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‣ Different TBX5 interactions in heart and limb defined by Holt–Oram syndrome mutations

Basson, Craig T.; Huang, Taosheng; Lin, Robert C.; Bachinsky, David R.; Weremowicz, Stanislawa; Vaglio, Alicia; Bruzzone, Rina; Quadrelli, Roberto; Lerone, Margherita; Romeo, Giovanni; Silengo, Margherita; Pereira, Alexandre; Krieger, Jose; Mesquita, Soni
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 16/03/1999 Português
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To better understand the role of TBX5, a T-box containing transcription factor in forelimb and heart development, we have studied the clinical features of Holt–Oram syndrome caused by 10 different TBX5 mutations. Defects predicted to create null alleles caused substantial abnormalities both in limb and heart. In contrast, missense mutations produced distinct phenotypes: Gly80Arg caused significant cardiac malformations but only minor skeletal abnormalities; and Arg237Gln and Arg237Trp caused extensive upper limb malformations but less significant cardiac abnormalities. Amino acids altered by missense mutations were located on the three-dimensional structure of a related T-box transcription factor, Xbra, bound to DNA. Residue 80 is highly conserved within T-box sequences that interact with the major groove of target DNA; residue 237 is located in the T-box domain that selectively binds to the minor groove of DNA. These structural data, taken together with the predominant cardiac or skeletal phenotype produced by each missense mutation, suggest that organ-specific gene activation by TBX5 is predicated on biophysical interactions with different target DNA sequences.

‣ Glucokinase mutations associated with non-insulin-dependent (type 2) diabetes mellitus have decreased enzymatic activity: implications for structure/function relationships.

Gidh-Jain, M; Takeda, J; Xu, L Z; Lange, A J; Vionnet, N; Stoffel, M; Froguel, P; Velho, G; Sun, F; Cohen, D
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/03/1993 Português
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The glycolytic enzyme glucokinase plays an important role in the regulation of insulin secretion and recent studies have shown that mutations in the human glucokinase gene are a common cause of an autosomal dominant form of non-insulin-dependent (type 2) diabetes mellitus (NIDDM) that has an onset often during childhood. The majority of the mutations that have been identified are missense mutations that result in the synthesis of a glucokinase molecule with an altered amino acid sequence. To characterize the effect of these mutations on the catalytic properties of human beta-cell glucokinase, we have expressed native and mutant forms of this protein in Escherichia coli. All of the missense mutations show changes in enzyme activity including a decrease in Vmax and/or increase in Km for glucose. Using a model for the three-dimensional structure of human glucokinase based on the crystal structure of the related enzyme yeast hexokinase B, the mutations map primarily to two regions of the protein. One group of mutations is located in the active site cleft separating the two domains of the enzyme as well as in surface loops leading into this cleft. These mutations usually result in large reductions in enzyme activity. The second group of mutations is located far from the active site in a region that is predicted to undergo a substrate-induced conformational change that results in closure of the active site cleft. These mutations show a small approximately 2-fold reduction in Vmax and a 5- to 10-fold increase in Km for glucose. The characterization of mutations in glucokinase that are associated with a distinct and readily recognizable form of NIDDM has led to the identification of key amino acids involved in glucokinase catalysis and localized functionally important regions of the glucokinase molecule.

‣ Understanding the function–structure and function–mutation relationships of p53 tumor suppressor protein by high-resolution missense mutation analysis

Kato, Shunsuke; Han, Shuang-Yin; Liu, Wen; Otsuka, Kazunori; Shibata, Hiroyuki; Kanamaru, Ryunosuke; Ishioka, Chikashi
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
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Inactivation of the tumor suppressor p53 by missense mutations is the most frequent genetic alteration in human cancers. The common missense mutations in the TP53 gene disrupt the ability of p53 to bind to DNA and consequently to transactivate downstream genes. However, it is still not fully understood how a large number of the remaining mutations affect p53 structure and function. Here, we used a comprehensive site-directed mutagenesis technique and a yeast-based functional assay to construct, express, and evaluate 2,314 p53 mutants representing all possible amino acid substitutions caused by a point mutation throughout the protein (5.9 substitutions per residue), and correlated p53 function with structure- and tumor-derived mutations. This high-resolution mutation analysis allows evaluation of previous predictions and hypotheses through interrelation of function, structure and mutation.

