Philip Mason - Academia.edu (original) (raw)
Papers by Philip Mason
Annals of Medicine, Jun 3, 2014
The inherited bone marrow failure syndromes are a diverse group of genetic diseases associated wi... more The inherited bone marrow failure syndromes are a diverse group of genetic diseases associated with inadequate production of one or more blood cell lineages. Examples include Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan anemia, thrombocytopenia absent radii syndrome, severe congenital neutropenia, and Shwachman-Diamond syndrome. The management of these disorders was once the exclusive domain of pediatric subspecialists, but increasingly physicians who care for adults are being called upon to diagnose or treat these conditions. Through a series of patient vignettes, we highlight the clinical manifestations of inherited bone marrow failure syndromes in adolescents and young adults. The diagnostic and therapeutic challenges posed by these diseases are discussed.
Acta Crystallographica Section D-biological Crystallography, Apr 1, 1999
Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structur... more Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structure solved by molecular replacement. Crystals of the natural mutant R459L grow under similar conditions in space groups P2 1 2 1 2 1 and C222 1 with eight or four 515-residue molecules in the asymmetric unit, respectively. A non-crystallographic 222 tetramer was found in the C222 1 crystal form using a 4 A Ê resolution data set and a dimer of the large + domains of the Leuconostoc mesenteroides enzyme as a search model. This tetramer was the only successful search model for the P2 1 2 1 2 1 crystal form using data to 3 A Ê. Crystals of the deletion mutant ÁG6PD grow in space group F222 with a monomer in the asymmetric unit; 2.5 A Ê resolution data have been collected. Comparison of the packing of tetramers in the three space groups suggests that the N-terminal tail of the enzyme prevents crystallization with exact 222 molecular symmetry.
F1000 - Post-publication peer review of the biomedical literature, 2016
Small-molecule antagonists disable discrete biochemical properties of protein targets. For multid... more Small-molecule antagonists disable discrete biochemical properties of protein targets. For multidomain protein targets, the pharmacologic consequence of drug action is limited by selective disruption of one domain-specific activity. More broadly, target inhibition is kinetically limited by the durability and degree of target engagement. These features of traditional drug molecules are challenging to the development of inhibitors targeting transcription factors and chromatinassociated epigenetic proteins, which function as multi-domain biomolecular scaffolds and generally feature rapid association and dissociation kinetics. We therefore devised a chemical strategy to prompt ligand-dependent target protein degradation, via chemical conjugation with derivatized phthalimides that hijack the function of the Cereblon E3 ubiquitin ligase complex. Using this approach, we converted an acetyl-lysine competitive antagonist that displaces BET bromodomains from chromatin (JQ1) to a phthalimide-conjugated ligand that prompts immediate Cereblon-dependent BET protein degradation (dBET1). Expression proteomics confirms high specificity for BET family members BRD2, BRD3 and BRD4 among 7429 proteins detected. Degradation of BET bromodomains is associated with a more rapid and robust apoptotic response compared to bromodomain inhibition in primary human leukemic blasts, and dBET1 exhibits in vivo efficacy in a human leukemia xenograft. The reach of this approach is illustrated by a second *
![Research paper thumbnail of Faculty of 1000 evaluation for Discovery of a Plasmodium falciparum Glucose-6-phosphate Dehydrogenase 6-phosphogluconolactonase Inhibitor (R,Z)-N-((1-Ethylpyrrolidin-2-yl)methyl)-2-(2-fluorobenzylidene)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]thiazine-6-carboxamide (ML276) That Reduces Parasite Growth ...](https://attachments.academia-assets.com/118098919/thumbnails/1.jpg)
