Overcoming challenges for the unambiguous detection of copy number variations is essential to broaden our understanding of the role of genomic variants in the clinical phenotype. With the improvement ...of software and databases, whole-exome sequencing quickly can become an excellent strategy in the routine diagnosis of patients with a developmental delay and/or multiple congenital malformations. However, even after a detailed analysis of pathogenic single-nucleotide variants and indels in known disease genes, using whole-exome sequencing, some patients with suspected syndromic conditions are left without a conclusive diagnosis. These negative results could be the result of different factors including nongenetic etiologies, lack of knowledge about the genes that cause different disease phenotypes, or, in some cases, a deletion or duplication of genomic information not routinely detectable by whole-exome sequencing variant calling. Although copy number variant detection is possible using whole-exome sequencing data, such analysis presents significant challenges and cannot yet be used to replace chromosomal arrays for identification of deletions or duplications.
The most prevalent structural variations in the human genome are copy number variations (CNVs), which appear predominantly in the subtelomeric regions. Variable sizes of 4p/4q CNVs have been ...associated with several different psychiatric findings and developmental disability (DD). We analyzed 105 patients with congenital anomalies (CA) and developmental and/or intellectual disabilities (DD/ID) using MLPA subtelomeric specific kits (P036 /P070) and 4 of them using microarrays. We found abnormal subtelomeric CNVs in 15 patients (14.3%), including 8 patients with subtelomeric deletions at 4p/4q (53.3%). Additional genomic changes were observed at 1p36, 2q37.3, 5p15.3, 5q35.3, 8p23.3, 13q11, 14q32.3, 15q11.2, and Xq28/Yq12. This indicates the prevalence of independent deletions at 4p/4q, involving PIGG, TRIML2, and FRG1. Furthermore, we identified 15 genes with changes in copy number that contribute to neurological development and/or function, among them CRMP1, SORCS2, SLC25A4, and HELT. Our results highlight the association of genes with changes in copy number at 4p and 4q subtelomeric regions and the DD phenotype. Cytogenomic characterization of additional cases with distal deletions should help clarifying the role of subtelomeric CNVs in neurological diseases.
Background
Cri du chat syndrome (CdCS) is a rare syndrome caused by a partial or complete deletion of the short arm of chromosome 5 (5p‐). The main clinical features include a high‐pitched cry, ...facial asymmetry, microcephaly, round face at birth, epicanthal folds, hypotonia, delayed growth and development.
Methods
We studied 14 Brazilian patients with CdCS using genomic array in order to better define the 5p breakpoints and recognize copy number variations (CNVs) that contribute to clinical manifestations associated with the syndrome.
Results
Array confirmed terminal deletions in 13 patients and an interstitial deletion in one patient. It was also possible to map the breakpoints and associate a genomic region of 4.7 Mb to the development of head circumference and cat‐like cry. We also found other CNVs concomitant to the 5p deletion including a 9p duplication, a 17q deletion, and a 22q deletion in three different patients.
Conclusion
With advancements of molecular cytogenomic methods in the last two decades, it was possible to evidence cryptic alterations and improve the genotype–phenotype correlation. In this work, we describe a new genomic region associated with microcephaly and cat‐like cry and highlight the importance of precise delineation of 5p deletion breakpoints and detection of other CNVs in CdCS patients to improve genotype–phenotype correlation to perform a complete clinical and molecular diagnosis.
We studied 14 Brazilian patients with Cri du chat syndrome using arrays and suggest a new genomic region associated with microcephaly and cat‐like cry. Also we highlight the importance of precise delineation of 5p deletion breakpoints for better genotype–phenotype correlation.
Abstract
Context
The genetic bases of osteoporosis (OP), a disorder with high heritability, are poorly understood at an individual level. Cases of idiopathic or familial OP have long puzzled ...clinicians as to whether an actionable genetic cause could be identified.