‣ RDS/peripherin gene mutations are frequent causes of central retinal dystrophies.

Kohl, S; Christ-Adler, M; Apfelstedt-Sylla, E; Kellner, U; Eckstein, A; Zrenner, E; Wissinger, B
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1997 Português
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Patients from 76 independent families with various forms of mostly central retinal dystrophies were screened for mutations in the RDS/peripherin gene by means of SSCP analysis and direct DNA sequencing. Two nonsense mutations (Gln239ter, Tyr285ter), five missense mutations (Arg172Trp, Lys197Glu, Gly208Asp, Trp246Arg, Ser289Leu), and one single base insertion (Gly208insG), heterozygous in all cases, were detected. Only one of these mutations, Arg172Trp, has been reported previously. Cosegregation of the mutation with the disease phenotype could be established in selected families. Other missense mutations were excluded from a panel of 55-75 control subjects. The patients showed remarkable variation in phenotype and disease expression not only between cases with different mutations but also between affected members of the same family. This study indicates that RDS/peripherin mutations are a frequent cause of various types of central retinal dystrophies and that the RDS/peripherin gene exhibits a broad spectrum of allelic mutations. Comparative analysis of known mutations allowed us to hypothesise that the deleterious effect of RDS/peripherin gene mutations is the result of different molecular mechanisms.

‣ Mutations in the d-2-Hydroxyglutarate Dehydrogenase Gene Cause d-2-Hydroxyglutaric Aciduria

Struys, Eduard A.; Salomons, Gajja S.; Achouri, Younes; Van Schaftingen, Emile; Grosso, Salvatore; Craigen, William J.; Verhoeven, Nanda M.; Jakobs, Cornelis
Fonte: The American Society of Human Genetics Publicador: The American Society of Human Genetics
Tipo: Artigo de Revista Científica
Português
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d-2-hydroxyglutaric aciduria is a neurometabolic disorder with both a mild and a severe phenotype and with unknown etiology. Recently, a novel enzyme, d-2-hydroxyglutarate dehydrogenase, which converts d-2-hydroxyglutarate into 2-ketoglutarate, and its gene were identified. In the genes of two unrelated patients affected with d-2-hydroxyglutaric aciduria, we identified disease-causing mutations. One patient was homozygous for a missense mutation (c.1331T→C; p.Val444Ala). The other patient was compound heterozygous for a missense mutation (c.440T→G; p.Ile147Ser) and a splice-site mutation (IVS1-23A→G) that resulted in a null allele. Overexpression studies in HEK-293 cells of proteins containing the missense mutations showed a marked reduction of d-2-hydroxyglutarate dehydrogenase activity, proving that mutations in the d-2-hydroxyglutarate dehydrogenase gene cause d-2-hydroxyglutaric aciduria.

‣ The Isolation and Sequence of Missense and Nonsense Mutations in the Cloned Bacteriophage P22 Tailspike Protein Gene