](F1000 - Post-publication peer review of the biomedical literature, 2012
Discovery of a Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase ... more Discovery of a Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase inhibitor (R,Z)-N-((1-ethylpyrrolidin-2-yl)methyl)-2-(2-fluorobenzylidene)-3-oxo-3,4dihydro-2H-benzo[b][1,4]thiazine-6-carboxamide (ML276) that reduces parasite growth in vitro
Cancer Genetics, 2016
Acquired aplastic anemia (aAA) results from the T cell-mediated autoimmune destruction of hematop... more Acquired aplastic anemia (aAA) results from the T cell-mediated autoimmune destruction of hematopoietic stem cells. Factors predicting response to immune suppression therapy (IST) or development of myelodysplastic syndrome (MDS) are beginning to be elucidated. Our recent data suggest most patients with aAA treated with IST develop clonal somatic genetic alterations in hematopoietic cells. One frequent acquired abnormality is copy-number neutral loss of heterozygosity on chromosome 6p (6p CN-LOH) involving the human leukocyte antigen (HLA) locus. We hypothesized that because 6p CN-LOH clones may arise from selective pressure to escape immune surveillance through deletion of HLA alleles, the development of 6p CN-LOH may affect response to IST. We used single nucleotide polymorphism array genotyping and targeted next-generation sequencing of HLA alleles to assess frequency of 6p CN-LOH, identity of HLA alleles lost through 6p CN-LOH, and impact of 6p CN-LOH on response to IST. 6p CN-LOH clones were present in 11.3% of patients, remained stable over time, and were not associated with development of MDS-defining cytogenetic abnormalities. Notably, no patient with 6p CN-LOH treated with IST achieved a complete response. In summary, clonal 6p CN-LOH in aAA defines a unique subgroup of patients that may provide insights into hematopoietic clonal evolution.
Cell stem cell, Jan 7, 2015
The transcription factor RUNX1 is frequently mutated in myelodysplastic syndrome and leukemia. RU... more The transcription factor RUNX1 is frequently mutated in myelodysplastic syndrome and leukemia. RUNX1 mutations can be early events, creating preleukemic stem cells that expand in the bone marrow. Here we show, counterintuitively, that Runx1-deficient hematopoietic stem and progenitor cells (HSPCs) have a slow growth, low biosynthetic, small cell phenotype and markedly reduced ribosome biogenesis (Ribi). The reduced Ribi involved decreased levels of rRNA and many mRNAs encoding ribosome proteins. Runx1 appears to directly regulate Ribi; Runx1 is enriched on the promoters of genes encoding ribosome proteins and binds the rDNA repeats. Runx1-deficient HSPCs have lower p53 levels, reduced apoptosis, an attenuated unfolded protein response, and accordingly are resistant to genotoxic and ER stress. The low biosynthetic activity and corresponding stress resistance provides a selective advantage to Runx1-deficient HSPCs, allowing them to expand in the bone marrow and outcompete normal HSPCs.
RNA, 2008
Production of ribosomes is a fundamental process that occurs in all dividing cells. It is a compl... more Production of ribosomes is a fundamental process that occurs in all dividing cells. It is a complex process consisting of the coordinated synthesis and assembly of four ribosomal RNAs (rRNA) with about 80 ribosomal proteins (r-proteins) involving more than 150 nonribosomal proteins and other factors. Diamond Blackfan anemia (DBA) is an inherited red cell aplasia caused by mutations in one of several r-proteins. How defects in r-proteins, essential for proliferation in all cells, lead to a human disease with a specific defect in red cell development is unknown. Here, we investigated the role of r-proteins in ribosome biogenesis in order to find out whether those mutated in DBA have any similarities. We depleted HeLa cells using siRNA for several individual r-proteins of the small (RPS6, RPS7, RPS15, RPS16, RPS17, RPS19, RPS24, RPS25, RPS28) or large subunit (RPL5, RPL7, RPL11, RPL14, RPL26, RPL35a) and studied the effect on rRNA processing and ribosome production. Depleting r-protein...
