Two heterozygous mutations in the ERCC6 gene associated with Cockayne syndrome in a Chinese patient.
ABSTRACT: OBJECTIVE:To confirm diagnosis and explore the genetic aetiology in a Chinese patient suspected to have Cockayne syndrome (CS). METHODS:The patient was clinically examined, and the patient and her biological parents underwent genetic analysis using whole exome sequencing (WES) and Sanger sequencing. The foetus of the patient's mother underwent prenatal diagnostic Sanger sequencing using amniotic fluid obtained at 19 weeks' gestation. RESULTS:Clinical examination of the patient showed developmental delay, progressive neurologic dysfunction and premature aging. Two compound, heterozygous ERCC excision repair 6, chromatin remodelling factor (ERCC6) gene mutations were detected in the proband by WES and confirmed by Sanger sequencing, comprising a known paternal nonsense mutation (c.643G?>?T, p.E215X) and a novel maternal short insertion and deletion mutation (c.1614_c.1616delGACinsAAACGTCTT, p.K538_T539delinsKNVF). The patient was consequently diagnosed with CS type I. The foetus of the patient's mother was found to carry only the maternally-derived c.1614_c.1616delGACinsAAACGTCTT variant. CONCLUSION:This study emphasized the value of WES in clinical diagnosis, and enriched the known spectrum of ERCC6 gene mutations.
Project description:Cockayne syndrome (CS) is a rare autosomal recessive disorder, the primary manifestations of which are poor growth and neurologic abnormality. Mutations of the ERCC6 and ERCC8 genes are the predominant cause of Cockayne syndrome, and the ERCC6 gene mutation is present in approximately 65% of cases. The present report describes a case of Cockayne syndrome in a Chinese family, with the patients carrying two missense mutations (c.1595A>G, p.Asp532Gly and c.1607T>G, p.Leu536Trp) in the ERCC6 gene in an apparently compound heterozygote status, especially, p.Asp532Gly has never been reported. The compound heterozygote mutation was found in three patients in the family using whole exome sequencing. The patients' father and mother carried a heterozygous allele at different locations of the ERCC6 gene, which was confirmed by Sanger DNA sequencing. The two mutations are both located in the highly conserved motif I of ATP-binding helicase and are considered "Damaging," "Probably Damaging," "Disease Causing," and "Conserved", indicating the role of DNA damage in the pathogenetic process of the disease. The results not only enrich the ERCC6 mutations database, but also indicate that whole exome sequencing will be a powerful tool for discovering the disease causing mutations in clinical diagnosis.
Project description:Accurate molecular diagnosis of monogenic non-autoimmune neonatal diabetes mellitus (NDM) is critical for patient care, as patients carrying a mutation in KCNJ11 or ABCC8 can be treated by oral sulfonylurea drugs instead of insulin therapy. This diagnosis is currently based on Sanger sequencing of at least 42 PCR fragments from the KCNJ11, ABCC8, and INS genes. Here, we assessed the feasibility of using the next-generation whole exome sequencing (WES) for the NDM molecular diagnosis.We carried out WES for a patient presenting with permanent NDM, for whom mutations in KCNJ11, ABCC8 and INS and abnormalities in chromosome 6q24 had been previously excluded. A solution hybridization selection was performed to generate WES in 76 bp paired-end reads, by using two channels of the sequencing instrument. WES quality was assessed using a high-resolution oligonucleotide whole-genome genotyping array. From our WES with high-quality reads, we identified a novel non-synonymous mutation in ABCC8 (c.1455G>C/p.Q485H), despite a previous negative sequencing of this gene. This mutation, confirmed by Sanger sequencing, was not present in 348 controls and in the patient's mother, father and young brother, all of whom are normoglycemic.WES identified a novel de novo ABCC8 mutation in a NDM patient. Compared to the current Sanger protocol, WES is a comprehensive, cost-efficient and rapid method to identify mutations in NDM patients. We suggest WES as a near future tool of choice for further molecular diagnosis of NDM cases, negative for chr6q24, KCNJ11 and INS abnormalities.
Project description:BACKGROUND:Cockayne Syndrome (CS) is a rare autosomal recessive disorder characterized by neurological and sensorial impairment, dwarfism, microcephaly and photosensitivity. CS is caused by mutations in ERCC6 (CSB) or ERCC8 (CSA) genes. METHODS:Three patients with CS were referred to the Medical Genetics Unit of Saint Joseph University. Sanger sequencing of both ERCC8 and ERCC6 genes was performed: ERCC8 was tested in all patients while ERCC6 in one of them. RESULTS:Sequencing led to the identification of three homozygous mutations, two in ERCC8 (p.Y322* and c.843?+?1G?>?C) and one in ERCC6 (p.R670W). All mutations were previously reported as pathogenic except for the c.843?+?1G?>?C splice site mutation in ERCC8 which is novel. CONCLUSIONS:Molecular diagnosis was established in all patients included in our study. A genotype-phenotype correlation is discussed and a link, between mutations and some specific religious communities in Lebanon, is suggested.
