The Experts below are selected from a list of 5022 Experts worldwide ranked by ideXlab platform
Lawrence A Loeb - One of the best experts on this subject based on the ideXlab platform.
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homozygosity for the wrn helicase inactivating variant r834c does not confer a Werner Syndrome clinical phenotype
Scientific Reports, 2017Co-Authors: Ashwini S Kamathloeb, Julia M Sidorova, Raymond J Monnat, Diego Zavalavan G Rankin, Jeny Floresmorales, Mary J Emond, Alessandra Carnevale, Maria Del Carmen Cardenascortes, Thomas H Norwood, Lawrence A LoebAbstract:Loss-of-function mutations in the WRN helicase gene cause Werner Syndrome- a progeroid Syndrome with an elevated risk of cancer and other age-associated diseases. Large numbers of single nucleotide polymorphisms have been identified in WRN. We report here the organismal, cellular, and molecular phenotypes of variant rs3087425 (c. 2500C > T) that results in an arginine to cysteine substitution at residue 834 (R834C) and up to 90% reduction of WRN helicase activity. This variant is present at a high (5%) frequency in Mexico, where we identified 153 heterozygous and three homozygous individuals among 3,130 genotyped subjects. Family studies of probands identified ten additional TT homozygotes. Biochemical analysis of WRN protein purified from TT lymphoblast cell lines confirmed that the R834C substitution strongly and selectively reduces WRN helicase, but not exonuclease activity. Replication track analyses showed reduced replication fork progression in some homozygous cells following DNA replication stress. Among the thirteen TT homozygotes, we identified a previously unreported and statistically significant gender bias in favor of males (p = 0.0016), but none of the clinical findings associated with Werner Syndrome. Our results indicate that WRN helicase activity alone is not rate-limiting for the development of clinical WS.
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the Werner Syndrome exonuclease facilitates dna degradation and high fidelity dna polymerization by human dna polymerase δ
Journal of Biological Chemistry, 2012Co-Authors: Ashwini S Kamathloeb, Jiang-cheng Shen, Michael W Schmitt, Lawrence A LoebAbstract:Abstract DNA Polymerase δ (Pol δ) and the Werner Syndrome (WS) protein, WRN are involved in maintaining cellular genomic stability. Pol δ synthesizes the lagging strand during replication of genomic DNA, and also functions in the synthesis steps of DNA repair and recombination. WRN is a member of the RecQ helicase family, loss of which results in the premature ageing and cancer-prone disorder, Werner Syndrome. Both Pol δ and WRN encode 3′→5′ DNA exonuclease activities. Pol δ exonuclease removes 3′-terminal mismatched nucleotides incorporated during replication to ensure high fidelity DNA synthesis. WRN exonuclease degrades DNA containing alternate secondary structures to prevent formation, and enable resolution of stalled replication forks. We now observe that similarly to WRN, Pol δ degrades alternate DNA structures including bubbles, four-way junctions, and D-loops. Moreover, WRN and Pol δ form a complex with enhanced ability to hydrolyze these structures. We also present evidence that WRN can proof-read for Pol δ; WRN excises 3′-terminal mismatches to enable primer extension by Pol δ. Consistent with our in vitro observations, we show that WRN contributes to the maintenance of DNA synthesis fidelity in vivo. Cells expressing limiting amounts (~10% of normal) of WRN have elevated mutation frequencies compared to wild-type cells. Together, our data highlight the importance of WRN exonuclease activity and its co-operativity with Pol δ in preserving genome stability, which is compromised by the loss of WRN in WS.