Schwarz, J. J.; Berget, P. B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1989 Português
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Twenty-seven new mutations in the structural gene for the Salmonella typhimurium bacteriophage P22 tailspike protein have been isolated, mapped using a powerful plasmid-based genetic system and their DNA sequence changes determined. The mutations were generated by hydroxylamine treatment of the cloned gene on a plasmid expression vector. Assaying the activity of the tailspike protein produced from this plasmid and screening for plasmid mutants were accomplished by the in situ complementation of P22 capsids imbedded in soft agar to produce infectious phage. Deletion mutations in the cloned gene have been constructed by a two step procedure involving oligonucleotide linker insertion and in vitro deletion by restriction endonuclease digestion. The deletions, whose physical endpoints were determined by DNA sequencing, define 12 genetic and physical intervals into which the new mutations were mapped by marker rescue experiments. These deletions were transferred to phage P22 by recombination and used to map mutations carried on plasmids. Following mapping, the nucleotide change for each of the mutations was determined by DNA sequencing. The majority were absolute missense mutations although both amber and ochre nonsense mutations were also identified in the protein coding portion of the gene. The suppression pattern of the nonsense mutations was determined on several nonsense suppressors. Four of the mutations cause severely depressed levels of tailspike protein expression from both the cloned gene on the plasmid expression vector and from P22 phage carrying these mutations. These mutations were identified as nucleotide changes in what is probably the P22 late operon transcription terminator which immediately follows the tailspike protein coding sequence.

‣ HMG CoA lyase deficiency: identification of five causal point mutations in codons 41 and 42, including a frequent Saudi Arabian mutation, R41Q.

Mitchell, G A; Ozand, P T; Robert, M F; Ashmarina, L; Roberts, J; Gibson, K M; Wanders, R J; Wang, S; Chevalier, I; Plöchl, E; Miziorko, H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1998 Português
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The hereditary deficiency of 3-hydroxy-3-methylglutaryl (HMG) CoA lyase (HL; OMIM 246450 [http://www3.ncbi.nlm.nih. gov:80/htbin-post/Omim/dispmim?246450]) results in episodes of hypoketotic hypoglycemia and coma and is reported to be frequent and clinically severe in Saudi Arabia. We found genetic diversity among nine Saudi HL-deficient probands: six were homozygous for the missense mutation R41Q, and two were homozygous for the frameshift mutation F305fs(-2). In 32 non-Saudi HL-deficient probands, we found three R41Q alleles and also discovered four other deleterious point mutations in codons 41 and 42: R41X, D42E, D42G, and D42H. In purified mutant recombinant HL, all four missense mutations in codons 41 and 42 cause a marked decrease in HL activity. We developed a screening procedure for HL missense mutations that yields residual activity at levels comparable to those obtained using purified HL peptides. Codons 41 and 42 are important for normal HL catalysis and account for a disproportionate 21 (26%) of 82 of mutant alleles in our group of HL-deficient probands.

‣ Molecular basis of iduronate-2-sulphatase gene mutations in patients with mucopolysaccharidosis type II (Hunter syndrome)

Li, P.; Bellows, A.; Thompson, J.
Fonte: BMJ Group Publicador: BMJ Group
Tipo: Artigo de Revista Científica
Publicado em /01/1999 Português
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Mucopolysaccharidosis type II (Hunter syndrome) is an X linked lysosomal storage disorder resulting from heterogeneous mutations in the iduronate-2-sulphatase (IDS) gene. To detect IDS gene mutations, direct sequencing of IDS cDNA fragments coupled with assays on IDS genomic amplicons was applied to 18 unrelated patients with MPS II. Seventeen mutations were detected from the 18 patients including seven missense mutations (S71R, A82E, A85T, R88C, R468W, R468Q, and E521V), five deletions (ΔR95, 383delAT, 596delAACA, 1148delC, and 1216delCT), two insertions (208insC and 1063insA), two splicing mutations (1006+5g→c in intron 7, 1122C→T in exon 8), and an intragenic deletion of IDS exons 4, 5, 6, and 7. Nine of the small mutations were novel mutations. Mutation 596delAACA was detected in two unrelated patients. The mutation in intron 7 was found to cause aberrant splicing and resulted in a 22 bp insertion into its mRNA transcript. The intragenic deleted IDS gene expressed two aberrant mRNA transcripts consisting of exons 1-2-8-9 and 3-8-9. Analysis of mutations A85T, R88C, R468Q, R468W, and 438C/T found no polymorphism for the four missense mutations but about 36% heterozygosity for the 438C/T silent mutation. These results provide further evidence of mutational heterogeneity for MPS II. Also...

