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Rodriguez-Sevilla JJ, Calvo X, Arenillas L. Causes and Pathophysiology of Acquired Sideroblastic Anemia. Genes (Basel) 2022; 13:genes13091562. [PMID: 36140729 PMCID: PMC9498732 DOI: 10.3390/genes13091562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/22/2022] [Accepted: 08/26/2022] [Indexed: 01/19/2023] Open
Abstract
The sideroblastic anemias are a heterogeneous group of inherited and acquired disorders characterized by anemia and the presence of ring sideroblasts in the bone marrow. Ring sideroblasts are abnormal erythroblasts with iron-loaded mitochondria that are visualized by Prussian blue staining as a perinuclear ring of green-blue granules. The mechanisms that lead to the ring sideroblast formation are heterogeneous, but in all of them, there is an abnormal deposition of iron in the mitochondria of erythroblasts. Congenital sideroblastic anemias include nonsyndromic and syndromic disorders. Acquired sideroblastic anemias include conditions that range from clonal disorders (myeloid neoplasms as myelodysplastic syndromes and myelodysplastic/myeloproliferative neoplasms with ring sideroblasts) to toxic or metabolic reversible sideroblastic anemia. In the last 30 years, due to the advances in genomic techniques, a deep knowledge of the pathophysiological mechanisms has been accomplished and the bases for possible targeted treatments have been established. The distinction between the different forms of sideroblastic anemia is based on the study of the characteristics of the anemia, age of diagnosis, clinical manifestations, and the performance of laboratory analysis involving genetic testing in many cases. This review focuses on the differential diagnosis of acquired disorders associated with ring sideroblasts.
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Affiliation(s)
| | - Xavier Calvo
- Laboratori de Citologia Hematològica, Department of Pathology, Hospital del Mar, 08003 Barcelona, Spain
- Group of Translational Research on Hematological Neoplasms (GRETNHE), IMIM-Hospital del Mar, 08003 Barcelona, Spain
| | - Leonor Arenillas
- Laboratori de Citologia Hematològica, Department of Pathology, Hospital del Mar, 08003 Barcelona, Spain
- Group of Translational Research on Hematological Neoplasms (GRETNHE), IMIM-Hospital del Mar, 08003 Barcelona, Spain
- Correspondence: ; Tel.: +349-3248-3036; Fax: +349-3248-3131
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Nomura K, Kitagawa Y, Aihara M, Ohki Y, Furuyama K, Hirokawa T. Heme-dependent recognition of 5-aminolevulinate synthase by the human mitochondrial molecular chaperone ClpX. FEBS Lett 2021; 595:3019-3029. [PMID: 34704252 DOI: 10.1002/1873-3468.14214] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 09/21/2021] [Accepted: 10/15/2021] [Indexed: 11/08/2022]
Abstract
The caseinolytic mitochondrial matrix peptidase chaperone subunit (ClpX) plays an important role in the heme-dependent regulation of 5-aminolevulinate synthase (ALAS1), a key enzyme in heme biosynthesis. However, the mechanisms underlying the role of ClpX in this process remain unclear. In this in vitro study, we confirmed the direct binding between ALAS1 and ClpX in a heme-dependent manner. The substitution of C108 P109 [CP motif 3 (CP3)] with A108 A109 in ALAS1 resulted in a loss of ability to bind ClpX. Computational disorder analyses revealed that CP3 was located in a potential intrinsically disordered protein region (IDPR). Thus, we propose that conditional disorder-to-order transitions in the IDPRs of ALAS1 may represent key mechanisms underlying the heme-dependent recognition of ALAS1 by ClpX.