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the Werner Syndrome protein is distinguished from the bloom Syndrome protein by its capacity to tightly bind diverse dna structures
PLOS ONE, 2012Co-Authors: Ashwini S Kamathloeb, Lawrence A Loeb, Michael FryAbstract:Loss of Werner Syndrome helicase-exonuclease (WRN) or of its homolog Bloom Syndrome helicase (BLM) results in different inherited disorders. Whereas Werner Syndrome is characterized by premature onset of aging and age-associated diseases, Bloom Syndrome involves developmental abnormalities and increased predisposition to diverse malignancies. To identify biochemical differences between WRN and BLM that might contribute to the dissimilar outcomes of their loss, we compared their abilities to unwind and bind in vitro diverse DNA structures. Full-length recombinant WRN and BLM proteins expressed in and purified from Sf9 insect cells unwound to comparable extents and with similar Km values partial DNA duplex, splayed arm DNA and G'2 bimolecular quadruplex DNA. However, WRN resolved bubble DNA ∼25-fold more efficiently than BLM. The two enzymes were mainly distinguished by their contrasting abilities to bind DNA. WRN bound partial duplexes, bubble and splayed arm DNA and G'2 bimolecular and G4 four-molecular quadruplexes with dissociation constants of 0.25 to 25 nM. By contrast, BLM formed substantial complexes with only G4 quadruplex DNA while binding only marginally other DNA structures. We raise the possibility that in addition to its enzymatic activities WRN may act as a scaffold for the assembly on DNA of additional DNA processing proteins.
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Werner Syndrome gene variants in human sarcomas: Werner Syndrome GENE VARIANTS
Molecular Carcinogenesis, 2009Co-Authors: Jessica J. Hsu, Karen Swisshelm, Ashwini S. Kamath-loeb, Eitan Glick, Brett Wallden, Brian P. Rubin, Lawrence A LoebAbstract:Werner Syndrome is an autosomal inherited disease that is characterized by premature aging. The gene mutated in Werner Syndrome (WS), WRN, encodes both a 3'→5' DNA helicase and a 3'→5' DNA exonuclease. Amongst the WS phenotypes is an exceptionally high incidence of sarcomas. We asked whether spontaneous sarcomas, not known to be associated with WS, also harbor mutations or unreported single nucleotide polymorphisms (SNPs) in WRN. We analyzed RNA or DNA sequences within the helicase and exonuclease domains from 51 and 69 matched sarcoma and adjacent normal tissues, respectively. Among a total of 13 nucleotide polymorphisms detected, we identified three novel non-synonymous polymorphisms: c.611C>T, c.809_810insT, and c.1882C>G. We further characterized one, c.611C>T, which results in substitution of an evolutionarily conserved proline at amino acid 204 in the exonuclease domain with leucine. We show that P204L WRN exhibits a reduction of WRN exonuclease activity; the specific activity is ~10-fold lower than that of wild-type WRN. In contrast, the helicase activity of P204L WRN is reduced less than 2-fold.
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the Werner Syndrome protein binds replication fork and holliday junction dnas as an oligomer
Journal of Biological Chemistry, 2008Co-Authors: Sarah A Compton, Ashwini S Kamathloeb, Lawrence A Loeb, Gokhan Tolun, Jack D GriffithAbstract:Werner Syndrome is an inherited disease displaying a premature aging phenotype. The gene mutated in Werner Syndrome encodes both a 3' --> 5' DNA helicase and a 3' --> 5' DNA exonuclease. Both WRN helicase and exonuclease preferentially utilize DNA substrates containing alternate secondary structures. By virtue of its ability to resolve such DNA structures, WRN is postulated to prevent the stalling and collapse of replication forks that encounter damaged DNA. Using electron microscopy, we visualized the binding of full-length WRN to DNA templates containing replication forks and Holliday junctions, intermediates observed during DNA replication and recombination, respectively. We show that both wild-type WRN and a helicase-defective mutant bind with exceptionally high specificity (>1000-fold) to DNA secondary structures at the replication fork and at Holliday junctions. Little or no binding is observed elsewhere on the DNA molecules. Calculations of the molecular weight of full-length WRN revealed that, in solution, WRN exists predominantly as a dimer. However, WRN bound to DNA is larger; the mass is consistent with that of a tetramer.
Raymond J Monnat - One of the best experts on this subject based on the ideXlab platform.