Proceedings of the National Academy of Sciences, 1993
Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal disorder arising in a multipotent hemopoiet... more Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal disorder arising in a multipotent hemopoietic stem cell. PNH manifests clinically with intravascular hemolysis resulting from an increased sensitivity of the red cells belonging to the PNH clone to complement-mediated lysis. Numerous studies have shown that surface proteins anchored to the membrane via a glycosylphosphatidylinositol (GPI) anchor (including proteins protecting the cell from complement) are deficient on the cells of the PNH clone, leading to the notion that GPI-anchor biosynthesis may be abnormal in these cells. To investigate the biochemical defect underlying PNH we have used lymphoblastoid cell lines (LCLs) with the PNH phenotype obtained by Epstein-Barr virus immortalization of lymphocytes from nine patients with PNH. By labeling cells with myo-[3H]inositol we have found that PNH LCLs produce phosphatidylinositol normally. By contrast, PNH LCLs fail to incorporate [3H]mannose into GPI anchor precursors. When cel...
Acta Crystallographica Section D Biological Crystallography, 1999
Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structur... more Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structure solved by molecular replacement. Crystals of the natural mutant R459L grow under similar conditions in space groups P212121 and C2221 with eight or four 515-residue molecules in the asymmetric unit, respectively. A non-crystallographic 222 tetramer was found in the C2221 crystal form using a 4 Å resolution data set and a dimer of the large β + α domains of the Leuconostoc mesenteroides enzyme as a search model. This tetramer was the only successful search model for the P212121 crystal form using data to 3 Å. Crystals of the deletion mutant ΔG6PD grow in space group F222 with a monomer in the asymmetric unit; 2.5 Å resolution data have been collected. Comparison of the packing of tetramers in the three space groups suggests that the N-terminal tail of the enzyme prevents crystallization with exact 222 molecular symmetry.
FEBS Letters, May 21, 2010
Dyskeratosis congenita (DC) was originally defined as a rare inherited bone marrow failure syndro... more Dyskeratosis congenita (DC) was originally defined as a rare inherited bone marrow failure syndrome associated with distinct mucocutaneous features. Today DC is defined by its pathogenetic mechanism and mutations in components of the telomere maintenance machinery resulting in excessively short telomeres in highly proliferating tissues. With this new definition the disease spectrum has broadened and ranges from intrauterine growth retardation, cerebellar hypoplasia, and death in early childhood to asymptomatic mutation carriers whose descendants are predisposed to malignancy, bone marrow failure, or pulmonary disease. The degree of telomere dysfunction is the major determinant of disease onset and manifestations.
F1000 - Post-publication peer review of the biomedical literature, 2014
Genome sequencing studies have shown that human malignancies often bear mutations in four or more... more Genome sequencing studies have shown that human malignancies often bear mutations in four or more driver genes 1 , but it is difficult to recapitulate this degree of genetic complexity in mouse models using conventional breeding. Here we use the CRISPR-Cas9 system of genome editing 2-4 to overcome this limitation. By delivering combinations of small guide RNAs (sgRNAs) and Cas9 with a lentiviral vector, we modified up to five genes in a single mouse hematopoietic stem cell (HSC), leading to clonal outgrowth and myeloid malignancy. We thereby generated models of acute myeloid leukemia (AML) with cooperating mutations in genes encoding epigenetic modifiers, transcription factors, and mediators of cytokine signaling, recapitulating the combinations of mutations observed in the human disease. Our results suggest that lentivirusdelivered sgRNA:Cas9 genome editing should be useful to engineer a broad array of in vivo cancer models that better reflect the complexity of human disease. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
F1000Research, 2014
We describe a case of paroxysmal nocturnal hemoglobinuria (PNH) in a woman who is heterozygous fo... more We describe a case of paroxysmal nocturnal hemoglobinuria (PNH) in a woman who is heterozygous for the glucose-6-phosphate dehydrogenase A- (G6PDA-) allele. PNH is associated with one or more clones of cells that lack complement inhibition due to loss of function somatic mutations in the PIGA gene. PIGA encodes the enzyme phosphatidylinositol glycan anchor biosynthesis, class A, which catalyses the first step of glycosylphosphatidylinisotol (GPI) anchor synthesis. Two GPI anchored red cell surface antigens regulate complement lysis. G6PD catalyses the first step of the pentose phosphate pathway and enzyme variants, frequent in some populations have been because they confer resistance to malaria, are associated with hemolysis in the presence of oxidizing agents including several drugs. The patient had suffered a hemolytic attack after taking Bactrim, a drug that precipitates hemolysis in G6PD deficient individuals. Since both G6PD and PIGA are X-linked we hypothesized that the PI...