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Affiliation(s)
- Kazumi Nomura
- Department of Molecular Biochemistry, Iwate Medical University, Japan
| | - Yu Kitagawa
- Department of Molecular Biochemistry, Iwate Medical University, Japan
| | - Marina Aihara
- Department of Molecular Biochemistry, Iwate Medical University, Japan
| | - Yusuke Ohki
- Department of Molecular Biochemistry, Iwate Medical University, Japan
| | | | - Takatsugu Hirokawa
- Division of Biomedical Science, Faculty of Medicine, University of Tsukuba, Japan.,Transborder Medical Research Center, Faculty of Medicine, University of Tsukuba, Japan.,Cellular and Molecular Biotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan
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Huang J, Ge M, Shao Y, Wang M, Jin P, Huo J, Li X, Zhang J, Nie N, Zheng Y. A hemizygous p.R204Q mutation in the ALAS2 gene underlies X-linked sideroblastic anemia in an adult Chinese Han man. BMC Med Genomics 2021; 14:107. [PMID: 33858445 PMCID: PMC8048311 DOI: 10.1186/s12920-021-00950-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 03/23/2021] [Indexed: 12/04/2022] Open
Abstract
Background X-linked sideroblastic anemia (XLSA) is the most common form of congenital sideroblastic anemia (CSA), and is associated with the mutations in the 5-aminolevulinate synthase 2 (ALAS2). The genetic basis of more than 40% of CSA cases remains unknown. Methods A two-generation Chinese family with XLSA was studied by next-generation sequencing to identify the underlying CSA-related mutations. Results In the study, we identified a missense ALAS2 R204Q mutation in a hemizygous Chinese Han man and in his heterozygous daughter. The male proband presented clinical manifestations at 38 years old and had a good response to pyridoxine. Conclusions XLSA, as a hereditary disease, can present clinical manifestations later in lives, for adult male patients with ringed sideroblasts and hypochromic anemia, it should be evaluated with gene analyses to exclude CSA. Supplementary Information The online version contains supplementary material available at 10.1186/s12920-021-00950-x.
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Affiliation(s)
- Jinbo Huang
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Meili Ge
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China.
| | - Yingqi Shao
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Min Wang
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Peng Jin
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Jiali Huo
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Xingxin Li
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Jing Zhang
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Neng Nie
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
| | - Yizhou Zheng
- State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Science and Peking Union Medical College, 288 Nanjing Road, Tianjin, 300020, People's Republic of China
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Genome-wide microhomologies enable precise template-free editing of biologically relevant deletion mutations. Nat Commun 2019; 10:4856. [PMID: 31649251 PMCID: PMC6813315 DOI: 10.1038/s41467-019-12829-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 09/30/2019] [Indexed: 02/06/2023] Open
Abstract
The functional effect of a gene edit by designer nucleases depends on the DNA repair outcome at the targeted locus. While non-homologous end joining (NHEJ) repair results in various mutations, microhomology-mediated end joining (MMEJ) creates precise deletions based on the alignment of flanking microhomologies (µHs). Recently, the sequence context surrounding nuclease-induced double strand breaks (DSBs) has been shown to predict repair outcomes, for which µH plays an important role. Here, we survey naturally occurring human deletion variants and identify that 11 million or 57% are flanked by µHs, covering 88% of protein-coding genes. These biologically relevant mutations are candidates for precise creation in a template-free manner by MMEJ repair. Using CRISPR-Cas9 in human induced pluripotent stem cells (hiPSCs), we efficiently create pathogenic deletion mutations for demonstrable disease models with both gain- and loss-of-function phenotypes. We anticipate this dataset and gene editing strategy to enable functional genetic studies and drug screening.
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Sachar M, Anderson KE, Ma X. Protoporphyrin IX: the Good, the Bad, and the Ugly. J Pharmacol Exp Ther 2015; 356:267-75. [PMID: 26588930 DOI: 10.1124/jpet.115.228130] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 11/20/2015] [Indexed: 01/10/2023] Open
Abstract
Protoporphyrin IX (PPIX) is ubiquitously present in all living cells in small amounts as a precursor of heme. PPIX has some biologic functions of its own, and PPIX-based strategies have been used for cancer diagnosis and treatment (the good). PPIX serves as the substrate for ferrochelatase, the final enzyme in heme biosynthesis, and its homeostasis is tightly regulated during heme synthesis. Accumulation of PPIX in human porphyrias can cause skin photosensitivity, biliary stones, hepatobiliary damage, and even liver failure (the bad and the ugly). In this work, we review the mechanisms that are associated with the broad aspects of PPIX. Because PPIX is a hydrophobic molecule, its disposition is by hepatic rather than renal excretion. Large amounts of PPIX are toxic to the liver and can cause cholestatic liver injury. Application of PPIX in cancer diagnosis and treatment is based on its photodynamic effects.