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homozygosity for the wrn helicase inactivating variant r834c does not confer a Werner Syndrome clinical phenotype
Scientific Reports, 2017Co-Authors: Ashwini S Kamathloeb, Julia M Sidorova, Raymond J Monnat, Diego Zavalavan G Rankin, Jeny Floresmorales, Mary J Emond, Alessandra Carnevale, Maria Del Carmen Cardenascortes, Thomas H Norwood, Lawrence A LoebAbstract:Loss-of-function mutations in the WRN helicase gene cause Werner Syndrome- a progeroid Syndrome with an elevated risk of cancer and other age-associated diseases. Large numbers of single nucleotide polymorphisms have been identified in WRN. We report here the organismal, cellular, and molecular phenotypes of variant rs3087425 (c. 2500C > T) that results in an arginine to cysteine substitution at residue 834 (R834C) and up to 90% reduction of WRN helicase activity. This variant is present at a high (5%) frequency in Mexico, where we identified 153 heterozygous and three homozygous individuals among 3,130 genotyped subjects. Family studies of probands identified ten additional TT homozygotes. Biochemical analysis of WRN protein purified from TT lymphoblast cell lines confirmed that the R834C substitution strongly and selectively reduces WRN helicase, but not exonuclease activity. Replication track analyses showed reduced replication fork progression in some homozygous cells following DNA replication stress. Among the thirteen TT homozygotes, we identified a previously unreported and statistically significant gender bias in favor of males (p = 0.0016), but none of the clinical findings associated with Werner Syndrome. Our results indicate that WRN helicase activity alone is not rate-limiting for the development of clinical WS.
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Werner Syndrome clinical features pathogenesis and potential therapeutic interventions
Ageing Research Reviews, 2017Co-Authors: Junko Oshima, Julia M Sidorova, Raymond J MonnatAbstract:Werner Syndrome (WS) is a prototypical segmental progeroid Syndrome characterized by multiple features consistent with accelerated aging. It is caused by null mutations of the WRN gene, which encodes a member of the RECQ family of DNA helicases. A unique feature of the WRN helicase is the presence of an exonuclease domain in its N-terminal region. Biochemical and cell biological studies during the past decade have demonstrated involvements of the WRN protein in multiple DNA transactions, including DNA repair, recombination, replication and transcription. A role of the WRN protein in telomere maintenance could explain many of the WS phenotypes. Recent discoveries of new progeroid loci found in atypical Werner cases continue to support the concept of genomic instability as a major mechanism of biological aging. Based on these biological insights, efforts are underway to develop therapeutic interventions for WS and related progeroid Syndromes.
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Werner Syndrome through the lens of tissue and tumour genomics
Scientific Reports, 2016Co-Authors: Mari Tokita, Junko Oshima, Scott R. Kennedy, Rosa Ana Risques, Stephen G. Chun, Colin Pritchard, Peter K. Bryant-greenwood, Piri Welcsh, Raymond J MonnatAbstract:Werner Syndrome (WS) is the canonical adult human progeroid (‘premature aging’) Syndrome. Patients with this autosomal recessive Mendelian disorder display constitutional genomic instability and an elevated risk of important age-associated diseases including cancer. Remarkably few analyses of WS patient tissue and tumors have been performed to provide insight into WS disease pathogenesis or the high risk of neoplasia. We used autopsy tissue from four mutation-typed WS patients to characterize pathologic and genomic features of WS, and to determine genomic features of three neoplasms arising in two of these patients. The results of these analyses provide new information on WS pathology and genomics; provide a first genomic characterization of neoplasms arising in WS; and provide new histopathologic and genomic data to test several popular models of WS disease pathogenesis.
