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‣ Loss of function and inhibitory effects of human CSX/NKX2.5 homeoprotein mutations associated with congenital heart disease

Kasahara, Hideko; Lee, Bora; Schott, Jean-Jacques; Benson, D. Woodrow; Seidman, J.G.; Seidman, Christine E.; Izumo, Seigo
Fonte: American Society for Clinical Investigation Publicador: American Society for Clinical Investigation
Tipo: Artigo de Revista Científica
Publicado em 15/07/2000 Português
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CSX/NKX2.5 is an evolutionarily conserved homeodomain-containing (HD-containing) transcription factor that is essential for early cardiac development. Recently, ten different heterozygous CSX/NKX2.5 mutations were found in patients with congenital heart defects that are transmitted in an autosomal dominant fashion. To determine the consequence of these mutations, we analyzed nuclear localization, DNA binding, transcriptional activation, and dimerization of mutant CSX/NKX2.5 proteins. All mutant proteins were translated and located to the nucleus, except one splice-donor site mutant whose protein did not accumulate in the cell. All mutants that had truncation or missense mutations in the HD had severely reduced DNA binding activity and little or no transcriptional activation function. In contrast, mutants with intact HDs exhibit normal DNA binding to the monomeric binding site but had three- to ninefold reduction in DNA binding to the dimeric binding sites. HD missense mutations that preserved homodimerization ability inhibited the activation of atrial natriuretic factor by wild-type CSX/NKX2.5. Although our studies do not characterize the genotype-phenotype relationship of the ten human mutations, they identify specific abnormalities of CSX/NKX2.5 function essential for transactivation of target genes.

‣ Frequent mutations in the p53 tumor suppressor gene in human leukemia T-cell lines.

Cheng, J; Haas, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1990 Português
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Human T-cell leukemia and T-cell acute lymphoblastic leukemia cell lines were studied for alterations in the p53 tumor suppressor gene. Southern blot analysis of 10 leukemic T-cell lines revealed no gross genomic deletions or rearrangements. Reverse transcription-polymerase chain reaction analysis of p53 mRNA indicated that all 10 lines produced p53 mRNA of normal size. By direct sequencing of polymerase chain reaction-amplified cDNA, we detected 11 missense and nonsense point mutations in 5 of the 10 leukemic T-cell lines studied. The mutations are primarily located in the evolutionarily highly conserved regions of the p53 gene. One of the five cell lines in which a mutation was detected possesses a homozygous point mutation in both p53 alleles, while the other four cell lines harbor from two to four different point mutations. An allelic study of two of the lines (CEM, A3/Kawa) shows that the two missense mutations found in each line are located on separate alleles, thus both alleles of the p53 gene may have been functionally inactivated by two different point mutations. Since cultured leukemic T-cell lines represent a late, fully tumorigenic stage of leukemic T cells, mutation of both (or more) alleles of the p53 gene may reflect the selection of cells possessing an increasingly tumorigenic phenotype...

‣ Clinical implications of hypertrophic cardiomyopathy associated with mutations in the alpha-tropomyosin gene.

Yamauchi-Takihara, K.; Nakajima-Taniguchi, C.; Matsui, H.; Fujio, Y.; Kunisada, K.; Nagata, S.; Kishimoto, T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1996 Português
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OBJECTIVE: The disease-bearing genes for hypertrophic cardiomyopathy (HCM) in HCM families have been identified as the beta-myosin heavy chain, alpha-tropomyosin, and cardiac troponin T genes. Three HCM kindreds with three distinct point mutations in the alpha-tropomyosin gene had extensive clinical evaluations. DESIGN AND RESULTS: Single-strand conformation polymorphism gel analysis of polymerase chain reaction amplified products was used to capture each of the nine exons from the alpha-tropomyosin gene to identify mutations in 60 familial HCM patients. Two missense mutations in exon 2 (Ala63Val and Lys70Thr) and one missense mutation in exon 5 (Asp175Asn) were found in three unrelated HCM kindreds. These kindreds were the subject of clinical, electrocardiographic and echocardiographic studies. The morphological appearance of HCM was similar in the three kindreds. All the patients had severe hypertrophy of the left ventricle with asymmetrical septal hypertrophy during the early stage of the disease, which gradually progressed to dilatation of the left ventricle. Moreover, these kindreds showed similar disease penetrance, age of onset, and incidence of premature sudden death. The disease in these kindreds was severe and resulted in frequent sudden deaths. CONCLUSIONS: Among Japanese patients with familial HCM mutations in the alpha-tropomyosin gene are not as rare as reported...