Project description:Renal hypouricemia (RHUC) is a heterogeneous genetic disorder that is characterized by decreased serum uric acid concentration and increased fractional excretion of uric acid. Previous reports have revealed many functional mutations in two urate transporter genes, SLC22A12 and/or SLC2A9, to be the causative genetic factors of this disorder. However, there are still unresolved patients, suggesting the existence of other causal genes or new mutations. Here, we report an RHUC patient with novel compound heterozygous mutations in the SLC22A12 gene.A 27-year-old female presenting with recurrent hypouricemia during routine checkups was referred to our hospital. After obtaining the patient's consent, both the patient and her healthy parents were analyzed using whole-exome sequencing (WES) and Sanger sequencing to discover and validate causal mutations, respectively. The prioritization protocol of WES screened out two mutations of c.269G?>?A/p.R90H and c.1289_1290insGG/p.M430fsX466, which are both located in the SLC22A12 gene, in the patient. Sanger sequencing further confirmed that the patient's heterozygous c.269G?>?A/p.R90H mutation, which has been reported previously, derived from her mother, and the heterozygous c.1289_1290insGG/p.M430fsX466 mutation, which was found for the first time, derived from her father. p.R90H, which is highly conserved among different species, may decrease the stability of this domain and was considered to be almost damaging in silicon analysis. p.M430fsX466 lacks the last three transmembrane domains, including the tripeptide motif (S/T)X? (X?=?any amino acid and ??=?hydrophobic residue), at the C-terminal, which interact with scaffolding protein PDZK1 and thus will possibly lead to weak functioning of urate transport through the disruption of the "transporter complex" that is formed by URAT1 and PDZK1.We report a Chinese patient with RHUC, which was caused by compound heterozygous mutations of the SLC22A12 gene, using WES and Sanger sequencing for the first time. Mutation-induced structural instability or malfunction of the urate transporter complex may be the main mechanisms for this hereditary disorder.
Project description:Cockayne syndrome (CS) is a rare multisystemic autosomal recessive disease. The primary manifestations of which are developmental delay, neurological impairment, abnormal skin sensitivity to sunlight and unique facial appearance as sunken eyes, large ears, and thin large nose. The disorders of the nucleotide excision repair system significantly are caused by mutations of Excision repair cross-complementing group 6 (ERCC6) and Excision repair cross-complementing group 8 (ERCC8) genes, and the ERCC6 gene mutations are present in approximately 65% of cases.Here we described a girl in a consanguineous Jordanian family with abnormal facial appearance and postnatal growth delay. She was not able to gain weight. Her condition deteriorated progressively and she developed difficulty of swallowing even to water. The patient was diagnosed as CS based on her facial appearance and neurologic dysfunction. The patient was examined at 3 years old, and died at 4 years old.Genetic analysis and sequencing revealed homozygosity for a novel frame shift mutation c.2911_2915del5ins9 (p.Lys971TryfsX14) in the ERCC6. The mutation is predicted to delete 5 nucleotides and add 9 nucleotides with a premature termination, resulting in approximately 34% length reduction of the wild-type transcript. The multisystem malformations of CS are clinically heterogeneous. The frame shift mutation of ERCC6 found in this patient is a novel one, which caused postnatal growth failure and early death. Our findings indicate truncated mutation in CS lead to more severe CS phenotype and add to the genotype-phenotype correlations in CS.
Project description:<h4>Objective</h4>To identify causative mutations in a patient affected by ataxia and spastic paraplegia.<h4>Methods</h4>Whole-exome sequencing (WES) and whole-genome sequencing (WGS) were performed using patient's DNA sample. RT-PCR and cDNA Sanger sequencing were performed on RNA extracted from patient's fibroblasts, as well as western blot.<h4>Results</h4>A novel missense variant in SPG7 (c.2195T> C; p.Leu732Pro) was first found by whole-exome sequencing (WES), while the second, also unreported, deep intronic variant (c.286 + 853A>G) was identified by whole-genome sequencing (WGS). RT-PCR confirmed the in silico predictions showing that this variant activated a cryptic splice site, inducing the inclusion of a pseudoexon into the mRNA sequence, which encoded a premature stop codon. Western blot showed decreased SPG7 levels in patient's fibroblasts.<h4>Interpretation</h4>Identification of a deep intronic variant in SPG7, which could only have been detected by performing WGS, led to a diagnosis in this HSP patient. This case challenges the notion of an autosomal dominant inheritance for SPG7, and illustrates the importance of performing WGS subsequently or alternatively to WES to find additional mutations, especially in patients carrying one variant in a gene causing a predominantly autosomal recessive disease.