Proceedings of the National Academy of Sciences, 1991
The human X chromosome-linked gene encoding glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49)... more The human X chromosome-linked gene encoding glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49) is known to be highly polymorphic from the biochemical characterization of enzyme variants. The variant A (with enzyme activity in the normal range) and the variant A- (associated with enzyme deficiency) each have a frequency of about 0.2 in several African populations. Two restriction fragment length polymorphisms have also been found in people of African descent, but not in other populations, whereas a silent mutation has been shown to be polymorphic in Mediterranean, Middle Eastern, African, and Indian populations. We report now on two additional polymorphisms that we have detected by sequence analysis, one in intron 7 and one in intron 8. The analysis of 54 African male subjects for the seven polymorphic sites, clustered within 3 kilobases of the G6PD gene, has revealed only 7 of the 128 possible haplotypes, indicating marked linkage disequilibrium. These data have enabled us to sug...
Molecular Microbiology, 1997
Journal of Medical Genetics, 1998
Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the early onset of reti... more Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the early onset of reticulate skin pigmentation, nail dystrophy, and mucosal leucoplakia. In over 80% of cases bone marrow failure develops and this is the main cause of early mortality. The DCI gene responsible for the X linked form (MIM 305000) of dyskeratosis congenita has been mapped to Xq28. In order to narrow the candidate gene region, genetic linkage analysis was performed in eight X linked pedigrees using a set of markers spanning Xq28. A maximum lod score of 5.31 with no recombinations was achieved with marker DXS1073. Two recombination events were identified; one ofthese uses X chromosome inactivation pattern analysis to determine carrier status and haplotype analysis to fine map the recombination breakpoint. The fine mapping of these recombination events has enabled the candidate gene region for X linked dyskeratosis congenita to be defined as the 1.4 Mb interval between Xq3274 and DXS1 108. (7Med Genet 1998;35:993-996
Journal of Clinical Investigation, 1992
To characterize the autoantigen of Goodpasture's (anti-glomerular basement membrane) disease, a m... more To characterize the autoantigen of Goodpasture's (anti-glomerular basement membrane) disease, a molecule of 26-kD reactive with autoantibodies from patients' sera was purified from collagenase digests of sheep glomerular basement membrane. Short internal amino acid sequences were obtained after tryptic or cyanogen bromide cleavage, and used to deduce redundant oligonucleotides for use in the polymerase chain reaction on cDNA derived from sheep renal cortex. Molecules of 175 bp were amplified and found to come from two cDNA sequences. One was identical to that of a type IV collagen chain (a5) cloned from human placenta and shown to be expressed in human kidney. The other was from a type IV collagen chain with close similarities to al and a5 chains, and was used to obtain human cDNA sequences by cDNA library screening and by further polymerase chain reaction amplifications. The correspondence of the derived amino acid sequence of the new chain with published protein and cDNA sequences shows it to be the a3 chain oftype IV collagen. Its gene, COL4A3, maps to 2q36-2q37. The primary sequence and other characteristics of this chain confirm that it carries the Goodpasture antigen. (J.
