiza Emmanuel K EK Bours Vincent V Mutesa Leon L

BMC medical genetics 20140712

<h4>Background</h4>Array-CGH is considered as the first-tier investigation used to identify copy number variations. Right now, there is no available data about the genetic etiology of patients with development delay/intellectual disability and congenital malformation in East Africa.<h4>Methods</h4>Array comparative genomic hybridization was performed in 50 Rwandan patients with development delay/intellectual disability and multiple congenital abnormalities, using the Agilent's 180 K microarray p ...[more]

PMID: 25016475

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Project description:UNLABELLED: BACKGROUND: Array comparative genomic hybridization (CGH) has been repeatedly shown to be a successful tool for the identification of genomic variations in a clinical population. During the last decade, the implementation of array CGH has resulted in the identification of new causative submicroscopic chromosome imbalances and copy number variations (CNVs) in neuropsychiatric (neurobehavioral) diseases. Currently, array-CGH-based technologies have become an integral part of molecular diagnosis and research in individuals with neuropsychiatric disorders and children with intellectual disability (mental retardation) and congenital anomalies. Here, we introduce the Russian cohort of children with intellectual disability, autism, epilepsy and congenital anomalies analyzed by BAC array CGH and a novel bioinformatic strategy. RESULTS: Among 54 individuals highly selected according to clinical criteria and molecular and cytogenetic data (from 2426 patients evaluated cytogenetically and molecularly between November 2007 and May 2012), chromosomal imbalances were detected in 26 individuals (48%). In two patients (4%), a previously undescribed condition was observed. The latter has been designated as meiotic (constitutional) genomic instability resulted in multiple submicroscopic rearrangements (including CNVs). Using bioinformatic strategy, we were able to identify clinically relevant CNVs in 15 individuals (28%). Selected cases were confirmed by molecular cytogenetic and molecular genetic methods. Eight out of 26 chromosomal imbalances (31%) have not been previously reported. Among them, three cases were co-occurrence of subtle chromosome 9 and 21 deletions. CONCLUSIONS: We conducted an array CGH study of Russian patients suffering from intellectual disability, autism, epilepsy and congenital anomalies. In total, phenotypic manifestations of clinically relevant genomic variations were found to result from genomic rearrangements affecting 1247 disease-causing and pathway-involved genes. Obviously, a significantly lesser part of them are true candidates for intellectual disability, autism or epilepsy. The success of our preliminary array CGH and bioinformatic study allows us to expand the cohort. According to the available literature, this is the first comprehensive array CGH evaluation of a Russian cohort of children with neuropsychiatric disorders and congenital anomalies.

Project description:We aimed to define a novel autosomal recessive neurodevelopmental disorder, characterize its clinical features, and identify the underlying genetic cause for this condition. Clinical and genetic data from affected individuals with neurological disorders were matched across families from five global sites. Here, we report five recessive CSPG4 (NM_001897) missense variants [three homozygous: c.A1370G (p.Asp457Gly), c.2627G>A (p.Arg876His) and c.3247C>A (p.Gln1083Lys), and two compound heterozygote: c.A1370G and c.5156A>G (p.Asp457Gly and p.Gln1719Arg) and c.658A>G and c.1220_1221delinsTG (p.(Thr220Ala and p.Pro407Leu)] by next-generation sequencing of five unrelated families with seven affected subjects. All subjects share a novel neurodevelopmental syndrome characterized by severe intellectual disability, global developmental delay, delayed ability to walk, speech and language delay, distinctive facial features, along with varying degrees of neurological impairment, including hypotonia, cerebellar hypoplasia, and/or seizures. All CSPG4 variants were predicted to be damaging using in silico tools, and three-dimensional molecular modeling suggested significant alterations in protein stability, compromising inter- and intra-molecular interactions. The impact on neurological and craniofacial development was analyzed in CRISPR/Cas9-mediated zebrafish models. CSPG4 variants affected notochord development, neuronal function, and cerebellar structure along with a disorganized head scaffold with anomalous skeletal and cartilage components. Two individuals metabolomics and crispant transcriptomics revealed significant perturbation of metabolites, extracellular matrix (ECM) regulating pathways, and genes previously described to cause mental retardation, dwarfism, and facial anomalies in humans. Our study links novel, rare, damaging variants of the ECM gene CSPG4 to a novel recessive Mendelian neurodevelopmental disorder in humans and supports the role of CSPG4 in early development.

Project description:Intellectual Disability (ID) is a neurodevelopmental disorder that affects approximately 3% of children and adolescents worldwide. It is a heterogeneous and multifactorial clinical condition. Several methodologies have been used to identify the genetic causes of ID and in recent years new generation sequencing techniques, such as exome sequencing, have enabled an increase in the detection of new pathogenic variants and new genes associated with ID. The aim of this study was to evaluate exome sequencing with analysis of the ID gene panel as a tool to increase the diagnostic yield of patients with ID/GDD/MCA in Central Brazil, together with karyotype and CMA tests. A retrospective cohort study was carried out with 369 patients encompassing both sexes. Karyotype analysis was performed for all patients. CMA was performed for patients who did not present structural and or numerical alterations in the karyotype. Cases that were not diagnosed after performing karyotyping and CMA were referred for exome sequencing using a gene panel for ID that included 1,252 genes. The karyotype identified chromosomal alterations in 34.7% (128/369). CMA was performed in 83 patients who had normal karyotype results resulting in a diagnostic yield of 21.7% (18/83). Exome sequencing with analysis of the ID gene panel was performed in 19 trios of families that had negative results with previous methodologies. With the ID gene panel analysis, we identified mutations in 63.1% (12/19) of the cases of which 75% (9/12) were pathogenic variants,8.3% (1/12) likely pathogenic and in 16.7% (2/12) it concerned a Variant of Uncertain Significance. With the three methodologies applied, it was possible to identify the genetic cause of ID in 42.3% (156/369) of the patients. In conclusion, our studies show the different methodologies that can be useful in diagnosing ID/GDD/MCA and that whole exome sequencing followed by gene panel analysis, when combined with clinical and laboratory screening, is an efficient diagnostic strategy.

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Array-CGH analysis in Rwandan patients presenting development delay/intellectual disability with multiple congenital anomalies.

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Array-CGH analysis in Rwandan patients presenting development delay/intellectual disability with multiple congenital anomalies.

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