‣ Frequent Fas Gene Mutations in Testicular Germ Cell Tumors

Takayama, Hitoshi; Takakuwa, Tetsuya; Tsujimoto, Yuichi; Tani, Yoichi; Nonomura, Norio; Okuyama, Akihiko; Nagata, Shigekazu; Aozasa, Katsuyuki
Fonte: American Society for Investigative Pathology Publicador: American Society for Investigative Pathology
Tipo: Artigo de Revista Científica
Publicado em /08/2002 Português
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The Fas (Apo-1/CD95)/Fas ligand (L) system is involved in cell death signaling, and has been suggested to be important for the regulation of germ cell apoptosis in the testis. Mutations of the Fas gene may result in accumulation of germ cells and thus might contribute to testicular carcinogenesis. The open reading frame of Fas cDNA was examined in 24 cases of testicular germ cell tumors (TGCTs), comprised of 19 pure histological type (15 seminomas, 3 embryonal carcinomas, 1 immature teratoma) and 5 mixed-type tumors. Mutations of the Fas gene were found in nine (37.5%) of these cases. Each lesion with a homogeneous histological picture was selectively microdissected using a laser capture microdissection method: samples consisted of 18 lesions from seminomas, 7 embryonal carcinomas, 4 immature teratomas, 2 choriocarcinomas, and 1 from a yolk sac tumor. Microdissected genomic DNA was examined to determine which mutations were derived from which kind of histological lesion. Eleven mutations were detected in 10 TGCT lesions from nine cases, but none were found in benign lesions. All were point mutations, and eight missense mutations occurred in exon 9 encoding the core protein of the death domain essential for apoptotic signal transduction. Three were silent mutations. Mutations were found in the seminoma (27.8%) and embryonal carcinoma lesions (62.5%)...

‣ Characterization of immune function and analysis of RAG gene mutations in Omenn syndrome and related disorders

Wada, T; Takei, K; Kudo, M; Shimura, S; Kasahara, Y; Koizumi, S; Kawa-Ha, K; Ishida, Y; Imashuku, S; Seki, H; Yachie, A
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em /01/2000 Português
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Omenn syndrome was recently found to be caused by missense mutations in RAG1 or RAG2 gene that result in partial V(D)J recombination activity. Although the clinical hallmarks of the disease are well defined, there have been several cases with clinical findings similar to, but distinct from Omenn syndrome. The data on immune functions and RAG gene mutations of such cases are limited. We described five Japanese infants from four unrelated families, including two cases of Omenn syndrome and three cases of related disorders. Sibling cases with typical Omenn phenotype were found to be compound heterozygotes of R396C and L885R mutations in RAG1. The former has been reported in European cases and may constitute a hot spot. The latter is a novel missense mutation. Infants with related disorders exhibited erythroderma, eosinophilia, hypogammaglobulinaemia, decreased number of B cells and skewing to Th2, and their lymph node specimens showed architectural effacement, lymphocyte depletion and histiocytic hyperplasia, each of which is seen characteristically in Omenn syndrome. However, in these cases serum IgE levels were low or undetectable. We found no mutation in RAG genes except for a K820R substitution in RAG1, which was regarded to be a functional polymorphism...