Best Practice & Research Clinical Haematology, 2000
Glucose-6-phosphate dehydrogenase (G6PD) is expressed in all tissues, where it catalyses the firs... more Glucose-6-phosphate dehydrogenase (G6PD) is expressed in all tissues, where it catalyses the first step in the pentose phosphate pathway. G6PD deficiency is prevalent throughout tropical and subtropical regions of the world because of the protection it affords during malaria infection. Although most affected individuals are asymptomatic, there is a risk of neonatal jaundice and acute haemolytic anaemia, triggered by infection
Annals of Medicine, Jun 3, 2014
The inherited bone marrow failure syndromes are a diverse group of genetic diseases associated wi... more The inherited bone marrow failure syndromes are a diverse group of genetic diseases associated with inadequate production of one or more blood cell lineages. Examples include Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan anemia, thrombocytopenia absent radii syndrome, severe congenital neutropenia, and Shwachman-Diamond syndrome. The management of these disorders was once the exclusive domain of pediatric subspecialists, but increasingly physicians who care for adults are being called upon to diagnose or treat these conditions. Through a series of patient vignettes, we highlight the clinical manifestations of inherited bone marrow failure syndromes in adolescents and young adults. The diagnostic and therapeutic challenges posed by these diseases are discussed.
Acta Crystallographica Section D-biological Crystallography, Apr 1, 1999
Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structur... more Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structure solved by molecular replacement. Crystals of the natural mutant R459L grow under similar conditions in space groups P2 1 2 1 2 1 and C222 1 with eight or four 515-residue molecules in the asymmetric unit, respectively. A non-crystallographic 222 tetramer was found in the C222 1 crystal form using a 4 A Ê resolution data set and a dimer of the large + domains of the Leuconostoc mesenteroides enzyme as a search model. This tetramer was the only successful search model for the P2 1 2 1 2 1 crystal form using data to 3 A Ê. Crystals of the deletion mutant ÁG6PD grow in space group F222 with a monomer in the asymmetric unit; 2.5 A Ê resolution data have been collected. Comparison of the packing of tetramers in the three space groups suggests that the N-terminal tail of the enzyme prevents crystallization with exact 222 molecular symmetry.
F1000 - Post-publication peer review of the biomedical literature, 2016
Small-molecule antagonists disable discrete biochemical properties of protein targets. For multid... more Small-molecule antagonists disable discrete biochemical properties of protein targets. For multidomain protein targets, the pharmacologic consequence of drug action is limited by selective disruption of one domain-specific activity. More broadly, target inhibition is kinetically limited by the durability and degree of target engagement. These features of traditional drug molecules are challenging to the development of inhibitors targeting transcription factors and chromatinassociated epigenetic proteins, which function as multi-domain biomolecular scaffolds and generally feature rapid association and dissociation kinetics. We therefore devised a chemical strategy to prompt ligand-dependent target protein degradation, via chemical conjugation with derivatized phthalimides that hijack the function of the Cereblon E3 ubiquitin ligase complex. Using this approach, we converted an acetyl-lysine competitive antagonist that displaces BET bromodomains from chromatin (JQ1) to a phthalimide-conjugated ligand that prompts immediate Cereblon-dependent BET protein degradation (dBET1). Expression proteomics confirms high specificity for BET family members BRD2, BRD3 and BRD4 among 7429 proteins detected. Degradation of BET bromodomains is associated with a more rapid and robust apoptotic response compared to bromodomain inhibition in primary human leukemic blasts, and dBET1 exhibits in vivo efficacy in a human leukemia xenograft. The reach of this approach is illustrated by a second *
F1000 - Post-publication peer review of the biomedical literature, 2012
Discovery of a Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase ... more Discovery of a Plasmodium falciparum glucose-6-phosphate dehydrogenase 6-phosphogluconolactonase inhibitor (R,Z)-N-((1-ethylpyrrolidin-2-yl)methyl)-2-(2-fluorobenzylidene)-3-oxo-3,4dihydro-2H-benzo[b][1,4]thiazine-6-carboxamide (ML276) that reduces parasite growth in vitro
Cancer Genetics, 2016
