scholarly journals Janus-faced EPHB4-associated disorders: novel pathogenic variants and unreported intrafamilial overlapping phenotypes

2021 ◽  
Author(s):  
Silvia Martin-Almedina ◽  
Kazim Ogmen ◽  
Ege Sackey ◽  
Dionysios Grigoriadis ◽  
Christina Karapouliou ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Fetal Hydrops ◽  
Clinical Phenotypes ◽  
Functional Studies ◽  
Pathogenic Variants ◽  
Disease Mechanisms ◽  
Novel Variants ◽  
Uncertain Significance ◽  
Clinical Phenotyping

Abstract Purpose Several clinical phenotypes including fetal hydrops, central conducting lymphatic anomaly or capillary malformations with arteriovenous malformations 2 (CM-AVM2) have been associated with EPHB4 (Ephrin type B receptor 4) variants, demanding new approaches for deciphering pathogenesis of novel variants of uncertain significance (VUS) identified in EPHB4, and for the identification of differentiated disease mechanisms at the molecular level. Methods Ten index cases with various phenotypes, either fetal hydrops, CM-AVM2, or peripheral lower limb lymphedema, whose distinct clinical phenotypes are described in detail in this study, presented with a variant in EPHB4. In vitro functional studies were performed to confirm pathogenicity. Results Pathogenicity was demonstrated for six of the seven novel EPHB4 VUS investigated. A heterogeneity of molecular disease mechanisms was identified, from loss of protein production or aberrant subcellular localization to total reduction of the phosphorylation capability of the receptor. There was some phenotype–genotype correlation; however, previously unreported intrafamilial overlapping phenotypes such as lymphatic-related fetal hydrops (LRFH) and CM-AVM2 in the same family were observed. Conclusion This study highlights the usefulness of protein expression and subcellular localization studies to predict EPHB4 variant pathogenesis. Our accurate clinical phenotyping expands our interpretation of the Janus-faced spectrum of EPHB4-related disorders, introducing the discovery of cases with overlapping phenotypes.

scholarly journals A novel activating JAK1 mutation in chronic eosinophilic leukemia

2021 ◽  
Vol 5 (18) ◽  
pp. 3581-3586 ◽  
Author(s):  
William Shomali ◽  
Alisa Damnernsawad ◽  
Talent Theparee ◽  
David Sampson ◽  
Quinlan Morrow ◽  
...  
Keyword(s):  
World Health ◽  
Variant Of Uncertain Significance ◽  
Jak2 Inhibitor ◽  
Functional Studies ◽  
Chronic Eosinophilic Leukemia ◽  
Uncertain Significance ◽  
Health Organization ◽  
Next Generation Sequencing Ngs ◽  
Stat Pathway

Abstract Hypereosinophilia (HE) has been defined as persistent eosinophilia >1.5 × 109/L; it is broadly divided into primary HE (clonal or neoplastic; HEN), secondary/reactive HE (HER), or HE of undetermined significance (HEUS) when no cause is identified. The use of myeloid next-generation sequencing (NGS) panels has led to the detection of several mutations in patients previously diagnosed with HEUS, reassigning some patients to the category of HEN, specifically the World Health Organization category of chronic eosinophilic leukemia, not otherwise specified (CEL, NOS). Here, we describe a novel somatic JAK1 pseudokinase domain mutation (R629_S632delinsSA) in a patient with HE that had initially been characterized as a variant of uncertain significance. We performed functional studies that demonstrated that this mutation results in growth factor independence of Ba/F3 cells in vitro and activation of the JAK-STAT pathway. These effects were abrogated by the JAK1/JAK2 inhibitor ruxolitinib. R629_S632delinsSA is the first known somatic mutation in JAK1 linked to a clonal eosinophilic neoplasm, and highlights the importance of the JAK-STAT pathway in eosinophil survival.

scholarly journals Functional CDKN2A assay identifies frequent deleterious alleles misclassified as variants of uncertain significance

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Hirokazu Kimura ◽  
Raymond M Paranal ◽  
Neha Nanda ◽  
Laura D Wood ◽  
James R Eshleman ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Ductal Adenocarcinoma ◽  
Proliferation Assay ◽  
Variants Of Uncertain Significance ◽  
Pathogenic Variants ◽  
Deleterious Alleles ◽  
Increased Risk ◽  
Uncertain Significance