‣ Rare Missense and Synonymous Variants in UBE1 Are Associated with X-Linked Infantile Spinal Muscular Atrophy

Ramser, Juliane; Ahearn, Mary Ellen; Lenski, Claus; Yariz, Kemal O.; Hellebrand, Heide; von Rhein, Michael; Clark, Robin D.; Schmutzler, Rita K.; Lichtner, Peter; Hoffman, Eric P.; Meindl, Alfons; Baumbach-Reardon, Lisa
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
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X-linked infantile spinal muscular atrophy (XL-SMA) is an X-linked disorder presenting with the clinical features hypotonia, areflexia, and multiple congenital contractures (arthrogryposis) associated with loss of anterior horn cells and infantile death. To identify the XL-SMA disease gene, we performed large-scale mutation analysis in genes located between markers DXS8080 and DXS7132 (Xp11.3–Xq11.1). This resulted in detection of three rare novel variants in exon 15 of UBE1 that segregate with disease: two missense mutations (c.1617 G→T, p.Met539Ile; c.1639 A→G, p.Ser547Gly) present each in one XL-SMA family, and one synonymous C→T substitution (c.1731 C→T, p.Asn577Asn) identified in another three unrelated families. Absence of the missense mutations was demonstrated for 3550 and absence of the synonymous mutation was shown in 7914 control X chromosomes; therefore, these results yielded statistical significant evidence for the association of the synonymous substitution and the two missense mutations with XL-SMA (p = 2.416 × 10−10, p = 0.001815). We also demonstrated that the synonymous C→T substitution leads to significant reduction of UBE1 expression and alters the methylation pattern of exon 15, implying a plausible role of this DNA element in developmental UBE1 expression in humans. Our observations indicate first that XL-SMA is part of a growing list of neurodegenerative disorders associated with defects in the ubiquitin-proteasome pathway and second that synonymous C→T transitions might have the potential to affect gene expression.

‣ Mutations in the GGCX and ABCC6 Genes in a Family with Pseudoxanthoma Elasticum-like Phenotypes

Li, Qiaoli; Grange, Dorothy K.; Armstrong, Nicole L.; Whelan, Alison J.; Hurley, M. Yadira; Rishavy, Mark; Hallgren, Kevin; Berkner, Kathleen L.; Schurgers, Leon J.; Jiang, Qiujie; Uitto, Jouni
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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A characteristic feature of classic PXE, an autosomal recessive disorder caused by mutations in the ABCC6 gene, is aberrant mineralization of connective tissues, particularly the elastic fibers. Here, we report a family with PXE-like cutaneous features in association with multiple coagulation factor deficiency, an autosomal recessive disorder associated with GGCX mutations. The proband and her sister, both with severe skin findings with extensive mineralization, were compound heterozygotes for missense mutations in the GGCX gene, which were shown to result in reduced γ-glutamyl carboxylase activity and in under-carboxylation of matrix gla protein. The proband’s mother and aunt, also manifesting with PXE-like skin changes, were heterozygous carriers of a missense mutation (p.V255M) in GGCX and a null mutation (p.R1141X) in the ABCC6 gene, suggesting digenic nature of their skin findings. Thus, reduced γ-glutamyl carboxylase activity in individuals either compound heterozygous for a missense mutation in GGCX or with haploinsufficiency in GGCX in combination with heterozygosity for ABCC6 gene expression results in aberrant mineralization of skin leading to PXE-like phenotype. These findings expand the molecular basis of PXE-like phenotypes...

‣ Germline Fitness-Based Scoring of Cancer Mutations

Fischer, Andrej; Greenman, Chris; Mustonen, Ville
Fonte: Genetics Society of America Publicador: Genetics Society of America
Tipo: Artigo de Revista Científica
Publicado em /06/2011 Português
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A key goal in cancer research is to find the genomic alterations that underlie malignant cells. Genomics has proved successful in identifying somatic variants at a large scale. However, it has become evident that a typical cancer exhibits a heterogenous mutation pattern across samples. Cases where the same alteration is observed repeatedly seem to be the exception rather than the norm. Thus, pinpointing the key alterations (driver mutations) from a background of variations with no direct causal link to cancer (passenger mutations) is difficult. Here we analyze somatic missense mutations from cancer samples and their healthy tissue counterparts (germline mutations) from the viewpoint of germline fitness. We calibrate a scoring system from protein domain alignments to score mutations and their target loci. We show first that this score predicts to a good degree the rate of polymorphism of the observed germline variation. The scoring is then applied to somatic mutations. We show that candidate cancer genes prone to copy number loss harbor mutations with germline fitness effects that are significantly more deleterious than expected by chance. This suggests that missense mutations play a driving role in tumor suppressor genes. Furthermore...