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divergent cellular phenotypes of human and mouse cells lacking the Werner Syndrome recq helicase
DNA Repair, 2010Co-Authors: Kiranjit K Dhillon, Julia M Sidorova, Tina M Albertson, Judith B Anderson, Warren C Ladiges, Peter S Rabinovitch, Bradley D Preston, Raymond J MonnatAbstract:Abstract Werner Syndrome (WS) is a human autosomal recessive genetic instability and cancer predisposition Syndrome with features of premature aging. Several genetically determined mouse models of WS have been generated, however, none develops features of premature aging or an elevated risk of neoplasia unless additional genetic perturbations are introduced. In order to determine whether differences in cellular phenotype could explain the discrepant phenotypes of Wrn−/− mice and WRN-deficient humans, we compared the cellular phenotype of newly derived Wrn−/− mouse primary fibroblasts with previous analyses of primary and transformed fibroblasts from WS patients and with newly derived, WRN-depleted human primary fibroblasts. These analyses confirmed previously reported cellular phenotypes of WRN-mutant and WRN-deficient human fibroblasts, and demonstrated that the human WRN-deficient cellular phenotype can be detected in cells grown in 5% or in 20% oxygen. In contrast, we did not identify prominent cellular phenotypes present in WRN-deficient human cells in Wrn−/− mouse fibroblasts. Our results indicate that human and mouse fibroblasts have different functional requirements for WRN protein, and that the absence of a strong cellular phenotype may in part explain the failure of Wrn−/− mice to develop an organismal phenotype resembling Werner Syndrome.
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functional role of the Werner Syndrome recq helicase in human fibroblasts
Aging Cell, 2007Co-Authors: Kiranjit K Dhillon, Yannick Saintigny, Martin Poot, Katherine A Gollahon, Julia M Sidorova, Peter S Rabinovitch, Raymond J MonnatAbstract:Summary Werner Syndrome is an autosomal recessive human genetic instability and cancer predisposition Syndrome that also has features of premature aging. We focused on two questions related to Werner Syndrome protein (WRN) function in human fibroblasts: Do WRN-deficient fibroblasts have a consistent cellular phenotype? What role does WRN play in the recovery from replication arrest? We identified consistent cell proliferation and DNA damage sensitivity defects in both primary and SV40-transformed fibroblasts from different Werner Syndrome patients, and showed that these defects could be revealed by acute depletion of WRN protein. Mechanistic analysis of the role of WRN in recovery from replication arrest indicated that WRN acts to repair damage resulting from replication arrest, rather than to prevent the disruption or breakage of stalled replication forks. These results identify readily quantified cell pheno- types that result from WRN loss in human fibroblasts; delineate the impact of cell transformation on the expres- sion of these phenotypes; and define a mechanistic role for WRN in the recovery from replication arrest.
Vilhelm A Bohr - One of the best experts on this subject based on the ideXlab platform.
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recent advances in understanding Werner Syndrome
F1000Research, 2017Co-Authors: Raghavendra A Shamanna, Deborah L Croteau, Jong Hyuk Lee, Vilhelm A BohrAbstract:Aging, the universal phenomenon, affects human health and is the primary risk factor for major disease pathologies. Progeroid diseases, which mimic aging at an accelerated rate, have provided cues in understanding the hallmarks of aging. Mutations in DNA repair genes as well as in telomerase subunits are known to cause progeroid Syndromes. Werner Syndrome (WS), which is characterized by accelerated aging, is an autosomal-recessive genetic disorder. Hallmarks that define the aging process include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulation of nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. WS recapitulates these hallmarks of aging and shows increased incidence and early onset of specific cancers. Genome integrity and stability ensure the normal functioning of the cell and are mainly guarded by the DNA repair machinery and telomeres. WRN, being a RecQ helicase, protects genome stability by regulating DNA repair pathways and telomeres. Recent advances in WS research have elucidated WRN's role in DNA repair pathway choice regulation, telomere maintenance, resolution of complex DNA structures, epigenetic regulation, and stem cell maintenance.