Objective
We performed a genetic analysis of 28 cases of idiopathic, severe, or familial osteoporosis using targeted massively parallel sequencing.
Design
Targeted sequencing of 128 candidate genes was performed using Illumina NextSeq. Variants of interest were confirmed by Sanger sequencing or SNP array.
Patients and Setting
Thirty-seven patients in an academic tertiary hospital participated (54% male; median age, 44 years; 86% with fractures), corresponding to 28 sporadic or familial cases.
Main Outcome Measure
The identification of rare stop-gain, indel, splice site, copy-number, or nonsynonymous variants altering protein function.
Results
Altogether, we identified 28 variants of interest, but only 3 were classified as pathogenic or likely pathogenic variants: COL1A2 p.(Arg708Gln), WNT1 p.(Gly169Asp), and IDUA p.(His82Gln). An association of variants in different genes was found in 21% of cases, including a young woman with severe OP bearing WNT1, PLS3, and NOTCH2 variants. Among genes of uncertain significance analyzed, a potential additional line of evidence has arisen for GWAS candidates GPR68 and NBR1, warranting further studies.
Conclusions
While we hope that continuing efforts to identify genetic predisposition to OP will lead to improved and personalized care in the future, the likelihood of identifying actionable pathogenic variants in intriguing cases of idiopathic or familial osteoporosis is seemingly low.
Background
Bloom syndrome (BS) is a rare autosomal recessive chromosome instability disorder. The main clinical manifestations are growth deficiency, telangiectasic facial erythema, immunodeficiency, ...and increased risk to develop neoplasias at early age. Cytogenetic test for sister chromatid exchanges (SCEs) is used as a diagnostic marker for BS. In addition, most patients also present mutations in the BLM gene, related to defects in the DNA repair mechanism. However, the molecular mechanism behind the pathogenicity of BS is still not completely understood.
Methods
We describe two patients confirmed with BS by SCE and molecular analysis. Also, we performed the gene expression profile by the RNA‐seq methodology in mRNA transcripts for differential gene expression analysis using as a biological condition for comparison BS versus health controls.
Results
We detected 216 differentially expressed genes related to immunological pathways such as positive regulation and activation of B cells, immune effector process and absence of difference of DNA repair genes expression. In addition; we also observed differentially expressed genes associated with apoptosis control, such as BCL2L1, CASP7, CDKN1A, E2F2, ITPR, CD274, TNFAIP6, TNFRSF25, TNFRSF13C, and TNFRSF17.
Conclusion
Our results suggest that the combination of altered expression of genes involved in signaling pathways of immune response and apoptosis control may contribute directly to the main characteristics observed in BS, such as recurrent infections, growth failure, and high risk of cancer. Transcriptome studies of other instability syndromes could allow a more accurate analysis of the relevant gene interactions associated with the destabilization of the genome. This is a first description of the profile of differential gene expression related to immunological aspects detected in patients with BS by RNA‐seq.
We investigate two patients with Bloom´s syndrome that presented immunological deficiency that was confirm by differential gene expression analysis by RNA‐seq using Illumina platform. The analysis showed an unexpected highly complex transcriptional profile with downregulated differentially expressed genes associated to activation and regulation of immune pathways and absence of difference of DNA repair genes. This is a first description of the profile of differential gene expression related to immunological aspects detected in patients with SB by RNA‐seq.
Genomic rearrangements encompass deletions, duplications, inversions, insertions and translocations and may be the cause of several genetic diseases. One of the most frequent mechanisms that generate ...these rearrangements is the Non-Allelic Homologous Recombination (NAHR). They are caused by a misalignment between regions of high level of similarity, like Low Copy Repeats (LCRs) and Alu sequences. We aimed to sequence the breakpoint of a patient with a single deletion on chromosome 22q13.2 in order to understand the genomic structure of the region involved as well as elucidate the mechanism behind this rearrangement. Investigating breakpoints are of the utmost importance in the understanding the influence of the genomic architecture in clinical assays. We flanked the breakpoint detected by array and then we captured the regions using Illumina Nextera Rapid Capture Custom to sequence with Illumina MiSeq. We found a chimeric read on Chr22:41,026,090, setting a 624,688 bp deletion on Chr22:41,026,112-41,650,780 (hg19). This deletion merges the intronic region of MKL1 and RANGAP1 genes, on two different Alu sequences (AluSx and AluY, respectively). The sequence of the breakpoint reveals that Alu elements are an important characteristic of the human genome on generating rearrangements.
