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‣ Novel splice, missense, and nonsense mutations in the fumarylacetoacetase gene causing tyrosinemia type 1.

Rootwelt, H.; Berger, R.; Gray, G.; Kelly, D. A.; Coşkun, T.; Kvittingen, E. A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1994 Português
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In six unrelated patients with hereditary tyrosinemia type 1 (HT1), three different disease-causing mutations were found by DNA sequencing. Two Pakistani patients, with acute and intermediate forms of HT1, were homozygous for a G192-->T mutation in the last nucleotide of exon 2. This caused aberrant splicing with partial intron 2 retention and premature termination. Three Turkish patients with chronic and intermediate forms of HT1 were homozygous for an A698-->T mutation substituting aspartic acid 233 with valine. A Norwegian patient with an intermediate clinical phenotype was heterozygous for G786-->A, introducing a TGA stop codon for Trp262 (W262X). Site-directed mutagenesis and expression in a rabbit reticulocyte lysate system demonstrated that the nonsense and missense mutations abolished fumarylacetoacetase activity and gave reduced amounts of a truncated and a full-length protein, respectively. Simple tests were established to identify the three mutations by restriction digestion of PCR-amplified genomic DNA. Among 30 additional HT1 patients investigated, 2 were found to be homozygous and 1 heterozygous for G192-->T. Two other patients were homozygous and one was heterozygous for W262X.

‣ Mutations of ESRRB Encoding Estrogen-Related Receptor Beta Cause Autosomal-Recessive Nonsyndromic Hearing Impairment DFNB35

Collin, Rob W.J.; Kalay, Ersan; Tariq, Muhammad; Peters, Theo; van der Zwaag, Bert; Venselaar, Hanka; Oostrik, Jaap; Lee, Kwanghyuk; Ahmed, Zubair M.; Çaylan, Refik; Li, Yun; Spierenburg, Henk A.; Eyupoglu, Erol; Heister, Angelien; Riazuddin, Saima; Baha
Fonte: American Society of Human Genetics Publicador: American Society of Human Genetics
Tipo: Artigo de Revista Científica
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In a large consanguineous family of Turkish origin, genome-wide homozygosity mapping revealed a locus for recessive nonsyndromic hearing impairment on chromosome 14q24.3–q34.12. Fine mapping with microsatellite markers defined the critical linkage interval to a 18.7 cM region flanked by markers D14S53 and D14S1015. This region partially overlapped with the DFNB35 locus. Mutation analysis of ESRRB, a candidate gene in the overlapping region, revealed a homozygous 7 bp duplication in exon 8 in all affected individuals. This duplication results in a frame shift and premature stop codon. Sequence analysis of the ESRRB gene in the affected individuals of the original DFNB35 family and in three other DFNB35-linked consanguineous families from Pakistan revealed four missense mutations. ESRRB encodes the estrogen-related receptor beta protein, and one of the substitutions (p.A110V) is located in the DNA-binding domain of ESRRB, whereas the other three are substitutions (p.L320P, p.V342L, and p.L347P) located within the ligand-binding domain. Molecular modeling of this nuclear receptor showed that the missense mutations are likely to affect the structure and stability of these domains. RNA in situ hybridization in mice revealed that Esrrb is expressed during inner-ear development...

‣ The colR4 and colR15 beta-tubulin mutations in Chlamydomonas reinhardtii confer altered sensitivities to microtubule inhibitors and herbicides by enhancing microtubule stability

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/05/1991 Português
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The colR4 and colR15 beta 2-tubulin missense mutations for lysine-350 in Chlamydomonas reinhardtii (Lee and Huang, 1990) were originally isolated by selection for resistance to the growth inhibitory effects of colchicine. The colR4 and colR15 mutants have been found to be cross resistant to vinblastine and several classes of antimitotic herbicides, including the dinitroanilines (oryzalin, trifluralin, profluralin, and ethafluralin); the phosphoric amide amiprophos methyl; and the dimethyl propynl benzamide pronamide. Like colchicine and vinblastine, the antimitotic effects of these plant-specific herbicides have been associated with the depolymerization of microtubules. In contrast to their resistance to microtubule-depolymerizing drugs, the mutants have an increased sensitivity to taxol, a drug which enhances the polymerization and stability of microtubules. This pattern of altered sensitivity to different microtubule inhibitors was found to cosegregate and corevert with the beta-tubulin mutations providing the first genetic evidence that the in vivo herbicidal effects of the dinitroanilines, amiprophos methyl, and pronamide are related to microtubule function. Although wild-type like in their growth characteristics, the colR4 and colR15 mutants were found to have an altered pattern of microtubules containing acetylated alpha-tubulin...