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Affiliation(s)
- Madhav Sachar
- Department of Pharmaceutical Sciences, Center for Pharmacogenetics, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania (M.S., X.M.); and Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, Texas (K.E.A.)
| | - Karl E Anderson
- Department of Pharmaceutical Sciences, Center for Pharmacogenetics, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania (M.S., X.M.); and Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, Texas (K.E.A.)
| | - Xiaochao Ma
- Department of Pharmaceutical Sciences, Center for Pharmacogenetics, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania (M.S., X.M.); and Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, Texas (K.E.A.)
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Biology of Heme in Mammalian Erythroid Cells and Related Disorders. BIOMED RESEARCH INTERNATIONAL 2015; 2015:278536. [PMID: 26557657 PMCID: PMC4628764 DOI: 10.1155/2015/278536] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 06/14/2015] [Indexed: 01/19/2023]
Abstract
Heme is a prosthetic group comprising ferrous iron (Fe(2+)) and protoporphyrin IX and is an essential cofactor in various biological processes such as oxygen transport (hemoglobin) and storage (myoglobin) and electron transfer (respiratory cytochromes) in addition to its role as a structural component of hemoproteins. Heme biosynthesis is induced during erythroid differentiation and is coordinated with the expression of genes involved in globin formation and iron acquisition/transport. However, erythroid and nonerythroid cells exhibit distinct differences in the heme biosynthetic pathway regulation. Defects of heme biosynthesis in developing erythroblasts can have profound medical implications, as represented by sideroblastic anemia. This review will focus on the biology of heme in mammalian erythroid cells, including the heme biosynthetic pathway as well as the regulatory role of heme and human disorders that arise from defective heme synthesis.
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Stehling O, Wilbrecht C, Lill R. Mitochondrial iron-sulfur protein biogenesis and human disease. Biochimie 2014; 100:61-77. [PMID: 24462711 DOI: 10.1016/j.biochi.2014.01.010] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 01/13/2014] [Indexed: 12/29/2022]
Abstract
Work during the past 14 years has shown that mitochondria are the primary site for the biosynthesis of iron-sulfur (Fe/S) clusters. In fact, it is this process that renders mitochondria essential for viability of virtually all eukaryotes, because they participate in the synthesis of the Fe/S clusters of key nuclear and cytosolic proteins such as DNA polymerases, DNA helicases, and ABCE1 (Rli1), an ATPase involved in protein synthesis. As a consequence, mitochondrial function is crucial for nuclear DNA synthesis and repair, ribosomal protein synthesis, and numerous other extra-mitochondrial pathways including nucleotide metabolism and cellular iron regulation. Within mitochondria, the synthesis of Fe/S clusters and their insertion into apoproteins is assisted by 17 proteins forming the ISC (iron-sulfur cluster) assembly machinery. Biogenesis of mitochondrial Fe/S proteins can be dissected into three main steps: First, a Fe/S cluster is generated de novo on a scaffold protein. Second, the Fe/S cluster is dislocated from the scaffold and transiently bound to transfer proteins. Third, the latter components, together with specific ISC targeting factors insert the Fe/S cluster into client apoproteins. Disturbances of the first two steps impair the maturation of extra-mitochondrial Fe/S proteins and affect cellular and systemic iron homeostasis. In line with the essential function of mitochondria, genetic mutations in a number of ISC genes lead to severe neurological, hematological and metabolic diseases, often with a fatal outcome in early childhood. In this review we briefly summarize our current functional knowledge on the ISC assembly machinery, and we present a comprehensive overview of the various Fe/S protein assembly diseases.
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Affiliation(s)
- Oliver Stehling
- Institut für Zytobiologie, Philipps-Universität Marburg, Robert-Koch-Str. 6, 35032 Marburg, Germany
| | - Claudia Wilbrecht
- Institut für Zytobiologie, Philipps-Universität Marburg, Robert-Koch-Str. 6, 35032 Marburg, Germany
| | - Roland Lill
- Institut für Zytobiologie, Philipps-Universität Marburg, Robert-Koch-Str. 6, 35032 Marburg, Germany; Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Str. 10, 35043 Marburg, Germany; LOEWE Zentrum für Synthetische Mikrobiologie SynMikro, Hans-Meerwein-Str., 35043 Marburg, Germany.