•We investigated the breakpoint on chromosome 22q13.2 in order to understand the genomic structure of the region involved as well as elucidate the mechanism behind this rearrangement.•Our results showed that the breakpoint is inserted in two different Alu regions and the absence of micro-homology inside the breakpoint, lead us to consider NAHR mechanism driven by Alu. It is the first time that a fusion between MKL1 and RANGAP1 genes are sequenced.•Delineate breakpoints is important to understanding the influence of the genomic architecture in clinical assays.
To report the effectiveness of early molecular diagnosis in the clinical management of rare diseases, presenting 8 patients with 8p23.1DS who have clinical features that overlap the phenotypic ...spectrum of 22q11.2DS.
This report is part of a previous study that aims to provide a precocious molecular diagnosis of the 22q11.2 deletion syndrome in 118 infants with congenital heart disease. To confirm the clinical diagnosis, patients underwent comparative genomic screening by the multiplex ligation-dependent probe amplification (MLPA) assay with the SALSA MLPA probemix kits P064-B2, P036-E1, P070-B2, P356-A1, and P250- B1. Subsequently, the patients performed the genomic microarray using the Infinium CytoSNP-850K BeadChip to confirm the deletion, determine the breakpoints of the deletion, and search for genomic copy number variations.
MLPA performed with 3 different kits revealed the 8p23.1 typical deletion involving the PPP1R3B, MSRA, and GATA4 genes in the 5 patients. The array analysis was performed on these 5 patients and 3 other patients (8 patients) who also had clinical suspicion of 22q11 deletion (8 patients) allowed a precise definition of the breakpoints and excluded other genomic abnormalities.
Cytogenomic screening was efficient in establishing a differential diagnosis and ruling out the presence of other concomitant syndromes. The clinical picture of the 8p23.1 deletion syndrome is challenging; however, cytogenomic tools can provide an exact diagnosis and help to clarify the genotype-phenotype complexity of these patients. Our reports underline the importance of early diagnosis and clinical follow-up of microdeletion syndromes.
The human genome contains several types of variations, such as copy number variations, that can generate specific clinical abnormalities. Different techniques are used to detect these changes, and ...obtaining an unequivocal diagnosis is important to understand the physiopathology of the diseases. The objective of this study was to assess the diagnostic capacity of multiplex ligation-dependent probe amplification and array techniques for etiologic diagnosis of syndromic patients.
We analyzed 93 patients with developmental delay and multiple congenital abnormalities using multiplex ligation-dependent probe amplifications and arrays.
Multiplex ligation-dependent probe amplification using different kits revealed several changes in approximately 33.3% of patients. The use of arrays with different platforms showed an approximately 53.75% detection rate for at least one pathogenic change and a 46.25% detection rate for patients with benign changes. A concomitant assessment of the two techniques showed an approximately 97.8% rate of concordance, although the results were not the same in all cases. In contrast with the array results, the MLPA technique detected ∼70.6% of pathogenic changes.
The obtained results corroborated data reported in the literature, but the overall detection rate was higher than the rates previously reported, due in part to the criteria used to select patients. Although arrays are the most efficient tool for diagnosis, they are not always suitable as a first-line diagnostic approach because of their high cost for large-scale use in developing countries. Thus, clinical and laboratory interactions with skilled technicians are required to target patients for the most effective and beneficial molecular diagnosis.
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