Mixed Dubin-Gilbert Syndrome: A Compound Heterozygous Phenotype of Two Novel Variants in ABCC2 Gene.
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ABSTRACT:
SUBMITTER: Jiang J
PROVIDER: S-EPMC5407029 | biostudies-literature | 2017 Apr
REPOSITORIES: biostudies-literature
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Mixed Dubin-Gilbert Syndrome: A Compound Heterozygous Phenotype of Two Novel Variants in <i>ABCC2</i> Gene.
Jiang Jun J Wang Hua-Gui HG Wu Wei-Li WL Peng Xiang-Xin XX
Chinese medical journal 20170401 8
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Project description:Background: Dubin-Johnson syndrome (DJS) is a rare autosomal recessive genetic disease which is caused by mutations in the ABCC2 gene; it is characterized by chronic hyperbilirubinemia. Here, we report two pedigrees affected with DJS which were caused by three novel pathogenic ABCC2 mutations. Case summary: The two patients exhibited intermittent low-grade, predominantly conjugated hyperbilirubinemia and showed no other abnormalities. They were diagnosed clinically with DJS. Three novel pathogenic ABCC2 mutations-c.2980delA, c.1834C>T, and c.4465_4473delinsGGCCCACAG-were identified by whole-exome sequencing. These mutations could be responsible for DJS in the two pedigrees. The genetic test confirmed the diagnosis of DJS. Conclusion: These results contributed to the genetic diagnosis of the two patients with DJS and expanded the variant database for the ABCC2 gene.
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Project description:The oral-facial-digital (OFD) syndromes comprise a group of related disorders with a combination of oral, facial and digital anomalies. Variants in several ciliary genes have been associated with subtypes of OFD syndrome, yet in most OFD patients the underlying cause remains unknown. We investigated the molecular basis of disease in two brothers with OFD type II, Mohr syndrome, by performing single-nucleotide polymorphism (SNP)-array analysis on the brothers and their healthy parents to identify homozygous regions and candidate genes. Subsequently, we performed whole-exome sequencing (WES) on the family. Using WES, we identified compound heterozygous variants c.[464G>C];[1226G>A] in NIMA (Never in Mitosis Gene A)-Related Kinase 1 (NEK1). The novel variant c.464G>C disturbs normal splicing in an essential region of the kinase domain. The nonsense variant c.1226G>A, p.(Trp409*), results in nonsense-associated alternative splicing, removing the first coiled-coil domain of NEK1. Candidate variants were confirmed with Sanger sequencing and alternative splicing assessed with cDNA analysis. Immunocytochemistry was used to assess cilia number and length. Patient-derived fibroblasts showed severely reduced ciliation compared with control fibroblasts (18.0 vs 48.9%, P<0.0001), but showed no significant difference in cilia length. In conclusion, we identified compound heterozygous deleterious variants in NEK1 in two brothers with Mohr syndrome. Ciliation in patient fibroblasts is drastically reduced, consistent with a ciliary defect pathogenesis. Our results establish NEK1 variants involved in the etiology of a subset of patients with OFD syndrome type II and support the consideration of including (routine) NEK1 analysis in patients suspected of OFD.
| S-EPMC5117912 | biostudies-literature
Project description:BackgroundDubin-Johnson syndrome (DJS), a rare autosomal recessive liver condition, is caused by biallelic loss-of-function mutations of the ABCC2 gene. This study aimed to investigate genetic variations in the drug efflux transporter ABCC2 (MRP2) gene in patients with DJS and to characterise the expression and mechanism of the ABCC2 gene variant.MethodsTrio whole exome sequencing was performed in the family to identify the genetic causes. Bioinformatics analysis was performed to assess pathogenicity. In in vitro experiments, site-directed mutagenesis was used to introduce ABCC2 variants in constructs then expressed in HEK293T, HuH-7 and HepG2 cell lines. The expression of total and cell membrane MRP2 was quantified in cells expressing the wild-type or variant forms. Chloroquine and MG132 were used to evaluate the effects of p.R393W on lysosomal and/or proteasomal degradation.ResultsThe twin probands carry DJS-associated variants c.1177C>T (rs777902199) in the ABCC2 gene inherited from the father and the c.3632T>C mutation in the other allele inherited from the mother. The ABCC2 variant, c.1177C>T, results in a p.R393W substitution in MRP2 that is highly conserved among vertebrates, drastically decreasing the expression of mutant protein by promoting proteasomal degradation. Another variant c.3632T>C results in a p.L1211P substitution in MRP2, decreasing the expression of membrane MRP2 but not changing the expression of total protein.ConclusionThese results strongly suggest that the p.R393W variant affects the stability of the MRP2 protein and decreases its expression by ubiquitin-mediated proteasomal degradation, and the p.L1211P decreases the expression of membrane MRP2, indicating that these two variants, respectively, cause a loss-of-function of the MRP2 protein and membrane MRP2 ultimately leading to DJS development.