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Recent Advances in Understanding Werner Syndrome [version 1; referees: 3 approved]
F1000 Research Ltd, 2017Co-Authors: Raghavendra A Shamanna, Deborah L Croteau, Jong Hyuk Lee, Vilhelm A BohrAbstract:Aging, the universal phenomenon, affects human health and is the primary risk factor for major disease pathologies. Progeroid diseases, which mimic aging at an accelerated rate, have provided cues in understanding the hallmarks of aging. Mutations in DNA repair genes as well as in telomerase subunits are known to cause progeroid Syndromes. Werner Syndrome (WS), which is characterized by accelerated aging, is an autosomal-recessive genetic disorder. Hallmarks that define the aging process include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulation of nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. WS recapitulates these hallmarks of aging and shows increased incidence and early onset of specific cancers. Genome integrity and stability ensure the normal functioning of the cell and are mainly guarded by the DNA repair machinery and telomeres. WRN, being a RecQ helicase, protects genome stability by regulating DNA repair pathways and telomeres. Recent advances in WS research have elucidated WRN’s role in DNA repair pathway choice regulation, telomere maintenance, resolution of complex DNA structures, epigenetic regulation, and stem cell maintenance
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active control of repetitive structural transitions between replication forks and holliday junctions by Werner Syndrome helicase
Structure, 2016Co-Authors: Soochul Shin, Vilhelm A Bohr, Jinwoo Lee, Sangwoon Yoo, Tomasz Kulikowicz, Byungchan Ahn, Sungchul HohngAbstract:The reactivation of stalled DNA replication via fork regression invokes Holliday junction formation, branch migration, and the recovery of the replication fork after DNA repair or error-free DNA synthesis. The coordination mechanism for these DNA structural transitions by molecular motors, however, remains unclear. Here we perform single-molecule fluorescence experiments with Werner Syndrome protein (WRN) and model replication forks. The Holliday junction is readily formed once the lagging arm is unwound, and migrated unidirectionally with 3.2 ± 0.03 bases/s velocity. The recovery of the replication fork was controlled by branch migration reversal of WRN, resulting in repetitive fork regression. The Holliday junction formation, branch migration, and migration direction reversal are all ATP dependent, revealing that WRN uses the energy of ATP hydrolysis to actively coordinate the structural transitions of DNA.
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transient overexpression of Werner protein rescues starvation induced autophagy in Werner Syndrome cells
Biochimica et Biophysica Acta, 2014Co-Authors: Jyotirindra Maity, Vilhelm A Bohr, Aparna Laskar, Parimal KarmakarAbstract:Reduced autophagy may be associated with normal and pathological aging. Here we report a link between autophagy and Werner protein (WRNp), mutated in Werner Syndrome, the human premature aging Werner Syndrome (WS). WRN mutant fibroblast AG11395 and AG05229 respond weakly to starvation induced autophagy compared to normal cells. While the fusion of phagosomes with lysosome is normal, WS cells contain fewer autophagy vacuoles. Cellular starvation autophagy in WS cells is restored after transfection with full length WRN. Further, siRNA mediated silencing of WRN in the normal fibroblast cell line WI-38 results in decreased autophagy and altered expression of autophagy related proteins. Thus, our observations suggest that WRN may have a role in controlling autophagy and hereby cellular maintenance.
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roles of Werner Syndrome protein in protection of genome integrity
DNA Repair, 2010Co-Authors: Marie L Rossi, Avik K Ghosh, Vilhelm A BohrAbstract:Werner Syndrome protein (WRN) is one of a family of five human RecQ helicases implicated in the maintenance of genome stability. The conserved RecQ family also includes RecQ1, Bloom Syndrome protein (BLM), RecQ4, and RecQ5 in humans, as well as Sgs1 in Saccharomyces cerevisiae, Rqh1 in Schizosaccharomyces pombe, and homologs in Caenorhabditis elegans, Xenopus laevis, and Drosophila melanogaster. Defects in three of the RecQ helicases, RecQ4, BLM, and WRN, cause human pathologies linked with cancer predisposition and premature aging. Mutations in the WRN gene are the causative factor of Werner Syndrome (WS). WRN is one of the best characterized of the RecQ helicases and is known to have roles in DNA replication and repair, transcription, and telomere maintenance. Studies both in vitro and in vivo indicate that the roles of WRN in a variety of DNA processes are mediated by post-translational modifications, as well as several important protein-protein interactions. In this work, we will summarize some of the early studies on the cellular roles of WRN and highlight the recent findings that shed some light on the link between the protein with its cellular functions and the disease pathology.