‣ Identification and functional characterization of rare mutations of the neuroligin-2 gene (NLGN2) associated with schizophrenia

Sun, Chicheng; Cheng, Min-Chih; Qin, Rosie; Liao, Ding-Lieh; Chen, Tzu-Ting; Koong, Farn-Jong; Chen, Gong; Chen, Chia-Hsiang
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Schizophrenia is a severe chronic mental disorder with a high genetic component in its etiology. Several lines of study have suggested that synaptic dysfunction may underlie the pathogenesis of schizophrenia. Neuroligin proteins function as cell-adhesion molecules at post-synaptic membrane and play critical roles in synaptogenesis and synaptic maturation. In this study, we systemically sequenced all the exons and promoter region of neuroligin-2 (NLGN2) gene in a sample of 584 schizophrenia patients and 549 control subjects from Taiwan. In total, we identified 19 genetic variants, including six rare missense mutations such as R215H (one patient), V510M (two patients), R621H (one patient), A637T (two patients), P800L (one patient and one control) and A819S (one patient and one control). In silico analysis predicted that two patient-specific missense mutations, R215H and R621H, had damaging effect, whereas the other missense mutations were benign. Importantly, functional analysis with immunocytochemistry and electrophysiological recordings identified the R215H mutant as a loss-of-function mutant in inducing GABAergic synaptogenesis. Mechanistically, the synaptogenic deficiency of R215H mutant was due to its retention inside the endoplasmic reticulum and inability to be transported to cell membrane. Our study suggests that defects in GABAergic synapse formation in the brain may be an important contributing factor for the onset of schizophrenia. In the family study of this mutation...

‣ Disease-Associated Mutations Disrupt Functionally Important Regions of Intrinsic Protein Disorder

Vacic, Vladimir; Markwick, Phineus R. L.; Oldfield, Christopher J.; Zhao, Xiaoyue; Haynes, Chad; Uversky, Vladimir N.; Iakoucheva, Lilia M.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
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The effects of disease mutations on protein structure and function have been extensively investigated, and many predictors of the functional impact of single amino acid substitutions are publicly available. The majority of these predictors are based on protein structure and evolutionary conservation, following the assumption that disease mutations predominantly affect folded and conserved protein regions. However, the prevalence of the intrinsically disordered proteins (IDPs) and regions (IDRs) in the human proteome together with their lack of fixed structure and low sequence conservation raise a question about the impact of disease mutations in IDRs. Here, we investigate annotated missense disease mutations and show that 21.7% of them are located within such intrinsically disordered regions. We further demonstrate that 20% of disease mutations in IDRs cause local disorder-to-order transitions, which represents a 1.7–2.7 fold increase compared to annotated polymorphisms and neutral evolutionary substitutions, respectively. Secondary structure predictions show elevated rates of transition from helices and strands into loops and vice versa in the disease mutations dataset. Disease disorder-to-order mutations also influence predicted molecular recognition features (MoRFs) more often than the control mutations. The repertoire of disorder-to-order transition mutations is limited...