Pathogenic germline CDKN2A variants are associated with an increased risk of pancreatic ductal adenocarcinoma (PDAC). CDKN2A variants of uncertain significance (VUSs) are reported in up to 4.3% of patients with PDAC and result in significant uncertainty for patients and their family members as an unknown fraction are functionally deleterious, and therefore, likely pathogenic. Functional characterization of CDKN2A VUSs is needed to reclassify variants and inform clinical management. 29 germline CDKN2A VUSs previously reported in patients with PDAC or in ClinVar were evaluated using a validated in vitro cell proliferation assay. 12 of the 29 CDKN2A VUSs were functionally deleterious (11 VUSs) or potentially functionally deleterious (1 VUS) and were reclassified as likely pathogenic variants. Thus, over 40% of CDKN2A VUSs identified in patients with PDAC are functionally deleterious and likely pathogenic. When incorporating VUSs found to be functionally deleterious, and reclassified as likely pathogenic, the prevalence of pathogenic/likely pathogenic CDKN2A in patients with PDAC reported in the published literature is increased to up to 4.1% of patients, depending on family history. Therefore, CDKN2A VUSs may play a significant, unappreciated role in risk of pancreatic cancer. These findings have significant implications for the counselling and care of patients and their relatives.

scholarly journals Biallelic ERBB3 loss-of-function variants are associated with a novel multisystem syndrome without congenital contracture

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Niu Li ◽  
Yufei Xu ◽  
Yi Zhang ◽  
Guoqiang Li ◽  
Tingting Yu ◽  
...  
Keyword(s):  
Postnatal Growth ◽  
Compound Heterozygous ◽  
Loss Of Function ◽  
Atrioventricular Canal ◽  
Multiple Systems ◽  
Feeding Difficulties ◽  
Functional Studies ◽  
Pathogenic Variants ◽  
Compound Heterozygous Variants

Abstract Background Gain-of-function pathogenic variants of the Erb-B2 receptor tyrosine kinase 3 (ERBB3) gene contribute to the occurrence and development of a variety of human carcinomas through activation of phosphatidylinositol 3-kinase (PI3K)/AKT and extracellular signal-regulated kinase (ERK) signaling. ERBB3 gene homozygous germline variants, whose loss of function may cause autosomal recessive congenital contractural syndrome, were recently identified. This study aims to identify the disease-causing gene in a Chinese pedigree with variable phenotypes involving multiple systems, including developmental delay, postnatal growth retardation, transient lower limb asymmetry, facial malformations, atrioventricular canal malformation, bilateral nystagmus and amblyopia, feeding difficulties, immunodeficiency, anemia, and liver damage, but without congenital contracture. Methods Trio-whole exome sequencing (WES) was performed to identify the disease-causing gene in a 24-month-old Chinese female patient. The pathogenicity of the identified variants was evaluated using in silico tools and in vitro functional studies. Results Trio-WES revealed compound heterozygous variants of c.1253 T > C (p.I418T) and c.3182dupA (p.N1061Kfs*16) in the ERBB3 gene. Functional studies showed that p.I418T resulted in normal expression of ERBB3, which was capable of interacting with ERBB2. However, the variant impaired ERBB3 phosphorylation, consequently blocking ERBB2 phosphorylation and AKT and ERK activation. The truncated protein resulting from the c.3182dupA variant also lacked the capacity to activate downstream signaling pathways. Conclusions We report the first patient with a novel multisystem syndrome disorder without congenital contracture resulting from biallelic loss-of-function variants of ERBB3.

scholarly journals Insights into Genetic Susceptibility to Melanoma by Gene Panel Testing: Potential Pathogenic Variants in ACD, ATM, BAP1, and POT1

Cancers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1007 ◽  
Author(s):  
Lorenza Pastorino ◽  
Virginia Andreotti ◽  
Bruna Dalmasso ◽  
Irene Vanni ◽  
Giulia Ciccarese ◽  
...  
Keyword(s):  
Rare Variants ◽  
Diagnostic Yield ◽  
Susceptibility Genes ◽  
Gene Panel ◽  
Missing Heritability ◽  
Panel Testing ◽  
Pathogenic Variants ◽  
Gene Panel Testing ◽  
Novel Variants ◽  
Uncertain Significance