‣ 250K SNP array karyotyping identifies acquired uniparental disomy and homozygous mutations, including novel missense substitutions of c-Cbl, in myeloid malignancies

Dunbar, Andrew J.; Gondek, Lukasz P.; O’Keefe, Christine L.; Makishima, Hideki; Rataul, Manjot S.; Szpurka, Hadrian; Sekeres, Mikkael A.; Wang, Xiao Fei; McDevitt, Michael A.; Maciejewski, Jaroslaw P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/12/2008 Português
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Two types of acquired loss of heterozygosity are possible in cancer: deletions and copy-neutral uniparental disomy (UPD). Conventionally, copy number losses are identified using metaphase cytogenetics while detection of UPD is accomplished by microsatellite and copy number analysis and as such, is not often used clinically. Recently, introduction of single nucleotide polymorphism (SNP) microarrays have allowed for the systematic and sensitive detection of UPD in hematological malignancies and other cancers. In this study, we have applied 250K SNP array technology to detect previously cryptic chromosomal changes, particularly UPD, in a cohort of 301 patients with myelodysplastic syndromes (MDS), overlap MDS/myeloproliferative disorders (MPD), MPD, and acute myeloid leukemia (AML). We show that UPD is a common chromosomal defect in myeloid malignancies, particularly in chronic myelomonocytic leukemia (CMML; 48%) and MDS/MPD-unclassifiable (38%). Furthermore, we demonstrate that mapping minimally overlapping segmental UPD regions can help target the search for both known and unknown pathogenic mutations, including newly identified missense mutations in the proto-oncogene c-Cbl in 7/12 patients with UPD11q. Acquired mutations of c-Cbl E3 ubiquitin ligase may explain the pathogenesis of a clonal process in a subset of MDS/MPD...

‣ Selective cleavage of AChR cRNAs harbouring mutations underlying the slow channel myasthenic syndrome by hammerhead ribozymes

Abdelgany, Amr; Ealing, John; Wood, Matthew; Beeson, David
Fonte: Library Publishing Media Publicador: Library Publishing Media
Tipo: Artigo de Revista Científica
Publicado em 28/07/2005 Português
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Slow channel congenital myasthenic syndrome (SCCMS) is a dominant disorder caused by missense mutations in muscle acetylcholine receptors (AChR). Expression from mutant alleles causes prolonged AChR ion-channel activations. This ‘gain of function’ results in excitotoxic damage due to excess entry of calcium ions that manifests as an endplate myopathy. The biology of SCCMS provides a model system to investigate the potential of catalytic nucleic acids for therapy in dominantly inherited disorders involving single missense mutations. Hammerhead ribozymes can catalytically cleave RNA transcripts in a sequence-specific manner. We designed hammerhead ribozymes to target transcripts from four SCCMS mutations, αT254I, αS226F, αS269I and εL221F. Ribozymes were incubated with cRNA transcripts encoding wild type and mutant AChR subunits. The ribozymes efficiently cleaved the mutant allele cRNA transcripts but left the wild type cRNA intact. Cleavage efficiency was optimised for αS226F. We were able to demonstrate robust catalytic activity under simulated physiological conditions and at high Ca2+ concentrations, which is likely to be accumulated at the endplate region of the SCCMS patient muscles. These results demonstrate the potential for gene therapy applications of ribozymes to specifically down-regulate expression of mutant alleles in dominantly inherited disorders.

‣ Functional analysis of human mismatch repair gene mutations identifies weak alleles and polymorphisms capable of polygenic interactions

Martinez, Sandra L.; Kolodner, Richard D.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Many of the mutations reported as potentially causing Lynch syndrome are missense mutations in human mismatch repair (MMR) genes. Here, we used a Saccharomyces cerevisiae-based system to study polymorphisms and suspected missense mutations in human MMR genes by modeling them at the appropriate S. cerevisiae chromosomal locus and determining their effect on mutation rates. We identified a number of weak alleles of MMR genes and MMR gene polymorphisms that are capable of interacting with other weak alleles of MMR genes to produce strong polygenic MMR defects. We also identified a number of alleles of MSH2 that act as if they inactivate the Msh2-Msh3 mispair recognition complex thus causing weak MMR defects that interact with an msh6Δ mutation to result in complete MMR defects. These results indicate that weak MMR gene alleles capable of polygenic interactions with other MMR gene alleles may be relatively common.