‣ A classification model for BRCA2 DNA binding domain missense variants based on homology directed repair activity

Guidugli, Lucia; Pankratz, V. Shane; Singh, Namit; Thompson, James; Erding, Catherine A; Engel, Christoph; Schmutzler, Rita; Domchek, Susan; Nathanson, Katherine; Radice, Paolo; Singer, Christian; Tonin, Patricia N.; Lindor, Noralane M.; Goldgar, David E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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The relevance of many BRCA2 variants of uncertain significance (VUS) to breast cancer has not been determined due to limited genetic information from families carrying these alterations. Here we classified six new variants as pathogenic or non-pathogenic by analysis of genetic information from families carrying 65 individual BRCA2 DBD missense mutations using a multifactorial likelihood model of cancer causality. Next, we evaluated the utility of a homology directed DNA break repair (HDR) functional assay as a method for inferring the clinical relevance of VUS in the DNA binding domain (DBD) of BRCA2 using 18 established non-pathogenic missense variants and all 13 established pathogenic missense mutations from the BRCA2 DBD. Compared to the known status of these variants based on the multifactorial likelihood model, the sensitivity of the HDR assay for pathogenic mutations was estimated at 100% (95%CI: 75.3%-100%), and specificity was estimated at 100% (95%CI: 81.5%-100%). A statistical classifier for predicting the probability of pathogenicity of BRCA2 DBD variants was developed using these functional results. When applied to 33 additional VUS, the classifier identified eight with >99% probability of non-pathogenicity and 18 with ≥ 99% probability of pathogenicity. Thus...

‣ Alternating Hemiplegia of Childhood-Related Neural and Behavioural Phenotypes in Na+,K+-ATPase α3 Missense Mutant Mice

Kirshenbaum, Greer S.; Dawson, Neil; Mullins, Jonathan G. L.; Johnston, Tom H.; Drinkhill, Mark J.; Edwards, Ian J.; Fox, Susan H.; Pratt, Judith A.; Brotchie, Jonathan M.; Roder, John C.; Clapcote, Steven J.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 20/03/2013 Português
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Missense mutations in ATP1A3 encoding Na+,K+-ATPase α3 have been identified as the primary cause of alternating hemiplegia of childhood (AHC), a motor disorder with onset typically before the age of 6 months. Affected children tend to be of short stature and can also have epilepsy, ataxia and learning disability. The Na+,K+-ATPase has a well-known role in maintaining electrochemical gradients across cell membranes, but our understanding of how the mutations cause AHC is limited. Myshkin mutant mice carry an amino acid change (I810N) that affects the same position in Na+,K+-ATPase α3 as I810S found in AHC. Using molecular modelling, we show that the Myshkin and AHC mutations display similarly severe structural impacts on Na+,K+-ATPase α3, including upon the K+ pore and predicted K+ binding sites. Behavioural analysis of Myshkin mice revealed phenotypic abnormalities similar to symptoms of AHC, including motor dysfunction and cognitive impairment. 2-DG imaging of Myshkin mice identified compromised thalamocortical functioning that includes a deficit in frontal cortex functioning (hypofrontality), directly mirroring that reported in AHC, along with reduced thalamocortical functional connectivity. Our results thus provide validation for missense mutations in Na+...

‣ BREAST CANCER-ASSOCIATED MISSENSE MUTANTS OF THE PALB2 WD40 DOMAIN, WHICH DIRECTLY BINDS RAD51C, RAD51 AND BRCA2, DISRUPT DNA REPAIR

Park, Jung-Young; Singh, Thiyam R.; Nassar, Nicolas; Zhang, Fan; Freund, Marcel; Hanenberg, Helmut; Meetei, Amom Ruhikanta; Andreassen, Paul R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Heterozygous carriers of germ-line mutations in the BRCA2/FANCD1, PALB2/FANCN, and RAD51C/FANCO DNA repair genes have an increased life-time risk to develop breast, ovarian and other cancers; bi-allelic mutations in these genes clinically manifest as Fanconi anemia (FA). Here, we demonstrate that RAD51C is part of a novel protein complex that contains PALB2 and BRCA2. Further, the PALB2 WD40 domain can directly and independently bind RAD51C and BRCA2. To understand the role of these homologous recombination (HR) proteins in DNA repair, we functionally characterize effects of missense mutations of the PALB2 WD40 domain that have been reported in breast cancer patients. In contrast to large truncations of PALB2, which display a complete loss of interaction, the L939W, T1030I, and L1143P missense mutants/variants of PALB2 WD40 domain are associated with altered direct binding patterns to the RAD51C, RAD51 and BRCA2 HR proteins in biochemical assays. Further, the T1030I missense mutant is unstable, while the L939W and L1143P proteins are stable but partially disrupt the PALB2-RAD51C-BRCA2 complex in cells. Functionally, the L939W and L1143P mutants display a decreased capacity for DNA double-strand break-induced HR and an increased cellular sensitivity to ionizing radiation. As further evidence for the functional importance of the HR complex...