| S-EPMC11770467 | biostudies-literature
Project description:Dubin-Johnson syndrome (DJS) is a rare, autosomal recessive disorder characterized by predominantly conjugated hyperbilirubinemia, caused by a mutation in the adenosine triphosphate-binding cassette subfamily C member 2 (ABCC2) gene coding the multidrug resistance-associated protein 2 (MRP2) protein. ABCC2 mutations have been identified in patients with DJS worldwide; however, the mutation pattern of ABCC2 in China is not well studied. In the present study, the mutation pattern of the ABCC2 gene in Chinese patients with DJS was investigated. A total of 7 clinically confirmed patients with DJS were enrolled, and mutation analysis of the ABCC2 gene was performed by Sanger sequencing of genomic DNA extracted from whole blood. All 32 exons and the adjacent splice junction areas were sequenced. All cases were identified to harbor at least one non-synonymous variant in the ABCC2 gene, including three known mutations in 3 cases and three novel variants (p.G693R, p.G808V and p.E647X) in the other 4 cases, with the known p.R393W and the novel p.G693R and p.E647X variants identified in 2 of the 7 cases (28.6%), respectively. All the identified mutations were heterozygous, and 1 case presented with a compound heterozygous mutation, namely p.G693R/p.G808V, while the other cases carried only one single mutation. The loss of membrane expression of MRP2 caused by the novel nonsense variant, p.E647X, was confirmed by immunohistochemical analysis of liver biopsy. The present study provided the first report on the mutation patterns of the ABCC2 gene in Chinese patients with DJS, and the clinical association of these mutations with the syndrome.
| S-EPMC6176208 | biostudies-literature
Project description:BackgroundPathogenic mutations in EVC or EVC2 gene can lead to Ellis-van Creveld (EvC) syndrome, which is a rare autosomal recessive skeletal dysplasia disorder. This study aimed to determine pathogenic gene variations associated with EvC syndrome in fetuses showing ultrasound anomalies.MethodsA 32-year-old pregnant woman from Quanzhou, China was investigated. In her pregnancy examination, the fetus exhibited multiple fetal malformations, including a narrow thorax, short limbs, postaxial polydactyly, cardiac malformations, and separation of double renal pelvis. Karyotype, chromosomal microarray analysis and whole exome sequencing were performed for prenatal genetic etiology analysis.ResultsChromosome abnormalities and copy number variants were not observed in the fetus using karyotype and chromosomal microarray analysis. Using whole exome sequencing, two compound heterozygous variants NM_147127.5:c.[2484G>A(p.Trp828Ter)];[871-2_894del] in EVC2 gene were identified in the fetus as pathogenic variants inherited from parents.ConclusionsThe study is the first to identify two rare compound variants in EVC2 gene in a Chinese family using whole exome sequencing. The application of whole-exome sequencing would be helpful in fetal etiological diagnosis with ultrasound anomalies.
| S-EPMC10568384 | biostudies-literature
Project description:CEP290 is a ciliary gene frequently mutated in ciliopathies, resulting in a broad range of phenotypes, ranging from isolated inherited retinal disorders (IRDs) to severe or lethal syndromes with multisystemic involvement. Patients with non-syndromic CEP290-linked disease experience profound and early vision loss due to cone-rod dystrophy, as in Leber congenital amaurosis. In this case report, we describe two novel loss-of-function heterozygous alterations in the CEP290 gene, discovered in a patient suffering from retinitis pigmentosa using massive parallel sequencing of a molecular inversion probes library constructed for 108 genes involved in IRDs. A milder phenotype than expected was found in the individual, which serves to prove that some CEP290-associated disorders may display preserved cone function.
| S-EPMC7690422 | biostudies-literature
Project description:BackgroundSensenbrenner syndrome, which is also known as cranioectodermal dysplasia (CED), is a rare, autosomal recessive ciliary chondrodysplasia characterized by a variety of clinical features including a distinctive craniofacial appearance as well as skeletal, ectodermal, liver and renal anomalies. Progressive renal disease can be life-threatening in this condition. CED is a genetically heterogeneous disorder. Currently, variants in any of six genes (IFT122, WDR35, IFT140, IFT43, IFT52 and WDR19) have been associated with this syndrome. All of these genes encode proteins essential for intraflagellar transport (IFT) a process that is required for cilium assembly, maintenance and function. Intra- and interfamilial clinical variability has been reported in CED, which is consistent with CED's genetic heterogeneity and is indicative of genetic background effects.ResultsTwo male CED patients from two unrelated Polish families were included in this study. Clinical assessment revealed distinctive clinical features of Sensenbrenner syndrome, such as dolichocephaly, shortening of long bones and early onset renal failure. Ectodermal anomalies also included thin hair, short and thin nails, and small teeth in both patients. Next generation sequencing (NGS) techniques were performed in order to determine the underlying genetic cause of the disorder using whole exome sequencing (WES) for patient 1 and a custom NGS-based panel for patient 2. Subsequent qPCR and duplex PCR analysis were conducted for both patients. Genetic analyses identified compound heterozygous variants in the IFT140 gene in both affected individuals. Both patients harbored a tandem duplication variant p.Tyr1152_Thr1394dup on one allele. In addition, a novel missense variant, p.(Leu109Pro), and a previously described p.(Gly522Glu) variant were identified in the second allele in patients 1 and 2, respectively. Segregation analysis of the variants was consistent with the expected autosomal recessive disease inheritance pattern. Both patients had severe renal failure requiring kidney transplantation in early childhood.ConclusionThe finding of compound heterozygous IFT140 mutations in two unrelated CED patients provide further evidence that IFT140 gene mutations are associated with this syndrome. Our studies confirm that IFT140 changes in patients with CED are associated with early onset end-stage renal disease. Moreover, this report expands our knowledge of the clinical- and molecular genetics of Sensenbrenner syndrome and it highlights the importance of multidisciplinary approaches in the care of CED patients.