The contribution of recently established or candidate susceptibility genes to melanoma missing heritability has yet to be determined. Multigene panel testing could increase diagnostic yield and better define the role of candidate genes. We characterized 273 CDKN2A/ARF and CDK4-negative probands through a custom-designed targeted gene panel that included CDKN2A/ARF, CDK4, ACD, BAP1, MITF, POT1, TERF2IP, ATM, and PALB2. Co-segregation, loss of heterozygosity (LOH)/protein expression analysis, and splicing characterization were performed to improve variant classification. We identified 16 (5.9%) pathogenic and likely pathogenic variants in established high/medium penetrance cutaneous melanoma susceptibility genes (BAP1, POT1, ACD, MITF, and TERF2IP), including two novel variants in BAP1 and 4 in POT1. We also found four deleterious and five likely deleterious variants in ATM (3.3%). Thus, including potentially deleterious variants in ATM increased the diagnostic yield to about 9%. Inclusion of rare variants of uncertain significance would increase the overall detection yield to 14%. At least 10% of melanoma missing heritability may be explained through panel testing in our population. To our knowledge, this is the highest frequency of putative ATM deleterious variants reported in melanoma families, suggesting a possible role in melanoma susceptibility, which needs further investigation.

scholarly journals Four Novel Variants in POU4F3 Cause Autosomal Dominant Nonsyndromic Hearing Loss

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Tian-Yi Cui ◽  
Xue Gao ◽  
Sha-Sha Huang ◽  
Yan-Yan Sun ◽  
Si-Qi Zhang ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Autosomal Dominant ◽  
Asian Population ◽  
Nonsyndromic Hearing Loss ◽  
Hereditary Hearing Loss ◽  
Variant Of Uncertain Significance ◽  
Targeted Next Generation Sequencing ◽  
Pathogenic Variants ◽  
Novel Variants ◽  
Uncertain Significance

Hereditary hearing loss is one of the most common sensory disabilities worldwide. Mutation of POU domain class 4 transcription factor 3 (POU4F3) is considered the pathogenic cause of autosomal dominant nonsyndromic hearing loss (ADNSHL), designated as autosomal dominant nonsyndromic deafness 15. In this study, four novel variants in POU4F3, c.696G>T (p.Glu232Asp), c.325C>T (p.His109Tyr), c.635T>C (p.Leu212Pro), and c.183delG (p.Ala62Argfs∗22), were identified in four different Chinese families with ADNSHL by targeted next-generation sequencing and Sanger sequencing. Based on the American College of Medical Genetics and Genomics guidelines, c.183delG (p.Ala62Argfs∗22) is classified as a pathogenic variant, c.696G>T (p.Glu232Asp) and c.635T>C (p.Leu212Pro) are classified as likely pathogenic variants, and c.325C>T (p.His109Tyr) is classified as a variant of uncertain significance. Based on previous reports and the results of this study, we speculated that POU4F3 pathogenic variants are significant contributors to ADNSHL in the East Asian population. Therefore, screening of POU4F3 should be a routine examination for the diagnosis of hereditary hearing loss.

scholarly journals The Steap proteins are metalloreductases

Blood ◽  
2006 ◽  
Vol 108 (4) ◽  
pp. 1388-1394 ◽  
Author(s):  
Robert S. Ohgami ◽  
Dean R. Campagna ◽  
Alice McDonald ◽  
Mark D. Fleming
Keyword(s):  
Subcellular Localization ◽  
Cellular Uptake ◽  
Iron Homeostasis ◽  
Tissue Expression ◽  
Single Electron ◽  
Transmembrane Transport ◽  
Functional Studies ◽  
Electron Reduction