‣ Novel disease-causing mutations in the dihydropyrimidine dehydrogenase gene interpreted by analysis of the three-dimensional protein structure.

van Kuilenburg, André B P; Dobritzsch, Doreen; Meinsma, Rutger; Haasjes, Janet; Waterham, Hans R; Nowaczyk, Malgorzata J M; Maropoulos, George D; Hein, Guido; Kalhoff, Hermann; Kirk, Jean M; Baaske, Holger; Aukett, Anne; Duley, John A; Ward, Kate P; Lind
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/05/2002 Português
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Dihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disease characterized by thymine-uraciluria in homozygous deficient patients. Cancer patients with a partial deficiency of DPD are at risk of developing severe life-threatening toxicities after the administration of 5-fluorouracil. Thus, identification of novel disease-causing mutations is of the utmost importance to allow screening of patients at risk. In eight patients presenting with a complete DPD deficiency, a considerable variation in the clinical presentation was noted. Whereas motor retardation was observed in all patients, no patients presented with convulsive disorders. In this group of patients, nine novel mutations were identified including one deletion of two nucleotides [1039-1042delTG] and eight missense mutations. Analysis of the crystal structure of pig DPD suggested that five out of eight amino acid exchanges present in these patients with a complete DPD deficiency, Pro86Leu, Ser201Arg, Ser492Leu, Asp949Val and His978Arg, interfered directly or indirectly with cofactor binding or electron transport. Furthermore, the mutations Ile560Ser and Tyr211Cys most likely affected the structural integrity of the DPD protein. Only the effect of the Ile370Val and a previously identified Cys29Arg mutation could not be readily explained by analysis of the three-dimensional structure of the DPD enzyme...

‣ De Novo Mutations in the Sodium-Channel Gene SCN1A Cause Severe Myoclonic Epilepsy of Infancy

Claes, Lieve; Del-Favero, Jurgen; Ceulemans, Berten; Lagae, Lieven; Van Broeckhoven, Christine; De Jonghe, Peter
Fonte: The American Society of Human Genetics Publicador: The American Society of Human Genetics
Tipo: Artigo de Revista Científica
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Severe myoclonic epilepsy of infancy (SMEI) is a rare disorder that occurs in isolated patients. The disease is characterized by generalized tonic, clonic, and tonic-clonic seizures that are initially induced by fever and begin during the first year of life. Later, patients also manifest other seizure types, including absence, myoclonic, andsimple and complex partial seizures. Psychomotor development stagnates around the second year of life. Missense mutations in the gene that codes for a neuronal voltage-gated sodium-channel α-subunit (SCN1A) were identified in families with generalized epilepsy with febrile seizures plus (GEFS+). GEFS+ is a mild type of epilepsy associated with febrile and afebrile seizures. Because both GEFS+ and SMEI involve fever-associated seizures, we screened seven unrelated patients with SMEI for mutations in SCN1A. We identified a mutation in each patient: four had frameshift mutations, one had a nonsense mutation, one had a splice-donor mutation, and one had a missense mutation. All mutations are de novo mutations and were not observed in 184 control chromosomes.

‣ Interaction of nephrocystin-4 and RPGRIP1 is disrupted by nephronophthisis or Leber congenital amaurosis-associated mutations

Roepman, Ronald; Letteboer, Stef J. F.; Arts, Heleen H.; van Beersum, Sylvia E. C.; Lu, Xinrong; Krieger, Elmar; Ferreira, Paulo A.; Cremers, Frans P. M.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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RPGR-interacting protein 1 (RPGRIP1) is a key component of cone and rod photoreceptor cells, where it interacts with RPGR (retinitis pigmentosa GTPase regulator). Mutations in RPGRIP1 lead to autosomal recessive congenital blindness [Leber congenital amaurosis (LCA)]. Most LCA-associated missense mutations in RPGRIP1 are located in a segment that encodes two C2 domains. Based on the C2 domain of novel protein kinase Cε (PKCε), we built a 3D-homology model for the C-terminal C2 domain of RPGRIP1. This model revealed a potential Ca2+-binding site that was predicted to be disrupted by a missense mutation in RPGRIP1, which was previously identified in an LCA patient. Through yeast two-hybrid screening of a retinal cDNA library, we found this C2 domain to specifically bind to nephrocystin-4, encoded by NPHP4. Mutations in NPHP4 are associated with nephronophthisis and a combination of nephronophthisis and retinitis pigmentosa called Senior–Løken syndrome (SLSN). We show that RPGRIP1 and nephrocystin-4 interact strongly in vitro and in vivo, and that they colocalize in the retina, matching the panretinal localization pattern of specific RPGRIP1 isoforms. Their interaction is disrupted by either mutations in RPGRIP1, found in patients with LCA...