| S-EPMC6995138 | biostudies-literature
Project description:BackgroundEllis-van Creveld syndrome (EvCS) is an autosomal recessive ciliopathy with a disproportionate short stature, polydactyly, dystrophic nails, oral defects, and cardiac anomalies. It is caused by pathogenic variants in the EVC or EVC2 genes. To obtain further insight into the genetics of EvCS, we identified the genetic defect for the EVC2 gene in two Mexican patients.MethodsTwo Mexican families were enrolled in this study. Exome sequencing was applied in the probands to screen potential genetic variant(s), and then Sanger sequencing was used to identify the variant in the parents. Finally, a prediction of the three-dimensional structure of the mutant proteins was made.ResultsOne patient has a compound heterozygous EVC2 mutation: a novel heterozygous variant c.519_519 + 1delinsT inherited from her mother, and a heterozygous variant c.2161delC (p.L721fs) inherited from her father. The second patient has a previously reported compound heterozygous EVC2 mutation: nonsense mutation c.645G > A (p.W215*) in exon 5 inherited from her mother, and c.273dup (p.K92fs) in exon 2 inherited from her father. In both cases, the diagnostic was Ellis-van Creveld syndrome. Three-dimensional modeling of the EVC2 protein showed that truncated proteins are produced in both patients due to the generation of premature stop codons.ConclusionThe identified novel heterozygous EVC2 variants, c.2161delC and c.519_519 + 1delinsT, were responsible for the Ellis-van Creveld syndrome in one of the Mexican patients. In the second Mexican patient, we identified a compound heterozygous variant, c.645G > A and c.273dup, responsible for EvCS. The findings in this study extend the EVC2 mutation spectrum and may provide new insights into the EVC2 causation and diagnosis with implications for genetic counseling and clinical management.
| S-EPMC10137610 | biostudies-literature
Project description:Background: Bernard-Soulier Syndrome (BSS) is a rare autosomal recessive bleeding disorder with large platelets and thrombocytopenia. It is caused by homozygous or compound heterozygous mutations in the GP1BA, GP1BB, or GP9 genes, which together encode the platelet surface receptor glycoprotein complex GPIb-IX-V. Objectives: We report two novel heterozygous mutations in the GP1BA and the GP9 genes, respectively. Patients/Methods: We analyzed the platelet glycoprotein expression by flow cytometry and screened the relevant genes for responsible mutations in two unrelated families. Results: Flow cytometric analyses revealed the absence of CD42a (GPIX) and CD42b (GPIb) on the platelets in the two affected siblings of family 1 and a significantly reduced expression of CD42b (GPIb) in the patient of family 2. In the two siblings, we identified a known frameshift (c.1601_1602delAT) and a novel nonsense mutation (c.1036C>T) in the GP1BA gene that abrogated the production of GP1bα. In the other patient, we found a novel missense mutation (c.112T>C) that was co-inherited with a common one (c.182A>G) in the GP9 gene, respectively. All analyzed heterozygous carriers were asymptomatic and had a normal GPIb-IX-V expression. Conclusions: The two novel GP1BA and GP9 mutations reported herein increment the number of causative genetic defects in BSS.
| S-EPMC7864212 | biostudies-literature
Project description:Joubert syndrome (JBTS) and Meckel-Gruber syndrome (MKS) are rare recessive disorders caused by defects of cilia, and they share overlapping clinical features and allelic loci. Mutations of MKS1 contribute approximately 7% to all MKS cases and are found in some JBTS patients. Here, we describe a JBTS patient with two novel mutations of MKS1. Whole exome sequencing (WES) revealed c.191-1G > A and c.1058delG compound heterozygous variants. The patient presented with typical cerebellar vermis hypoplasia, hypotonia, and developmental delay, but without other renal/hepatic involvement or polydactyly. Functional studies showed that the c.1058delG mutation disrupts the B9 domain of MKS1, attenuates the interactions with B9D2, and impairs its ciliary localization at the transition zone (TZ), indicating that the B9 domain of MKS1 is essential for the integrity of the B9 protein complex and localization of MKS1 at the TZ. This work expands the mutation spectrum of MKS1 and elucidates the clinical heterogeneity of MKS1-related ciliopathies.
| S-EPMC7592398 | biostudies-literature