‣ Characterization of a New CDC73 Missense Mutation that Impairs Parafibromin Expression and Nucleolar Localization

Masi, Giulia; Iacobone, Maurizio; Sinigaglia, Alessandro; Mantelli, Barbara; Pennelli, Gianmaria; Castagliuolo, Ignazio; Palù, Giorgio; Barzon, Luisa
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 19/05/2014 Português
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Mutations of the Cell Division Cycle 73 (CDC73) tumor suppressor gene (previously known as HRPT2), encoding for parafibromin, are associated with the Hyperparathyroidism-Jaw Tumor (HPT-JT) syndrome, an autosomal dominant disease whose clinical manifestations are mainly parathyroid tumors and, less frequently, ossifying fibromas of the jaws, uterine and renal tumors. Most mutations of CDC73 are nonsense or frameshift, while missense mutations are rare and generally affect the N-terminal domain of parafibromin, a region that is still poorly characterized. The aim of this study was to characterize a novel somatic CDC73 missense mutation (Ile60Asn) identified in the mandibular tumor of a HPT-JT patient carrying a germline CDC73 inactivating mutation. Immunostaining of the tumor showed reduced nuclear parafibromin immunoreactivity. Western blotting and confocal microscopy of transfected cells demonstrated that the Ile60Asn mutant parafibromin was less expressed than the wild-type protein and exhibited impaired nucleolar localization. Treatment of transfected cells with translation and proteasome inhibitors demonstrated a decreased stability of the Ile60An mutant, partially due to an increase in proteasomal degradation. Overexpression of the Ile60Asn mutant led to increased cell proliferation and to accumulation in the G2/M phase of cell cycle. Moreover...

‣ Hereditary Angioedema Due to C1 Inhibitor Deficiency in Serbia: Two Novel Mutations and Evidence of Genotype-Phenotype Association

Andrejević, Slađana; Korošec, Peter; Šilar, Mira; Košnik, Mitja; Mijanović, Radovan; Bonači-Nikolić, Branka; Rijavec, Matija
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 04/11/2015 Português
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Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare autosomal dominant disease characterized by recurrent life-threatening oedemas and/or abdominal pain and caused by mutations affecting the C1 inhibitor gene, SERPING1. We sought to investigate the spectrum of SERPING1 mutations in Serbia and the possible genotype-phenotype association. C1-INH-HAE was diagnosed on the basis of clinical and laboratory criteria in 40 patients from 27 families; four were asymptomatic. Mutational analysis of the SERPING1 gene was performed by sequencing and multiplex ligation-dependent probe amplification. Disease-causing mutations in SERPING1 were identified in all patients. In C1-INH-HAE type I, we identified 19 different mutations, including 6 missense mutations, 6 nonsense mutations, 2 small deletions, 1 small insertion, 2 splicing defects and 2 large deletions. Two of the mutations (c.300C>T and c.1184_1185insTA) are reported here for the first time. All C1-INH-HAE type II patients from three families harboured the same substitution (c.1396C>T). Based on the type of mutation identified in the SERPING1 gene, patients were divided into two groups: group 1 (nonsense, frameshift, large deletions/insertions, splicing defect, and mutations at Arg444) or group 2 (missense...