‣ Novel missense mutation in Charged Multivesicular body Protein 2B in a patient with Frontotemporal Dementia

Ferrari, Raffaele; Kapogiannis, Dimitrios; Huey, Edward D.; Grafman, Jordan; Hardy, John; Momeni, Parastoo
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2010 Português
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Frontotemporal Dementia (FTD) is the second major cause of dementia in persons under the age of 65 after Alzheimer’s disease (AD). FTD is clinically, pathologically and genetically heterogeneous and has been associated with mutations in different genes located on chromosomes 17, 9 and 3. In our study we report a novel heterozygous g.26218G>A variant in exon 6 of Charged Multivesicular body Protein 2B (CHMP2B), predicted to cause the amino acid change p.Ser187Asn, in one patient diagnosed with FTD. We were not able to determine the mode of inheritance of the mutation since we did not have access to the genetically informative family members of the proband; those who were screened did not carry the variant. We didn’t find this variant in 273 Caucasian controls while we did find it in 6 of 94 African American controls. Most of the mutations in CHMP2B which are considered pathogenic lead to partial deletion of the C-terminus region of CHMP2B protein. Based on previous reports and on our current data, missense mutations seem unlikely to be pathogenic. The pathogenicity of CHMP2B mutations requires further investigation.

‣ Loss-of-function germline GATA2 mutations in patients with MDS/AML or MonoMAC syndrome and primary lymphedema reveal a key role for GATA2 in the lymphatic vasculature

Kazenwadel, Jan; Secker, Genevieve A.; Liu, Yajuan J.; Rosenfeld, Jill A.; Wildin, Robert S.; Cuellar-Rodriguez, Jennifer; Hsu, Amy P.; Dyack, Sarah; Fernandez, Conrad V.; Chong, Chan-Eng; Babic, Milena; Bardy, Peter G.; Shimamura, Akiko; Zhang, Michael Y
Fonte: American Society of Hematology Publicador: American Society of Hematology
Tipo: Artigo de Revista Científica
Publicado em 02/02/2012 Português
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Recent work has established that heterozygous germline GATA2 mutations predispose carriers to familial myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML), “MonoMAC” syndrome, and DCML deficiency. Here, we describe a previously unreported MDS family carrying a missense GATA2 mutation (p.Thr354Met), one patient with MDS/AML carrying a frameshift GATA2 mutation (p.Leu332Thrfs*53), another with MDS harboring a GATA2 splice site mutation, and 3 patients exhibiting MDS or MDS/AML who have large deletions encompassing the GATA2 locus. Intriguingly, 2 MDS/AML or “MonoMAC” syndrome patients with GATA2 deletions and one with a frameshift mutation also have primary lymphedema. Primary lymphedema occurs as a result of aberrations in the development and/or function of lymphatic vessels, spurring us to investigate whether GATA2 plays a role in the lymphatic vasculature. We demonstrate here that GATA2 protein is present at high levels in lymphatic vessel valves and that GATA2 controls the expression of genes important for programming lymphatic valve development. Our data expand the phenotypes associated with germline GATA2 mutations to include predisposition to primary lymphedema and suggest that complete haploinsufficiency or loss of function of GATA2...

‣ Mutations of GIPC3 cause nonsyndromic hearing loss DFNB72 but not DFNB81 that also maps to chromosome 19p

Rehman, Atteeq U.; Gul, Khitab; Morell, Robert J.; Lee, Kwanghyuk; Ahmed, Zubair M.; Riazuddin, Saima; Ali, Rana A.; Shahzad, Mohsin; Jaleel, Ateeq-ul; Andrade, Paula B.; Khan, Shaheen N.; Khan, Saadullah; Brewer, Carmen C.; Ahmad, Wasim; Leal, Suzanne M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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A missense mutation of Gipc3 was previously reported to cause age-related hearing loss in mice. Point mutations of human GIPC3 were found in two small families, but association with hearing loss was not statistically significant. Here, we describe one frameshift and six missense mutations in GIPC3 cosegregating with DFNB72 hearing loss in six large families that support statistically significant evidence for genetic linkage. However, GIPC3 is not the only nonsyndromic hearing impairment gene in this region; no GIPC3 mutations were found in a family cosegregating hearing loss with markers of chromosome 19p. Haplotype analysis excluded GIPC3 from the obligate linkage interval in this family and defined a novel locus spanning 4.08 Mb and 104 genes. This closely linked but distinct nonsyndromic hearing loss locus was designated DFNB81.