‣ ATM mutations and phenotypes in ataxia-telangiectasia families in the British Isles: expression of mutant ATM and the risk of leukemia, lymphoma, and breast cancer.

Stankovic, T; Kidd, A M; Sutcliffe, A; McGuire, G M; Robinson, P; Weber, P; Bedenham, T; Bradwell, A R; Easton, D F; Lennox, G G; Haites, N; Byrd, P J; Taylor, A M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1998 Português
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We report the spectrum of 59 ATM mutations observed in ataxia-telangiectasia (A-T) patients in the British Isles. Of 51 ATM mutations identified in families native to the British Isles, 11 were founder mutations, and 2 of these 11 conferred a milder clinical phenotype with respect to both cerebellar degeneration and cellular features. We report, in two A-T families, an ATM mutation (7271T-->G) that may be associated with an increased risk of breast cancer in both homozygotes and heterozygotes (relative risk 12.7; P=. 0025), although there is a less severe A-T phenotype in terms of the degree of cerebellar degeneration. This mutation (7271T-->G) also allows expression of full-length ATM protein at a level comparable with that in unaffected individuals. In addition, we have studied 18 A-T patients, in 15 families, who developed leukemia, lymphoma, preleukemic T-cell proliferation, or Hodgkin lymphoma, mostly in childhood. A wide variety of ATM mutation types, including missense mutations and in-frame deletions, were seen in these patients. We also show that 25% of all A-T patients carried in-frame deletions or missense mutations, many of which were also associated with expression of mutant ATM protein.

‣ Using Drosophila to Decipher How Mutations Associated With Human Branchio-Oto-Renal Syndrome and Optical Defects Compromise the Protein Tyrosine Phosphatase and Transcriptional Functions of Eyes Absent

Mutsuddi, Mousumi; Chaffee, Benjamin; Cassidy, Justin; Silver, Serena J.; Tootle, Tina L.; Rebay, Ilaria
Fonte: Genetics Society of America Publicador: Genetics Society of America
Tipo: Artigo de Revista Científica
Publicado em /06/2005 Português
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Eyes absent (EYA) proteins are defined by a conserved C-terminal EYA domain (ED) that both contributes to its function as a transcriptional coactivator by mediating protein-protein interactions and possesses intrinsic protein tyrosine phosphatase activity. Mutations in human EYA1 result in an autosomal dominant disorder called branchio-oto-renal (BOR) syndrome as well as congenital cataracts and ocular defects (OD). Both BOR- and OD-associated missense mutations alter residues in the conserved ED as do three missense mutations identified from Drosophila eya alleles. To investigate the molecular mechanisms whereby these mutations disrupt EYA function, we tested their activity in a series of assays that measured in vivo function, phosphatase activity, transcriptional capability, and protein-protein interactions. We find that the OD-associated mutations retain significant in vivo activity whereas those derived from BOR patients show a striking decrease or loss of in vivo functionality. Protein-protein interactions, either with its partner transcription factor Sine oculis or with EYA itself, were not significantly compromised. Finally, the results of the biochemical assays suggest that both loss of protein tyrosine phosphatase activity and reduced transcriptional capability contribute to the impaired EYA function associated with BOR/OD syndrome...