Project description:Background: Genetic studies of late-onset sporadic ataxias (>40 years of age) are not routinely indicated. For unresolved cases, next-generation sequencing (NGS) tools, such as whole-exome sequencing (WES), are available for a definitive diagnosis. Case presentation: Our patient is a woman with a usual facial phenotype and anthropometry, who developed ataxia at 45 years of age, with no relevant family history and an initial clinical approach that ruled out common aetiologies. WES was performed when the patient was 54 years old. The results identified the heterozygous pathogenic variant c.248delA (p.N83MfsX4) in the nuclear receptor-binding SET domain protein 1 (NSD1; MIM 606681) gene (related to Sotos syndrome), which was not associated with ataxia and is not related to the patient's phenotype. Sanger sequencing of NSD1 in two different laboratories confirmed the variant. Conclusions: NGS findings generally offer valuable information that can be used for clinical decision-making. However, an incidental finding that leads to defining new clinical and bioethical actions is also possible. Consequently, the biological importance of this type of genetic "incidentalome" must be determined.
Project description:Purpose:Ectodermal dysplasias are characterized by developmental abnormalities in ectodermal structures. Hypohidrotic ectodermal dysplasias (HED) are the most common subtype. They are most commonly inherited via X-linked recessive routes. We report on a novel ectodysplasin-A (EDA) mutation that is expected to be involved in pathogenesis of HED. Methods:Hypohidrotic ectodermal dysplasia genes, including EDA, EDAR and EDARADD, were analyzed using next-generation sequencing (NGS). The detected mutation on the EDA gene was confirmed in the patient and his mother using Sanger sequencing. Results:The patient presented with adontia, absence of gum development, hyperthermia and hypohidrosis. Our genetic analysis of the patient revealed a novel frameshift hemizygous mutation (c.898_924?+?8del35ins4CTTA) on the EDA gene. The patient's mother showed a mild HED phenotype. Direct sequencing of the EDA gene in the region where her son had the mutation showed the same mutation in a heterozygous state. Conclusion:We identified a novel frameshift mutation in the EDA gene in an Iranian patient affected by X-linked HED. The difference between our patient's symptoms and those recorded for some previous subjects may be due to the differences in the mutations involved.
Project description:Sanger sequencing, the traditional "gold standard" for mutation detection, has been wildly used in genetic testing of pulmonary artery hypertension (PAH). However, with the advent of whole-exome sequencing (WES), few studies have compared the accuracy of WES and Sanger sequencing in routine genetic testing of PAH. PAH individuals were enrolled from Fu Wai Hospital and Shanghai Pulmonary Hospital. WES was used to analyze DNA samples from 120 PAH patients whose bone morphogenetic protein receptor type 2 (BMPR2) mutation statuses had been previously studied using Sanger sequencing. The Sanger sequencing and WES agreement was 98.3% (118/120) with near-perfect agreement (? coefficient?=?0.848). There was no significant difference between the two methods on the McNemar-Bowker test ( P?>?0.05). Twenty-one BMPR2 mutation carriers and 99 non-carriers were detected by Sanger sequencing. Among the 21 BMPR2 carriers detected by Sanger sequencing, one variant (c.1040 T?>?A) was not found by WES. Among the 99 BMPR2 non-carriers, WES detected an extra mutation carrier (c.76?+?1 G?>?C) missed by Sanger sequencing. Both false-positive and false-negative results were highly conserved and were re-analyzed by Sanger sequencing. WES improved the accuracy of Sanger sequencing and detected 1% (1/99) false-positive and 4.8% (1/21) false-negative results of Sanger sequencing. No false-positive and false-negative results of WES were identified in our analysis. WES is non-inferior to Sanger sequencing and may play a more important role in genetic testing of PAH patients in the future.
Project description:We describe both phenotype and pathogenesis in two male siblings with typical retinitis pigmentosa (RP) and the potentially X-linked RP (XLRP) carrier phenotype in their mother. Two affected sons, two unaffected daughters, and their mother underwent detailed ophthalmological assessments including Goldmann perimetry, color vision testing, multimodal imaging and ISCEV-standard electroretinography. Genetic testing consisted of targeted next-generation sequencing (NGS) of known XLRP genes and whole exome sequencing (WES) of known inherited retinal disease genes (RetNet-WES). Variant validation and segregation analysis were performed by Sanger sequencing. The mutational load of the RHO variant in the mother was assessed in DNA from leucocytes, buccal cells and hair follicles using targeted NGS. Both affected sons showed signs of classical RP, while the mother displayed patches of hyperautofluorescence on blue light autofluorescence imaging and regional, intraretinal, spicular pigmentation, reminiscent of a carrier phenotype of XLRP. XLRP testing was negative. RetNet-WES testing revealed RHO variant c.404G?>?C p.(Arg135Pro) in a mosaic state (21% of the reads) in the mother and in a heterozygous state in both sons. Targeted NGQSS of the RHO variant in different maternal tissues showed a mutation load between 25.06% and 41.72%. We report for the first time that somatic mosaicism of RHO variant c.404G?>?C p.(Arg135Pro) mimics the phenotype of a female carrier of XLRP, in combination with heterozygosity for the variant in the two affected sons.