‣ Exome Sequencing Identifies PDE4D Mutations in Acrodysostosis

Lee, Hane; Graham, John M.; Rimoin, David L.; Lachman, Ralph S.; Krejci, Pavel; Tompson, Stuart W.; Nelson, Stanley F.; Krakow, Deborah; Cohn, Daniel H.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 06/04/2012 Português
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Acrodysostosis is a dominantly-inherited, multisystem disorder characterized by skeletal, endocrine, and neurological abnormalities. To identify the molecular basis of acrodysostosis, we performed exome sequencing on five genetically independent cases. Three different missense mutations in PDE4D, which encodes cyclic AMP (cAMP)-specific phosphodiesterase 4D, were found to be heterozygous in three of the cases. Two of the mutations were demonstrated to have occurred de novo, providing strong genetic evidence of causation. Two additional cases were heterozygous for de novo missense mutations in PRKAR1A, which encodes the cAMP-dependent regulatory subunit of protein kinase A and which has been recently reported to be the cause of a form of acrodysostosis resistant to multiple hormones. These findings demonstrate that acrodysostosis is genetically heterogeneous and underscore the exquisite sensitivity of many tissues to alterations in cAMP homeostasis.

‣ ALDH1A3 Mutations Cause Recessive Anophthalmia and Microphthalmia

Fares-Taie, Lucas; Gerber, Sylvie; Chassaing, Nicolas; Clayton-Smith, Jill; Hanein, Sylvain; Silva, Eduardo; Serey, Margaux; Serre, Valérie; Gérard, Xavier; Baumann, Clarisse; Plessis, Ghislaine; Demeer, Bénédicte; Brétillon, Lionel; Bole, Christine;
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 07/02/2013 Português
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Anophthalmia and microphthalmia (A/M) are early-eye-development anomalies resulting in absent or small ocular globes, respectively. A/M anomalies occur in syndromic or nonsyndromic forms. They are genetically heterogeneous, some mutations in some genes being responsible for both anophthalmia and microphthalmia. Using a combination of homozygosity mapping, exome sequencing, and Sanger sequencing, we identified homozygosity for one splice-site and two missense mutations in the gene encoding the A3 isoform of the aldehyde dehydrogenase 1 (ALDH1A3) in three consanguineous families segregating A/M with occasional orbital cystic, neurological, and cardiac anomalies. ALDH1A3 is a key enzyme in the formation of a retinoic acid gradient along the dorso-ventral axis during early eye development. Transitory expression of mutant ALDH1A3 open reading frames showed that both missense mutations reduce the accumulation of the enzyme, potentially leading to altered retinoic acid synthesis. Although the role of retinoic acid signaling in eye development is well established, our findings provide genetic evidence of a direct link between retinoic-acid-synthesis dysfunction and early-eye-development anomalies in humans.

‣ Yunis-Varón Syndrome Is Caused by Mutations in FIG4, Encoding a Phosphoinositide Phosphatase

Campeau, Philippe M.; Lenk, Guy M.; Lu, James T.; Bae, Yangjin; Burrage, Lindsay; Turnpenny, Peter; Román Corona-Rivera, Jorge; Morandi, Lucia; Mora, Marina; Reutter, Heiko; Vulto-van Silfhout, Anneke T.; Faivre, Laurence; Haan, Eric; Gibbs, Richar
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 02/05/2013 Português
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Yunis-Varón syndrome (YVS) is an autosomal-recessive disorder with cleidocranial dysplasia, digital anomalies, and severe neurological involvement. Enlarged vacuoles are found in neurons, muscle, and cartilage. By whole-exome sequencing, we identified frameshift and missense mutations of FIG4 in affected individuals from three unrelated families. FIG4 encodes a phosphoinositide phosphatase required for regulation of PI(3,5)P2 levels, and thus endosomal trafficking and autophagy. In a functional assay, both missense substitutions failed to correct the vacuolar phenotype of Fig4-null mouse fibroblasts. Homozygous Fig4-null mice exhibit features of YVS, including neurodegeneration and enlarged vacuoles in neurons. We demonstrate that Fig4-null mice also have small skeletons with reduced trabecular bone volume and cortical thickness and that cultured osteoblasts accumulate large vacuoles. Our findings demonstrate that homozygosity or compound heterozygosity for null mutations of FIG4 is responsible for YVS, the most severe known human phenotype caused by defective phosphoinositide metabolism. In contrast, in Charcot-Marie-Tooth disease type 4J (also caused by FIG4 mutations), one of the FIG4 alleles is hypomorphic and disease is limited to the peripheral nervous system. This genotype-phenotype correlation demonstrates that absence of FIG4 activity leads to central nervous system dysfunction and extensive skeletal anomalies. Our results describe a role for PI(3...