Junko Oshima - One of the best experts on this subject based on the ideXlab platform.
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Uncommon cause of cirrhosis—A case of Werner Syndrome with a novel WRN mutation
Indian Journal of Gastroenterology, 2017Co-Authors: S. Deepak Amalnath, Junko Oshima, Forough Sargolzaeiaval, Dipti BaskarAbstract:Werner Syndrome is a rare progeroid Syndrome caused by the WRN gene mutation. It is characterized by a general appearance of premature aging, diabetes mellitus, and atherosclerosis, and an increased risk of malignancies. We report a patient who presented with hematemesis due to cirrhosis of liver and was subsequently diagnosed with Werner Syndrome. Further genetic analysis showed a novel mutation in the WRN gene which has not previously been reported. Werner Syndrome should be considered for the cases of liver cirrhosis when accompanied by the features of accelerated aging.
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accelerated epigenetic aging in Werner Syndrome
Aging (Albany NY), 2017Co-Authors: Anna Maierhofer, Junko Oshima, George M. Martin, Julia Flunkert, Thomas Haaf, Steve HorvathAbstract:Individuals suffering from Werner Syndrome (WS) exhibit many clinical signs of accelerated aging. While the underlying constitutional mutation leads to accelerated rates of DNA damage, it is not yet known whether WS is also associated with an increased epigenetic age according to a DNA methylation based biomarker of aging (the "Epigenetic Clock"). Using whole blood methylation data from 18 WS cases and 18 age matched controls, we find that WS is associated with increased extrinsic epigenetic age acceleration (p=0.0072) and intrinsic epigenetic age acceleration (p=0.04), the latter of which is independent of age-related changes in the composition of peripheral blood cells. A multivariate model analysis reveals that WS is associated with an increase in DNA methylation age (on average 6.4 years, p=0.011) even after adjusting for chronological age, gender, and blood cell counts. Further, WS might be associated with a reduction in naive CD8+ T cells (p=0.025) according to imputed measures of blood cell counts. Overall, this study shows that WS is associated with an increased epigenetic age of blood cells which is independent of changes in blood cell composition. The extent to which this alteration is a cause or effect of WS disease phenotypes remains unknown.
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Werner Syndrome clinical features pathogenesis and potential therapeutic interventions
Ageing Research Reviews, 2017Co-Authors: Junko Oshima, Julia M Sidorova, Raymond J MonnatAbstract:Werner Syndrome (WS) is a prototypical segmental progeroid Syndrome characterized by multiple features consistent with accelerated aging. It is caused by null mutations of the WRN gene, which encodes a member of the RECQ family of DNA helicases. A unique feature of the WRN helicase is the presence of an exonuclease domain in its N-terminal region. Biochemical and cell biological studies during the past decade have demonstrated involvements of the WRN protein in multiple DNA transactions, including DNA repair, recombination, replication and transcription. A role of the WRN protein in telomere maintenance could explain many of the WS phenotypes. Recent discoveries of new progeroid loci found in atypical Werner cases continue to support the concept of genomic instability as a major mechanism of biological aging. Based on these biological insights, efforts are underway to develop therapeutic interventions for WS and related progeroid Syndromes.
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Werner Syndrome through the lens of tissue and tumour genomics
Scientific Reports, 2016Co-Authors: Mari Tokita, Junko Oshima, Scott R. Kennedy, Rosa Ana Risques, Stephen G. Chun, Colin Pritchard, Peter K. Bryant-greenwood, Piri Welcsh, Raymond J MonnatAbstract:Werner Syndrome (WS) is the canonical adult human progeroid (‘premature aging’) Syndrome. Patients with this autosomal recessive Mendelian disorder display constitutional genomic instability and an elevated risk of important age-associated diseases including cancer. Remarkably few analyses of WS patient tissue and tumors have been performed to provide insight into WS disease pathogenesis or the high risk of neoplasia. We used autopsy tissue from four mutation-typed WS patients to characterize pathologic and genomic features of WS, and to determine genomic features of three neoplasms arising in two of these patients. The results of these analyses provide new information on WS pathology and genomics; provide a first genomic characterization of neoplasms arising in WS; and provide new histopathologic and genomic data to test several popular models of WS disease pathogenesis.