Acquired aplastic anemia (aAA) results from the T cell-mediated autoimmune destruction of hematop... more Acquired aplastic anemia (aAA) results from the T cell-mediated autoimmune destruction of hematopoietic stem cells. Factors predicting response to immune suppression therapy (IST) or development of myelodysplastic syndrome (MDS) are beginning to be elucidated. Our recent data suggest most patients with aAA treated with IST develop clonal somatic genetic alterations in hematopoietic cells. One frequent acquired abnormality is copy-number neutral loss of heterozygosity on chromosome 6p (6p CN-LOH) involving the human leukocyte antigen (HLA) locus. We hypothesized that because 6p CN-LOH clones may arise from selective pressure to escape immune surveillance through deletion of HLA alleles, the development of 6p CN-LOH may affect response to IST. We used single nucleotide polymorphism array genotyping and targeted next-generation sequencing of HLA alleles to assess frequency of 6p CN-LOH, identity of HLA alleles lost through 6p CN-LOH, and impact of 6p CN-LOH on response to IST. 6p CN-LOH clones were present in 11.3% of patients, remained stable over time, and were not associated with development of MDS-defining cytogenetic abnormalities. Notably, no patient with 6p CN-LOH treated with IST achieved a complete response. In summary, clonal 6p CN-LOH in aAA defines a unique subgroup of patients that may provide insights into hematopoietic clonal evolution.
Cell stem cell, Jan 7, 2015
The transcription factor RUNX1 is frequently mutated in myelodysplastic syndrome and leukemia. RU... more The transcription factor RUNX1 is frequently mutated in myelodysplastic syndrome and leukemia. RUNX1 mutations can be early events, creating preleukemic stem cells that expand in the bone marrow. Here we show, counterintuitively, that Runx1-deficient hematopoietic stem and progenitor cells (HSPCs) have a slow growth, low biosynthetic, small cell phenotype and markedly reduced ribosome biogenesis (Ribi). The reduced Ribi involved decreased levels of rRNA and many mRNAs encoding ribosome proteins. Runx1 appears to directly regulate Ribi; Runx1 is enriched on the promoters of genes encoding ribosome proteins and binds the rDNA repeats. Runx1-deficient HSPCs have lower p53 levels, reduced apoptosis, an attenuated unfolded protein response, and accordingly are resistant to genotoxic and ER stress. The low biosynthetic activity and corresponding stress resistance provides a selective advantage to Runx1-deficient HSPCs, allowing them to expand in the bone marrow and outcompete normal HSPCs.
RNA, 2008
Production of ribosomes is a fundamental process that occurs in all dividing cells. It is a compl... more Production of ribosomes is a fundamental process that occurs in all dividing cells. It is a complex process consisting of the coordinated synthesis and assembly of four ribosomal RNAs (rRNA) with about 80 ribosomal proteins (r-proteins) involving more than 150 nonribosomal proteins and other factors. Diamond Blackfan anemia (DBA) is an inherited red cell aplasia caused by mutations in one of several r-proteins. How defects in r-proteins, essential for proliferation in all cells, lead to a human disease with a specific defect in red cell development is unknown. Here, we investigated the role of r-proteins in ribosome biogenesis in order to find out whether those mutated in DBA have any similarities. We depleted HeLa cells using siRNA for several individual r-proteins of the small (RPS6, RPS7, RPS15, RPS16, RPS17, RPS19, RPS24, RPS25, RPS28) or large subunit (RPL5, RPL7, RPL11, RPL14, RPL26, RPL35a) and studied the effect on rRNA processing and ribosome production. Depleting r-protein...
Proceedings of the National Academy of Sciences, 1993
Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal disorder arising in a multipotent hemopoiet... more Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal disorder arising in a multipotent hemopoietic stem cell. PNH manifests clinically with intravascular hemolysis resulting from an increased sensitivity of the red cells belonging to the PNH clone to complement-mediated lysis. Numerous studies have shown that surface proteins anchored to the membrane via a glycosylphosphatidylinositol (GPI) anchor (including proteins protecting the cell from complement) are deficient on the cells of the PNH clone, leading to the notion that GPI-anchor biosynthesis may be abnormal in these cells. To investigate the biochemical defect underlying PNH we have used lymphoblastoid cell lines (LCLs) with the PNH phenotype obtained by Epstein-Barr virus immortalization of lymphocytes from nine patients with PNH. By labeling cells with myo-[3H]inositol we have found that PNH LCLs produce phosphatidylinositol normally. By contrast, PNH LCLs fail to incorporate [3H]mannose into GPI anchor precursors. When cel...