‣ An X-Linked Cobalamin Disorder Caused by Mutations in Transcriptional Coregulator HCFC1

Yu, Hung-Chun; Sloan, Jennifer L.; Scharer, Gunter; Brebner, Alison; Quintana, Anita M.; Achilly, Nathan P.; Manoli, Irini; Coughlin, Curtis R.; Geiger, Elizabeth A.; Schneck, Una; Watkins, David; Suormala, Terttu; Van Hove, Johan L.K.; Fowler, Bri
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 05/09/2013 Português
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Derivatives of vitamin B12 (cobalamin) are essential cofactors for enzymes required in intermediary metabolism. Defects in cobalamin metabolism lead to disorders characterized by the accumulation of methylmalonic acid and/or homocysteine in blood and urine. The most common inborn error of cobalamin metabolism, combined methylmalonic acidemia and hyperhomocysteinemia, cblC type, is caused by mutations in MMACHC. However, several individuals with presumed cblC based on cellular and biochemical analysis do not have mutations in MMACHC. We used exome sequencing to identify the genetic basis of an X-linked form of combined methylmalonic acidemia and hyperhomocysteinemia, designated cblX. A missense mutation in a global transcriptional coregulator, HCFC1, was identified in the index case. Additional male subjects were ascertained through two international diagnostic laboratories, and 13/17 had one of five distinct missense mutations affecting three highly conserved amino acids within the HCFC1 kelch domain. A common phenotype of severe neurological symptoms including intractable epilepsy and profound neurocognitive impairment, along with variable biochemical manifestations, was observed in all affected subjects compared to individuals with early-onset cblC. The severe reduction in MMACHC mRNA and protein within subject fibroblast lines suggested a role for HCFC1 in transcriptional regulation of MMACHC...

‣ Mechanotransduction in bone tissue: The A214V and G171V mutations in Lrp5 enhance load-induced osteogenesis in a surface-selective manner☆

Niziolek, Paul J.; Warman, Matthew L.; Robling, Alexander G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Mechanotransduction in bone requires components of the Wnt signaling pathway to produce structurally adapted bone elements. In particular, the Wnt co-receptor LDL-receptor-related protein 5 (LRP5) appears to be a crucial protein in the mechanotransduction cascades that translate physical tissue deformation into new bone formation. Recently discovered missense mutations in LRP5 are associated with high bone mass (HBM), and the altered function of these proteins provide insight into LRP5 function in many skeletal processes, including mechanotransduction. We further investigated the role of LRP5 in bone cell mechanotransduction by applying mechanical stimulation in vivo to two different mutant mouse lines, which harbor HBM-causing missense mutations in Lrp5. Axial tibia loading was applied to mature male Lrp5 G171V and Lrp5 A214V knock-in mice, and to their wild type controls. Fluorochrome labeling revealed that 3 days of loading resulted in a significantly enhanced periosteal response in the A214V knock in mice, whereas the G171V mice exhibited a lowered osteogenic threshold on the endocortical surface. In summary, our data further highlight the importance of Lrp5 in bone cell mechanotransduction, and indicate that the HBM-causing mutations in Lrp5 can alter the anabolic response to mechanical stimulation in favor of increased bone gain.