‣ Uromodulin mutations causing familial juvenile hyperuricaemic nephropathy lead to protein maturation defects and retention in the endoplasmic reticulum

Williams, Siân E.; Reed, Anita A.C.; Galvanovskis, Juris; Antignac, Corinne; Goodship, Tim; Karet, Fiona E.; Kotanko, Peter; Lhotta, Karl; Morinière, Vincent; Williams, Paul; Wong, William; Rorsman, Patrik; Thakker, Rajesh V.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Familial juvenile hyperuricaemic nephropathy (FJHN), an autosomal dominant disorder, is caused by mutations in the UMOD gene, which encodes Uromodulin, a glycosylphosphatidylinositol-anchored protein that is expressed in the thick ascending limb of the loop of Henle and excreted in the urine. Uromodulin contains three epidermal growth factor (EGF)-like domains, a cysteine-rich region which includes a domain of eight cysteines and a zona pellucida (ZP) domain. Over 90% of UMOD mutations are missense, and 62% alter a cysteine residue, implicating a role for protein misfolding in the disease. We investigated 20 northern European FJHN probands for UMOD mutations. Wild-type and mutant Uromodulins were functionally studied by expression in HeLa cells and by the use of western blot analysis and confocal microscopy. Six different UMOD missense mutations (Cys32Trp, Arg185Gly, Asp196Asn, Cys217Trp, Cys223Arg and Gly488Arg) were identified. Patients with UMOD mutations were phenotypically similar to those without UMOD mutations. The mutant Uromodulins had significantly delayed maturation, retention in the endoplasmic reticulum (ER) and reduced expression at the plasma membrane. However, Gly488Arg, which is the only mutation we identified in the ZP domain...

‣ Novel SOX2 Mutations and Genotype-Phenotype Correlation in Anophthalmia and Microphthalmia

Schneider, Adele; Bardakjian, Tanya; Reis, Linda M.; Tyler, Rebecca C.; Semina, Elena V.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/2009 Português
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SOX2 represents a High Mobility Group domain containing transcription factor that is essential for normal development in vertebrates. Mutations in SOX2 are known to result in a spectrum of severe ocular phenotypes in humans, also typically associated with other systemic defects. Ocular phenotypes include anophthalmia/microphthalmia (A/M), optic nerve hypoplasia, ocular coloboma and other eye anomalies. We screened 51 unrelated individuals with A/M and indentified SOX2 mutations in the coding region of the gene in 10 individuals. Seven of the identified mutations are novel alterations, while the remaining three individuals carry the previously reported recurrent 20-nucleotide deletion in SOX2, c.70del20. Among the SOX2-positive cases, seven patients had bilateral A/M and mutations resulting in premature termination of the normal protein sequence (7/38; 18% of all bilateral cases), one patient had bilateral A/M associated with a single amino acid insertion (1/38; 3% of bilateral cases), and the final two patients demonstrated unilateral A/M associated with missense mutations (2/13; 15% of all unilateral cases). These findings and review of previously reported cases suggest a potential genotype/phenotype correlation for SOX2 mutations with missense changes generally leading to less severe ocular defects. In addition...

‣ Mutations in p53, p53 protein overexpression and breast cancer survival

Rossner, Pavel; Gammon, Marilie D.; Zhang, Yu-Jing; Terry, Mary Beth; Hibshoosh, Hanina; Memeo, Lorenzo; Mansukhani, Mahesh; Long, Chang-Min; Garbowski, Gail; Agrawal, Meenakshi; Kalra, Tara S.; Gaudet, Mia M.; Teitelbaum, Susan L.; Neugut, Alfred I.; San
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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p53 is an important tumor-suppressor gene that encodes p53 protein, a molecule involved in cell cycle regulation, and has been inconsistently linked to breast cancer survival. Using archived tumor tissue from a population-based sample of 859 women diagnosed with breast cancer between 1996–1997, we determined p53 mutations in exons 5–8 and p53 protein overexpression. We examined the association of p53 mutations with overexpression and selected tumor clinical parameters. We assessed whether either p53 marker was associated with survival through 2002, adjusting for other tumor markers and prognostic factors. The prevalence of protein overexpression in the tumor was 36% (307/859) and any p53 mutation was 15% (128/859). p53 overexpression was positively associated with the presence of any p53 mutation (odds ratio (OR)=2.2, 95% confidence interval (CI)=1.5–3.2), particularly missense mutations (OR=7.0, 95%CI=3.6–13.7). Negative estrogen and progesterone receptor status (ER/PR) was positively associated with both p53 protein overexpression (OR = 2.6, 95% CI = 1.7–4.0), and p53 mutation (OR = 3.9, 95% CI = 2.4–6.5). Any p53 mutation and missense mutations, but not p53 protein overexpression, were associated with breast cancer-specific mortality (Hazard ratio HR=1.7...