Abstract Iron and copper are essential for all organisms, assuming critical roles as cofactors in many enzymes. In eukaryotes, the transmembrane transport of these elements is a highly regulated process facilitated by the single electron reduction of each metal. Previously, we identified a mammalian ferrireductase, Steap3, critical for erythroid iron homeostasis. Now, through homology, expression, and functional studies, we characterize all 4 members of this protein family and demonstrate that 3 of them, Steap2, Steap3, and Steap4, are not only ferrireductases but also cupric reductases that stimulate cellular uptake of both iron and copper in vitro. Finally, the pattern of tissue expression and subcellular localization of these proteins suggest they are physiologically relevant cupric reductases and ferrireductases in vivo.

scholarly journals An in vivo approach to characterize novel variants associated with musculoskeletal disorders

2021 ◽  
Author(s):  
Aaron N Johnson ◽  
Jennifer McAdow ◽  
Shuo Yang ◽  
Tiffany Ou ◽  
Gary Huang ◽  
...  
Keyword(s):  
Musculoskeletal Disorders ◽  
Fiber Type ◽  
Nemaline Myopathy ◽  
Clinical Severity ◽  
Actin Binding ◽  
Pathogenic Variants ◽  
Novel Variants ◽  
Uncertain Significance ◽  
Transient Overexpression

Pathogenic variants in Tropomyosin 2 (TPM2), which encodes a skeletal muscle specific actin binding protein essential for sarcomere function, cause a spectrum of musculoskeletal disorders including Nemaline Myopathy, Cap Myopathy, congenital fiber type disproportion, and distal arthrogrypsosis (DA). TPM2-related disorders have not been modeled in vivo, so we expressed a series of dominant, pathogenic TPM2 variants in Drosophila embryos and found two variants, K49Del and E122K, disrupted muscle morphogenesis and muscle function. Transient overexpression of K49Del and E122K also disrupted muscle morphogenesis in zebrafish. We further developed a benchmarked overexpression assay in zebrafish to characterize TPM2 variants that we identified in DA patients, and found these variants caused musculoskeletal defects similar to those of the known pathogenic variants. In addition, the severity of musculoskeletal phenotypes in zebrafish expressing TPM2 variants correlated with the severity of clinical phenotypes observed in DA patients. Our study establishes transient overexpression in zebrafish as an efficient platform to characterize variants of uncertain significance in vivo, and argues our assays can predict the clinical severity of musculoskeletal associated variants.

scholarly journals An Overview of the Genetics of ABCA4 Retinopathies, an Evolving Story

Genes ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1241
Author(s):  
Saoud Al-Khuzaei ◽  
Suzanne Broadgate ◽  
Charlotte R. Foster ◽  
Mital Shah ◽  
Jing Yu ◽  
...  
Keyword(s):  
Protein Function ◽  
Phenotypic Variability ◽  
Retinal Dystrophy ◽  
Significant Proportion ◽  
Current Status ◽  
Functional Studies ◽  
Large Gene ◽  
Pathogenic Variants ◽  
Hypomorphic Alleles

Stargardt disease (STGD1) and ABCA4 retinopathies (ABCA4R) are caused by pathogenic variants in the ABCA4 gene inherited in an autosomal recessive manner. The gene encodes an importer flippase protein that prevents the build-up of vitamin A derivatives that are toxic to the RPE. Diagnosing ABCA4R is complex due to its phenotypic variability and the presence of other inherited retinal dystrophy phenocopies. ABCA4 is a large gene, comprising 50 exons; to date >2000 variants have been described. These include missense, nonsense, splicing, structural, and deep intronic variants. Missense variants account for the majority of variants in ABCA4. However, in a significant proportion of patients with an ABCA4R phenotype, a second variant in ABCA4 is not identified. This could be due to the presence of yet unknown variants, or hypomorphic alleles being incorrectly classified as benign, or the possibility that the disease is caused by a variant in another gene. This underlines the importance of accurate genetic testing. The pathogenicity of novel variants can be predicted using in silico programs, but these rely on databases that are not ethnically diverse, thus highlighting the need for studies in differing populations. Functional studies in vitro are useful towards assessing protein function but do not directly measure the flippase activity. Obtaining an accurate molecular diagnosis is becoming increasingly more important as targeted therapeutic options become available; these include pharmacological, gene-based, and cell replacement-based therapies. The aim of this review is to provide an update on the current status of genotyping in ABCA4 and the status of the therapeutic approaches being investigated.