‣ Rett syndrome mutations abolish the interaction of MeCP2 with the NCoR/SMRT co-repressor

Lyst, Matthew J; Ekiert, Robert; Ebert, Daniel H; Merusi, Cara; Nowak, Jakub; Selfridge, Jim; Guy, Jacky; Kastan, Nathaniel R; Robinson, Nathaniel D; de Lima Alves, Flavia; Rappsilber, Juri; Greenberg, Michael E; Bird, Adrian
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Rett syndrome (RTT) is a severe neurological disorder that is caused by mutations in the MECP2 gene. Many missense mutations causing RTT are clustered in the DNA-binding domain of MeCP2, suggesting that association with chromatin is critical for its function. We identified a second mutational cluster in a previously uncharacterized region of MeCP2. We found that RTT mutations in this region abolished the interaction between MeCP2 and the NCoR/SMRT co-repressor complexes. Mice bearing a common missense RTT mutation in this domain exhibited severe RTT-like phenotypes. Our data are compatible with the hypothesis that brain dysfunction in RTT is caused by a loss of the MeCP2 ‘bridge’ between the NCoR/SMRT co-repressors and chromatin.

‣ Congenital erythrocytosis associated with gain-of-function HIF2A gene mutations and erythropoietin levels in the normal range

Perrotta, Silverio; Stiehl, Daniel P.; Punzo, Francesca; Scianguetta, Saverio; Borriello, Adriana; Bencivenga, Debora; Casale, Maddalena; Nobili, Bruno; Fasoli, Silvia; Balduzzi, Adriana; Cro, Lilla; Nytko, Katarzyna J.; Wenger, Roland H.; Della Ragione,
Fonte: Ferrata Storti Foundation Publicador: Ferrata Storti Foundation
Tipo: Artigo de Revista Científica
Publicado em /10/2013 Português
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Hypoxia-inducible factor 2α (HIF-2α) plays a pivotal role in the balancing of oxygen requirements throughout the body. The protein is a transcription factor that modulates the expression of a wide array of genes and, in turn, controls several key processes including energy metabolism, erythropoiesis and angiogenesis. We describe here the identification of two cases of familial erythrocytosis associated with heterozygous HIF2A missense mutations, namely Ile533Val and Gly537Arg. Ile533Val is a novel mutation and represents the genetic HIF2A change nearest to Pro-531, the primary hydroxyl acceptor residue, so far identified. The Gly537Arg missense mutation has already been described in familial erythrocytosis. However, our patient is the only described case of a de novo HIF2A mutation associated with the development of congenital polycythemia. Functional in vivo studies, based on exogenous expression of hybrid HIF-2α transcription factors, indicated that these genetic alterations lead to the stabilization of HIF-2α protein. All the identified polycythemic subjects with HIF2A mutations show serum erythropoietin in the normal range, independently of the hematocrit values and phlebotomy frequency. The erythroid precursors obtained from the peripheral blood of patients showed an altered phenotype...

‣ Distinct global shifts in genomic binding profiles of limb malformation-associated HOXD13 mutations

Ibrahim, Daniel M.; Hansen, Peter; Rödelsperger, Christian; Stiege, Asita C.; Doelken, Sandra C.; Horn, Denise; Jäger, Marten; Janetzki, Catrin; Krawitz, Peter; Leschik, Gundula; Wagner, Florian; Scheuer, Till; Schmidt-von Kegler, Mareen; Seemann, Petra
Fonte: Cold Spring Harbor Laboratory Press Publicador: Cold Spring Harbor Laboratory Press
Tipo: Artigo de Revista Científica
Publicado em /12/2013 Português
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Gene regulation by transcription factors (TFs) determines developmental programs and cell identity. Consequently, mutations in TFs can lead to dramatic phenotypes in humans by disrupting gene regulation. To date, the molecular mechanisms that actually cause these phenotypes have been difficult to address experimentally. ChIP-seq, which couples chromatin immunoprecipitation with high-throughput sequencing, allows TF function to be investigated on a genome-wide scale, enabling new approaches for the investigation of gene regulation. Here, we present the application of ChIP-seq to explore the effect of missense mutations in TFs on their genome-wide binding profile. Using a retroviral expression system in chicken mesenchymal stem cells, we elucidated the mechanism underlying a novel missense mutation in HOXD13 (Q317K) associated with a complex hand and foot malformation phenotype. The mutated glutamine (Q) is conserved in most homeodomains, a notable exception being bicoid-type homeodomains that have lysine (K) at this position. Our results show that the mutation results in a shift in the binding profile of the mutant toward a bicoid/PITX1 motif. Gene expression analysis and functional assays using in vivo overexpression studies confirm that the mutation results in a partial conversion of HOXD13 into a TF with bicoid/PITX1 properties. A similar shift was not observed with another mutation...