Acta Crystallographica Section D Biological Crystallography, 1999
Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structur... more Recombinant human glucose 6-phosphate dehydrogenase (G6PD) has been crystallized and its structure solved by molecular replacement. Crystals of the natural mutant R459L grow under similar conditions in space groups P212121 and C2221 with eight or four 515-residue molecules in the asymmetric unit, respectively. A non-crystallographic 222 tetramer was found in the C2221 crystal form using a 4 Å resolution data set and a dimer of the large β + α domains of the Leuconostoc mesenteroides enzyme as a search model. This tetramer was the only successful search model for the P212121 crystal form using data to 3 Å. Crystals of the deletion mutant ΔG6PD grow in space group F222 with a monomer in the asymmetric unit; 2.5 Å resolution data have been collected. Comparison of the packing of tetramers in the three space groups suggests that the N-terminal tail of the enzyme prevents crystallization with exact 222 molecular symmetry.
FEBS Letters, May 21, 2010
Dyskeratosis congenita (DC) was originally defined as a rare inherited bone marrow failure syndro... more Dyskeratosis congenita (DC) was originally defined as a rare inherited bone marrow failure syndrome associated with distinct mucocutaneous features. Today DC is defined by its pathogenetic mechanism and mutations in components of the telomere maintenance machinery resulting in excessively short telomeres in highly proliferating tissues. With this new definition the disease spectrum has broadened and ranges from intrauterine growth retardation, cerebellar hypoplasia, and death in early childhood to asymptomatic mutation carriers whose descendants are predisposed to malignancy, bone marrow failure, or pulmonary disease. The degree of telomere dysfunction is the major determinant of disease onset and manifestations.
F1000 - Post-publication peer review of the biomedical literature, 2014
Genome sequencing studies have shown that human malignancies often bear mutations in four or more... more Genome sequencing studies have shown that human malignancies often bear mutations in four or more driver genes 1 , but it is difficult to recapitulate this degree of genetic complexity in mouse models using conventional breeding. Here we use the CRISPR-Cas9 system of genome editing 2-4 to overcome this limitation. By delivering combinations of small guide RNAs (sgRNAs) and Cas9 with a lentiviral vector, we modified up to five genes in a single mouse hematopoietic stem cell (HSC), leading to clonal outgrowth and myeloid malignancy. We thereby generated models of acute myeloid leukemia (AML) with cooperating mutations in genes encoding epigenetic modifiers, transcription factors, and mediators of cytokine signaling, recapitulating the combinations of mutations observed in the human disease. Our results suggest that lentivirusdelivered sgRNA:Cas9 genome editing should be useful to engineer a broad array of in vivo cancer models that better reflect the complexity of human disease. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
F1000Research, 2014
We describe a case of paroxysmal nocturnal hemoglobinuria (PNH) in a woman who is heterozygous fo... more We describe a case of paroxysmal nocturnal hemoglobinuria (PNH) in a woman who is heterozygous for the glucose-6-phosphate dehydrogenase A- (G6PDA-) allele. PNH is associated with one or more clones of cells that lack complement inhibition due to loss of function somatic mutations in the PIGA gene. PIGA encodes the enzyme phosphatidylinositol glycan anchor biosynthesis, class A, which catalyses the first step of glycosylphosphatidylinisotol (GPI) anchor synthesis. Two GPI anchored red cell surface antigens regulate complement lysis. G6PD catalyses the first step of the pentose phosphate pathway and enzyme variants, frequent in some populations have been because they confer resistance to malaria, are associated with hemolysis in the presence of oxidizing agents including several drugs. The patient had suffered a hemolytic attack after taking Bactrim, a drug that precipitates hemolysis in G6PD deficient individuals. Since both G6PD and PIGA are X-linked we hypothesized that the PI...