‣ Mutations in the Human Laminin β2 (LAMB2) Gene and the Associated Phenotypic Spectrum

Matejas, Verena; Hinkes, Bernward; Alkandari, Faisal; Al-Gazali, Lihadh; Annexstad, Ellen; Aytac, Mehmet B.; Barrow, Margaret; Bláhová, Kvĕta; Bockenhauer, Detlef; Cheong, Hae Il; Maruniak-Chudek, Iwona; Cochat, Pierre; Dötsch, Jörg; Gajjar, Priya; H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/2010 Português
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Mutations of LAMB2 typically cause autosomal recessive Pierson syndrome, a disorder characterized by congenital nephrotic syndrome, ocular and neurologic abnormalities, but may occasionally be associated with milder or oligosymptomatic disease variants. LAMB2 encodes the basement membrane protein laminin β2 which is incorporated in specific heterotrimeric laminin isoforms and has an expression pattern corresponding to the pattern of organ manifestations in Pierson syndrome. Herein we review all previously reported and several novel LAMB2 mutations in relation to the associated phenotype in patients from 39 unrelated families. The majority of disease-causing LAMB2 mutations are truncating, consistent with the hypothesis that loss of laminin β2 function is the molecular basis of Pierson syndrome. While truncating mutations are distributed across the entire gene, missense mutations are clearly clustered in the N-terminal LN domain, which is important for intermolecular interactions. There is an association of missense mutations and small in frame deletions with a higher mean age at onset of renal disease and with absence of neurologic abnormalities, thus suggesting that at least some of these may represent hypomorphic alleles. Nevertheless...

‣ Prioritization of driver mutations in pancreatic cancer using cancer-specific high-throughput annotation of somatic mutations (CHASM)

Carter, Hannah; Samayoa, Josue; Hruban, Ralph H; Karchin, Rachel
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
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Over 20,000 genes were recently sequenced in a series of 24 pancreatic cancers. We applied CHASM (Cancer-specific High-throughput Annotation of Somatic Mutations) to 963 of the missense somatic missense mutations discovered in these 24 cancers. CHASM identified putative driver mutations (false discovery rate ≤0.3) in three known pancreatic cancer driver genes (P53, SMAD4, CDKN2A). An additional 15 genes with putative driver mutations include genes coding for kinases (PIK3CG, DGKA, STK33, TTK and PRKCG), for cell cycle related proteins (NEK8), and for proteins involved in cell adhesion (CMAS, PCDHB2). These and other mutations identified by CHA SM point to potential “driver genes” in pancreatic cancer that should be prioritized for additional follow-up.

‣ Mutations in the Hedgehog Pathway Genes SMO and PTCH1 in Human Gastric Tumors

Wang, Xi-De; Inzunza, Hector; Chang, Han; Qi, Zhenhao; Hu, Beihong; Malone, Daniel; Cogswell, John
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/01/2013 Português
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The causal role of the hedgehog pathway in cancer has been best documented in basal cell carcinoma of the skin. To assess potential DNA alterations of the hedgehog pathway in gastric cancer, we sequenced SMO and PTCH1 genes in a set of 39 gastric tumors. Tumors were classified by histology based on the Lauren classification and Sanger sequencing was performed to obtain full length coding sequences. Genomic instability was evident in these tumors as a number of silent or missense mutations were found. In addition to those that are potential germline polymorphisms, we found three SMO missense mutations, and one PTCH1 frameshift mutation that are novel and have not been documented in basal cell carcinoma. Mutations were found in both intestinal and diffuse type gastric tumors as well as in tumors that exhibit both intestinal and diffuse features. mRNA expression of hedgehog pathway genes was also examined and their levels do not indicate unequivocal higher pathway activity in tumors with mutations than those without. In summary, SMO and/or PTCH1 mutations are present at low frequency in different histologic subtypes of gastric tumors and these do not appear to be driver mutations.