scholarly journals Phenotype and Genotype Study of Chinese POMT2-Related α-Dystroglycanopathy

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiao-Yu Chen ◽  
Dan-Yu Song ◽  
Li Jiang ◽  
Dan-Dan Tan ◽  
Yi-Dan Liu ◽  
...  
Keyword(s):  
Muscular Dystrophy ◽  
Congenital Muscular Dystrophy ◽  
Genetic Characteristics ◽  
Apparent Lack ◽  
Missense Variants ◽  
Novel Variants ◽  
Bioinformatics Software ◽  
Uncertain Significance ◽  
Genetic Features

ObjectiveAlpha-dystroglycanopathy (α-DGP) is a subtype of muscular dystrophy caused by defects in the posttranslational glycosylation of α-dystroglycan (α-DG). Our study aimed to summarize the clinical and genetic features of POMT2-related α-DGP in a cohort of patients in China.MethodsPedigrees, clinical data, and laboratory tests of patients diagnosed with POMT2-related α-DGP were analyzed retrospectively. The pathogenicity of variants in POMT2 were predicted by bioinformatics software. The variants with uncertain significance were verified by further analysis.ResultsThe 11 patients, comprising eight males and three females, were from nine non-consanguineous families. They exhibited different degrees of muscle weakness, ambulation, and intellectual impairment. Among them, three had a muscle-eye-brain disease (MEB)-like phenotype, five presented congenital muscular dystrophy with intellectual disability (CMD-ID), and three presented limb-girdle muscular dystrophy (LGMD). Overall, nine novel variants of POMT2, including two non-sense, one frameshift and six missense variants, were identified. The pathogenicity of two missense variants, c.1891G > C and c.874G > C, was uncertain based on bioinformatics software prediction. In vitro minigene analysis showed that c.1891G > C affects the splicing of POMT2. Immunofluorescence staining with the IIH6C4 antibody of muscle biopsy from the patient carrying the c.874G > C variant showed an apparent lack of expression.ConclusionThis study summarizes the clinical and genetic characteristics of a cohort of POMT2-related α-DGP patients in China for the first time, expanding the mutational spectrum of the disease. Further study of the pathogenicity of some missense variants based on enzyme activity detection is needed.

scholarly journals GFP-Fragment Reassembly Screens for the Functional Characterization of Variants of Uncertain Significance in Protein Interaction Domains of the BRCA1 and BRCA2 Genes

Cancers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 151 ◽  
Author(s):  
Laura Caleca ◽  
Mara Colombo ◽  
Thomas van Overeem Hansen ◽  
Conxi Lázaro ◽  
Siranoush Manoukian ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Functional Characterization ◽  
Brca1 And Brca2 ◽  
Vitro Assay ◽  
Variants Of Uncertain Significance ◽  
Pathogenic Variants ◽  
Brca1 And Brca2 Genes ◽  
Uncertain Significance ◽  
Genome Protection

Genetic testing for BRCA1 and BRCA2 genes has led to the identification of many unique variants of uncertain significance (VUS). Multifactorial likelihood models that predict the odds ratio for VUS in favor or against cancer causality, have been developed, but their use is conditioned by the amount of necessary data, which are difficult to obtain if a variant is rare. As an alternative, variants mapping to the coding regions can be examined using in vitro functional assays. BRCA1 and BRCA2 proteins promote genome protection by interacting with different proteins. In this study, we assessed the functional effect of two sets of variants in BRCA genes by exploiting the green fluorescent protein (GFP)-reassembly in vitro assay, which was set-up to test the BRCA1/BARD1, BRCA1/UbcH5a, and BRCA2/DSS1 interactions. Based on the findings observed for the validation panels of previously classified variants, BRCA1/UbcH5a and BRCA2/DSS1 binding assays showed 100% sensitivity and specificity in identifying pathogenic and non-pathogenic variants. While the actual efficiency of these assays in assessing the clinical significance of BRCA VUS has to be verified using larger validation panels, our results suggest that the GFP-reassembly assay is a robust method to identify variants affecting normal protein functioning and contributes to the classification of VUS.

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