Proceedings of the National Academy of Sciences, 1991
The human X chromosome-linked gene encoding glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49)... more The human X chromosome-linked gene encoding glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49) is known to be highly polymorphic from the biochemical characterization of enzyme variants. The variant A (with enzyme activity in the normal range) and the variant A- (associated with enzyme deficiency) each have a frequency of about 0.2 in several African populations. Two restriction fragment length polymorphisms have also been found in people of African descent, but not in other populations, whereas a silent mutation has been shown to be polymorphic in Mediterranean, Middle Eastern, African, and Indian populations. We report now on two additional polymorphisms that we have detected by sequence analysis, one in intron 7 and one in intron 8. The analysis of 54 African male subjects for the seven polymorphic sites, clustered within 3 kilobases of the G6PD gene, has revealed only 7 of the 128 possible haplotypes, indicating marked linkage disequilibrium. These data have enabled us to sug...
Molecular Microbiology, 1997
Journal of Medical Genetics, 1998
Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the early onset of reti... more Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the early onset of reticulate skin pigmentation, nail dystrophy, and mucosal leucoplakia. In over 80% of cases bone marrow failure develops and this is the main cause of early mortality. The DCI gene responsible for the X linked form (MIM 305000) of dyskeratosis congenita has been mapped to Xq28. In order to narrow the candidate gene region, genetic linkage analysis was performed in eight X linked pedigrees using a set of markers spanning Xq28. A maximum lod score of 5.31 with no recombinations was achieved with marker DXS1073. Two recombination events were identified; one ofthese uses X chromosome inactivation pattern analysis to determine carrier status and haplotype analysis to fine map the recombination breakpoint. The fine mapping of these recombination events has enabled the candidate gene region for X linked dyskeratosis congenita to be defined as the 1.4 Mb interval between Xq3274 and DXS1 108. (7Med Genet 1998;35:993-996
Journal of Clinical Investigation, 1992
To characterize the autoantigen of Goodpasture's (anti-glomerular basement membrane) disease, a m... more To characterize the autoantigen of Goodpasture's (anti-glomerular basement membrane) disease, a molecule of 26-kD reactive with autoantibodies from patients' sera was purified from collagenase digests of sheep glomerular basement membrane. Short internal amino acid sequences were obtained after tryptic or cyanogen bromide cleavage, and used to deduce redundant oligonucleotides for use in the polymerase chain reaction on cDNA derived from sheep renal cortex. Molecules of 175 bp were amplified and found to come from two cDNA sequences. One was identical to that of a type IV collagen chain (a5) cloned from human placenta and shown to be expressed in human kidney. The other was from a type IV collagen chain with close similarities to al and a5 chains, and was used to obtain human cDNA sequences by cDNA library screening and by further polymerase chain reaction amplifications. The correspondence of the derived amino acid sequence of the new chain with published protein and cDNA sequences shows it to be the a3 chain oftype IV collagen. Its gene, COL4A3, maps to 2q36-2q37. The primary sequence and other characteristics of this chain confirm that it carries the Goodpasture antigen. (J.
Best Practice & Research Clinical Haematology, 2000
Glucose-6-phosphate dehydrogenase (G6PD) is expressed in all tissues, where it catalyses the firs... more Glucose-6-phosphate dehydrogenase (G6PD) is expressed in all tissues, where it catalyses the first step in the pentose phosphate pathway. G6PD deficiency is prevalent throughout tropical and subtropical regions of the world because of the protection it affords during malaria infection. Although most affected individuals are asymptomatic, there is a risk of neonatal jaundice and acute haemolytic anaemia, triggered by infection