‣ ANGDelMut – a web-based tool for predicting and analyzing functional loss mechanisms of amyotrophic lateral sclerosis-associated angiogenin mutations

Padhi, Aditya K; Vasaikar, Suhas V; Jayaram, Bhyravabhotla; Gomes, James
Fonte: F1000Research Publicador: F1000Research
Tipo: Artigo de Revista Científica
Publicado em 10/02/2014 Português
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ANGDelMut is a web-based tool for predicting the functional consequences of missense mutations in the angiogenin (ANG) protein, which is associated with amyotrophic lateral sclerosis (ALS). Missense mutations in ANG result in loss of either ribonucleolytic activity or nuclear translocation activity or both of these functions, and in turn cause ALS. However, no web-based tools are available to predict whether a newly identified ANG mutation will possibly lead to ALS. More importantly, no web-implemented method is currently available to predict the mechanisms of loss-of-function(s) of ANG mutants. In light of this observation, we developed the ANGDelMut web-based tool, which predicts whether an ANG mutation is deleterious or benign. The user selects certain attributes from the input panel, which serves as a query to infer whether a mutant will exhibit loss of ribonucleolytic activity or nuclear translocation activity or whether the overall stability will be affected. The output states whether the mutation is deleterious or benign, and if it is deleterious, gives the possible mechanism(s) of loss-of-function. This web-based tool, freely available at http://bioschool.iitd.ernet.in/DelMut/, is the first of its kind to provide a platform for researchers and clinicians...

‣ BOR-Syndrome-Associated Eya1 Mutations Lead to Enhanced Proteasomal Degradation of Eya1 Protein

Musharraf, Amna; Kruspe, Dagmar; Tomasch, Jürgen; Besenbeck, Birgit; Englert, Christoph; Landgraf, Kathrin
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 29/01/2014 Português
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Mutations in the human EYA1 gene have been associated with several human diseases including branchio-oto (BO) and branchio-oto-renal (BOR) syndrome, as well as congenital cataracts and ocular anterior segment anomalies. BOR patients suffer from severe malformations of the ears, branchial arches and kidneys. The phenotype of Eya1-heterozygous mice resembles the symptoms of human patients suffering from BOR syndrome. The Eya1 gene encodes a multifunctional protein that acts as a protein tyrosine phosphatase and a transcriptional coactivator. It has been shown that Eya1 interacts with Six transcription factors, which are also required for nuclear translocation of the Eya1 protein. We investigated the effects of seven disease-causing Eya1 missense mutations on Eya1 protein function, in particular cellular localization, ability to interact with Six proteins, and protein stability. We show here that the BOR-associated Eya1 missense mutations S454P, L472R, and L550P lead to enhanced proteasomal degradation of the Eya1 protein in mammalian cells. Moreover, Six proteins lead to a significant stabilization of Eya1, which is caused by Six-mediated protection from proteasomal degradation. In case of the mutant L550P, loss of interaction with Six proteins leads to rapid protein degradation. Our observations suggest that protein destabilization constitutes a novel disease causing mechanism for Eya1.

‣ Disease mutations in the prion-like domains of hnRNPA1 and hnRNPA2/B1 introduce potent steric zippers that drive excess RNP granule assembly

Shorter, James; Taylor, J. Paul
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Publicado em 29/05/2013 Português
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Approximately 1% of human proteins harbor a prion-like domain (PrLD) of similar low complexity sequence and amino acid composition to domains that drive prionogenesis of yeast proteins like Sup35. PrLDs are over-represented in human RNA-binding proteins and mediate phase transitions underpinning RNP granule assembly. This modality renders PrLDs prone to misfold into conformers that accrue in pathological inclusions that characterize various fatal neurodegenerative diseases. For example, TDP-43 and FUS form cytoplasmic inclusions in amyotrophic lateral sclerosis (ALS) and mutations in TDP-43 and FUS can cause ALS. Here, we review our recent discovery of discrete missense mutations that alter a conserved gatekeeper aspartate residue in the PrLDs of hnRNPA2/B1 and hnRNPA1 and cause multisystem proteinopathy and ALS. The missense mutations generate potent steric zippers in the PrLDs, which enhance a natural propensity to form self-templating fibrils, promote recruitment to stress granules and drive cytoplasmic inclusion formation. PrLDs occur in ~250 human proteins and could contribute directly to the etiology of various degenerative disorders.