‣ Two novel mutations of the GTP cyclohydrolase 1 gene and genotype–phenotype correlation in Chinese Dopa-responsive dystonia patients

Yu, Lihua; Zhou, Huayong; Hu, Fayun; Xu, Yanming
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
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The most common form of Dopa-responsive dystonia (DRD) is caused by heterozygous mutations in the GTP cyclohydrolase I (GCH1) gene. We screened two unrelated, DRD-symptomatic Chinese Han individuals, for GCH1 gene mutations by direct sequencing. As the clinical manifestations of DRD are highly variable, we also explored the association between genotype and phenotype in all Chinese DRD patients reported so far in the literature, comprising 62 DRD-affected patients from 36 Chinese families. Two novel missense mutations (T94M, L145F) and a novel variant (c. 453+6 G>T) were identified in our two new patients. None of these variants was detected in 200 healthy controls. On the basis of this and other reports, heterozygous mutations were detected in 90.3% of Chinese Han subjects with DRD. Seeming the age of onset for males and females, the mean age was 13 years older in males than in females (P=0.006). Different mutation types did not show any significant differences in age of onset, gender composition, initial symptoms, or the ℒ-dopa dose that abolished the symptoms. Among DRD patients lacking missense or exon–intron boundary mutations, 68.4% were found to possess a large deletion in GCH1, which were detected by multiplex ligation-dependent probe amplification. Most GCH1 mutations were found to cluster in two regions of the coding sequence...

‣ mCSM: predicting the effects of mutations in proteins using graph-based signatures

Pires, Douglas E. V.; Ascher, David B.; Blundell, Tom L.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Motivation: Mutations play fundamental roles in evolution by introducing diversity into genomes. Missense mutations in structural genes may become either selectively advantageous or disadvantageous to the organism by affecting protein stability and/or interfering with interactions between partners. Thus, the ability to predict the impact of mutations on protein stability and interactions is of significant value, particularly in understanding the effects of Mendelian and somatic mutations on the progression of disease. Here, we propose a novel approach to the study of missense mutations, called mCSM, which relies on graph-based signatures. These encode distance patterns between atoms and are used to represent the protein residue environment and to train predictive models. To understand the roles of mutations in disease, we have evaluated their impacts not only on protein stability but also on protein–protein and protein–nucleic acid interactions.

‣ Rare Mutations of CACNB2 Found in Autism Spectrum Disease-Affected Families Alter Calcium Channel Function

Breitenkamp, Alexandra F. S.; Matthes, Jan; Nass, Robert Daniel; Sinzig, Judith; Lehmkuhl, Gerd; Nürnberg, Peter; Herzig, Stefan
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 21/04/2014 Português
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Autism Spectrum Disorders (ASD) are complex neurodevelopmental diseases clinically defined by dysfunction of social interaction. Dysregulation of cellular calcium homeostasis might be involved in ASD pathogenesis, and genes coding for the L-type calcium channel subunits CaV1.2 (CACNA1C) and CaVβ2 (CACNB2) were recently identified as risk loci for psychiatric diseases. Here, we present three rare missense mutations of CACNB2 (G167S, S197F, and F240L) found in ASD-affected families, two of them described here for the first time (G167S and F240L). All these mutations affect highly conserved regions while being absent in a sample of ethnically matched controls. We suggest the mutations to be of physiological relevance since they modulate whole-cell Ba2+ currents through calcium channels when expressed in a recombinant system (HEK-293 cells). Two mutations displayed significantly decelerated time-dependent inactivation as well as increased sensitivity of voltage-dependent inactivation. In contrast, the third mutation (F240L) showed significantly accelerated time-dependent inactivation. By altering the kinetic parameters, the mutations are reminiscent of the CACNA1C mutation causing Timothy Syndrome, a Mendelian disease presenting with ASD. In conclusion...

‣ Truncating and Missense Mutations in IGHMBP2 Cause Charcot-Marie Tooth Disease Type 2

Cottenie, Ellen; Kochanski, Andrzej; Jordanova, Albena; Bansagi, Boglarka; Zimon, Magdalena; Horga, Alejandro; Jaunmuktane, Zane; Saveri, Paola; Rasic, Vedrana Milic; Baets, Jonathan; Bartsakoulia, Marina; Ploski, Rafal; Teterycz, Pawel; Nikolic, Milos;
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 06/11/2014 Português
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Using a combination of exome sequencing and linkage analysis, we investigated an English family with two affected siblings in their 40s with recessive Charcot-Marie Tooth disease type 2 (CMT2). Compound heterozygous mutations in the immunoglobulin-helicase-μ-binding protein 2 (IGHMBP2) gene were identified. Further sequencing revealed a total of 11 CMT2 families with recessively inherited IGHMBP2 gene mutations. IGHMBP2 mutations usually lead to spinal muscular atrophy with respiratory distress type 1 (SMARD1), where most infants die before 1 year of age. The individuals with CMT2 described here, have slowly progressive weakness, wasting and sensory loss, with an axonal neuropathy typical of CMT2, but no significant respiratory compromise. Segregating IGHMBP2 mutations in CMT2 were mainly loss-of-function nonsense in the 5′ region of the gene in combination with a truncating frameshift, missense, or homozygous frameshift mutations in the last exon. Mutations in CMT2 were predicted to be less aggressive as compared to those in SMARD1, and fibroblast and lymphoblast studies indicate that the IGHMBP2 protein levels are significantly higher in CMT2 than SMARD1, but lower than controls, suggesting that the clinical phenotype differences are related to the IGHMBP2 protein levels.