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search and insights into novel genetic alterations leading to classical and atypical Werner Syndrome
Gerontology, 2014Co-Authors: Junko Oshima, Fuki M HisamaAbstract:Segmental progeroid Syndromes are a group of disorders with multiple features resembling accelerated aging. Adultonset Werner Syndrome (WS) and childhood-onset Hutchinson-Gilford progeria Syndrome are the best known examples. The discovery of genes responsible for such Syndromes has facilitated our understanding of the basic mechanisms of aging as well as the pathogenesis of other common, agerelated diseases. Our International Registry of Werner Syndrome accesses progeroid pedigrees from all over the world, including those for whom we have ruled out a mutation at the WRN locus. Cases without WRN mutations are operationally categorized as ‘atypical WS’ (AWS). In 2003, we identified LMNA mutations among a subset of AWS cases using a candidate gene approach. As of 2013, the Registry has 142 WS patients with WRN mutations, 11 AWS patients with LMNA mutations, and 49 AWS patients that have neither WRN nor LMNA mutations. Efforts are underway to identify the responsible genes for AWS with unknown genetic causes. While WS and AWS are rare disorders, the causative genes have been shown to have much wider implications for cancer, cardiovascular disease and the biology of aging. Re
Julia M Sidorova - One of the best experts on this subject based on the ideXlab platform.
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homozygosity for the wrn helicase inactivating variant r834c does not confer a Werner Syndrome clinical phenotype
Scientific Reports, 2017Co-Authors: Ashwini S Kamathloeb, Julia M Sidorova, Raymond J Monnat, Diego Zavalavan G Rankin, Jeny Floresmorales, Mary J Emond, Alessandra Carnevale, Maria Del Carmen Cardenascortes, Thomas H Norwood, Lawrence A LoebAbstract:Loss-of-function mutations in the WRN helicase gene cause Werner Syndrome- a progeroid Syndrome with an elevated risk of cancer and other age-associated diseases. Large numbers of single nucleotide polymorphisms have been identified in WRN. We report here the organismal, cellular, and molecular phenotypes of variant rs3087425 (c. 2500C > T) that results in an arginine to cysteine substitution at residue 834 (R834C) and up to 90% reduction of WRN helicase activity. This variant is present at a high (5%) frequency in Mexico, where we identified 153 heterozygous and three homozygous individuals among 3,130 genotyped subjects. Family studies of probands identified ten additional TT homozygotes. Biochemical analysis of WRN protein purified from TT lymphoblast cell lines confirmed that the R834C substitution strongly and selectively reduces WRN helicase, but not exonuclease activity. Replication track analyses showed reduced replication fork progression in some homozygous cells following DNA replication stress. Among the thirteen TT homozygotes, we identified a previously unreported and statistically significant gender bias in favor of males (p = 0.0016), but none of the clinical findings associated with Werner Syndrome. Our results indicate that WRN helicase activity alone is not rate-limiting for the development of clinical WS.
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Werner Syndrome clinical features pathogenesis and potential therapeutic interventions
Ageing Research Reviews, 2017Co-Authors: Junko Oshima, Julia M Sidorova, Raymond J MonnatAbstract:Werner Syndrome (WS) is a prototypical segmental progeroid Syndrome characterized by multiple features consistent with accelerated aging. It is caused by null mutations of the WRN gene, which encodes a member of the RECQ family of DNA helicases. A unique feature of the WRN helicase is the presence of an exonuclease domain in its N-terminal region. Biochemical and cell biological studies during the past decade have demonstrated involvements of the WRN protein in multiple DNA transactions, including DNA repair, recombination, replication and transcription. A role of the WRN protein in telomere maintenance could explain many of the WS phenotypes. Recent discoveries of new progeroid loci found in atypical Werner cases continue to support the concept of genomic instability as a major mechanism of biological aging. Based on these biological insights, efforts are underway to develop therapeutic interventions for WS and related progeroid Syndromes.
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divergent cellular phenotypes of human and mouse cells lacking the Werner Syndrome recq helicase
DNA Repair, 2010Co-Authors: Kiranjit K Dhillon, Julia M Sidorova, Tina M Albertson, Judith B Anderson, Warren C Ladiges, Peter S Rabinovitch, Bradley D Preston, Raymond J MonnatAbstract:Abstract Werner Syndrome (WS) is a human autosomal recessive genetic instability and cancer predisposition Syndrome with features of premature aging. Several genetically determined mouse models of WS have been generated, however, none develops features of premature aging or an elevated risk of neoplasia unless additional genetic perturbations are introduced. In order to determine whether differences in cellular phenotype could explain the discrepant phenotypes of Wrn−/− mice and WRN-deficient humans, we compared the cellular phenotype of newly derived Wrn−/− mouse primary fibroblasts with previous analyses of primary and transformed fibroblasts from WS patients and with newly derived, WRN-depleted human primary fibroblasts. These analyses confirmed previously reported cellular phenotypes of WRN-mutant and WRN-deficient human fibroblasts, and demonstrated that the human WRN-deficient cellular phenotype can be detected in cells grown in 5% or in 20% oxygen. In contrast, we did not identify prominent cellular phenotypes present in WRN-deficient human cells in Wrn−/− mouse fibroblasts. Our results indicate that human and mouse fibroblasts have different functional requirements for WRN protein, and that the absence of a strong cellular phenotype may in part explain the failure of Wrn−/− mice to develop an organismal phenotype resembling Werner Syndrome.
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roles of the Werner Syndrome recq helicase in dna replication
DNA Repair, 2008Co-Authors: Julia M SidorovaAbstract:Congenital deficiency in the WRN protein, a member of the human RecQ helicase family, gives rise to Werner Syndrome, a genetic instability and cancer predisposition disorder with features of premature aging. Cellular roles of WRN are not fully elucidated. WRN has been implicated in telomere maintenance, homologous recombination, DNA repair, and other processes. Here I review the available data that directly address the role of WRN in preserving DNA integrity during replication and propose that WRN can function in coordinating replication fork progression with replication stress-induced fork remodeling. I further discuss this role of WRN within the contexts of damage tolerance group of regulatory pathways, and redundancy and cooperation with other RecQ helicases.
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functional role of the Werner Syndrome recq helicase in human fibroblasts
Aging Cell, 2007Co-Authors: Kiranjit K Dhillon, Yannick Saintigny, Martin Poot, Katherine A Gollahon, Julia M Sidorova, Peter S Rabinovitch, Raymond J MonnatAbstract:Summary Werner Syndrome is an autosomal recessive human genetic instability and cancer predisposition Syndrome that also has features of premature aging. We focused on two questions related to Werner Syndrome protein (WRN) function in human fibroblasts: Do WRN-deficient fibroblasts have a consistent cellular phenotype? What role does WRN play in the recovery from replication arrest? We identified consistent cell proliferation and DNA damage sensitivity defects in both primary and SV40-transformed fibroblasts from different Werner Syndrome patients, and showed that these defects could be revealed by acute depletion of WRN protein. Mechanistic analysis of the role of WRN in recovery from replication arrest indicated that WRN acts to repair damage resulting from replication arrest, rather than to prevent the disruption or breakage of stalled replication forks. These results identify readily quantified cell pheno- types that result from WRN loss in human fibroblasts; delineate the impact of cell transformation on the expres- sion of these phenotypes; and define a mechanistic role for WRN in the recovery from replication arrest.