‣ Low Prevalence of CHEK2 Gene Mutations in Multiethnic Cohorts of Breast Cancer Patients in Malaysia

Mohamad, Suriati; Isa, Nurismah Md; Muhammad, Rohaizak; Emran, Nor Aina; Kitan, Nor Mayah; Kang, Peter; Kang, In Nee; Taib, Nur Aishah Mohd; Teo, Soo Hwang; Akmal, Sharifah Noor
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 28/01/2015 Português
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CHEK2 is a protein kinase that is involved in cell-cycle checkpoint control after DNA damage. Germline mutations in CHEK2 gene have been associated with increase in breast cancer risk. The aim of this study is to identify the CHEK2 gene germline mutations among high-risk breast cancer patients and its contribution to the multiethnic population in Malaysia. We screened the entire coding region of CHEK2 gene on 59 high-risk breast cancer patients who tested negative for BRCA1/2 germline mutations from UKM Medical Centre (UKMMC), Hospital Kuala Lumpur (HKL) and Hospital Putrajaya (HPJ). Sequence variants identified were screened further in case-control cohorts consisting of 878 unselected invasive breast cancer patients (180 Malays, 526 Chinese and 172 Indian) and 270 healthy individuals (90 Malays, 90 Chinese and 90 Indian). By screening the entire coding region of the CHEK2 gene, two missense mutations, c.480A>G (p.I160M) and c.538C>T (p.R180C) were identified in two unrelated patients (3.4%). Further screening of these missense mutations on the case-control cohorts unveiled the variant p.I160M in 2/172 (1.1%) Indian cases and 1/90 (1.1%) Indian control, variant p.R180C in 2/526 (0.38%) Chinese cases and 0/90 Chinese control, and in 2/180 (1.1%) of Malay cases and 1/90 (1.1%) of Malay control. The results of this study suggest that CHEK2 mutations are rare among high-risk breast cancer patients and may play a minor contributing role in breast carcinogenesis among Malaysian population.

‣ Analyses of disease-related GNPTAB mutations define a novel GlcNAc-1-phosphotransferase interaction domain and an alternative site-1 protease cleavage site

Velho, Renata Voltolini; De Pace, Raffaella; Klünder, Sarah; Sperb-Ludwig, Fernanda; Lourenço, Charles Marques; Schwartz, Ida V. D.; Braulke, Thomas; Pohl, Sandra
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Mucolipidosis II (MLII) and III alpha/beta are autosomal-recessive diseases of childhood caused by mutations in GNPTAB encoding the α/β-subunit precursor protein of the GlcNAc-1-phosphotransferase complex. This enzyme modifies lysosomal hydrolases with mannose 6-phosphate targeting signals. Upon arrival in the Golgi apparatus, the newly synthesized α/β-subunit precursor is catalytically activated by site-1 protease (S1P). Here we performed comprehensive expression studies of GNPTAB mutations, including two novel mutations T644M and T1223del, identified in Brazilian MLII/MLIII alpha/beta patients. We show that the frameshift E757KfsX1 and the non-sense R587X mutations result in the retention of enzymatically inactive truncated precursor proteins in the endoplasmic reticulum (ER) due to loss of cytosolic ER exit motifs consistent with a severe clinical phenotype in homozygosity. The luminal missense mutations, C505Y, G575R and T644M, partially impaired ER exit and proteolytic activation in accordance with less severe MLIII alpha/beta disease symptoms. Analogous to the previously characterized S399F mutant, we found that the missense mutation I403T led to retention in the ER and loss of catalytic activity. Substitution of further conserved residues in stealth domain 2 (I346 and W357) revealed similar biochemical properties and allowed us to define a putative binding site for accessory proteins required for ER exit of α/β-subunit precursors. Interestingly...