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Kaneko K, Furuyama K, Fujiwara T, Kobayashi R, Ishida H, Harigae H, Shibahara S. Identification of a novel erythroid-specific enhancer for the ALAS2 gene and its loss-of-function mutation which is associated with congenital sideroblastic anemia. Haematologica 2013; 99:252-61. [PMID: 23935018 DOI: 10.3324/haematol.2013.085449] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Erythroid-specific 5-aminolevulinate synthase (ALAS2) is the rate-limiting enzyme for heme biosynthesis in erythroid cells, and a missense mutation of the ALAS2 gene is associated with congenital sideroblastic anemia. However, the gene responsible for this form of anemia remains unclear in about 40% of patients. Here, we identify a novel erythroid-specific enhancer of 130 base pairs in the first intron of the ALAS2 gene. The newly identified enhancer contains a cis-acting element that is bound by the erythroid-specific transcription factor GATA1, as confirmed by chromatin immunoprecipitation analysis in vivo and by electrophoretic mobility shift assay in vitro. A promoter activity assay in K562 human erythroleukemia cells revealed that the presence of this 130-base pair region increased the promoter activity of the ALAS2 gene by 10-15-fold. Importantly, two mutations, each of which disrupts the GATA-binding site in the enhancer, were identified in unrelated male patients with congenital sideroblastic anemia, and the lower expression level of ALAS2 mRNA in bone marrow erythroblasts was confirmed in one of these patients. Moreover, GATA1 failed to bind to each mutant sequence at the GATA-binding site, and each mutation abolished the enhancer function on ALAS2 promoter activity in K562 cells. Thus, a mutation at the GATA-binding site in this enhancer may cause congenital sideroblastic anemia. These results suggest that the newly identified intronic enhancer is essential for the expression of the ALAS2 gene in erythroid cells. We propose that the 130-base pair enhancer region located in the first intron of the ALAS2 gene should be examined in patients with congenital sideroblastic anemia in whom the gene responsible is unknown.
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A systematic comparison and evaluation of high density exon arrays and RNA-seq technology used to unravel the peripheral blood transcriptome of sickle cell disease. BMC Med Genomics 2012; 5:28. [PMID: 22747986 PMCID: PMC3428653 DOI: 10.1186/1755-8794-5-28] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 06/29/2012] [Indexed: 01/02/2023] Open
Abstract
Background Transcriptomic studies in clinical research are essential tools for deciphering the functional elements of the genome and unraveling underlying disease mechanisms. Various technologies have been developed to deduce and quantify the transcriptome including hybridization and sequencing-based approaches. Recently, high density exon microarrays have been successfully employed for detecting differentially expressed genes and alternative splicing events for biomarker discovery and disease diagnostics. The field of transcriptomics is currently being revolutionized by high throughput DNA sequencing methodologies to map, characterize, and quantify the transcriptome. Methods In an effort to understand the merits and limitations of each of these tools, we undertook a study of the transcriptome in sickle cell disease, a monogenic disease comparing the Affymetrix Human Exon 1.0 ST microarray (Exon array) and Illumina’s deep sequencing technology (RNA-seq) on whole blood clinical specimens. Results Analysis indicated a strong concordance (R = 0.64) between Exon array and RNA-seq data at both gene level and exon level transcript expression. The magnitude of differential expression was found to be generally higher in RNA-seq than in the Exon microarrays. We also demonstrate for the first time the ability of RNA-seq technology to discover novel transcript variants and differential expression in previously unannotated genomic regions in sickle cell disease. In addition to detecting expression level changes, RNA-seq technology was also able to identify sequence variation in the expressed transcripts. Conclusions Our findings suggest that microarrays remain useful and accurate for transcriptomic analysis of clinical samples with low input requirements, while RNA-seq technology complements and extends microarray measurements for novel discoveries.
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Sheftel AD, Mason AB, Ponka P. The long history of iron in the Universe and in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1820:161-87. [PMID: 21856378 PMCID: PMC3258305 DOI: 10.1016/j.bbagen.2011.08.002] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/19/2011] [Accepted: 08/01/2011] [Indexed: 12/21/2022]
Abstract
BACKGROUND Not long after the Big Bang, iron began to play a central role in the Universe and soon became mired in the tangle of biochemistry that is the prima essentia of life. Since life's addiction to iron transcends the oxygenation of the Earth's atmosphere, living things must be protected from the potentially dangerous mix of iron and oxygen. The human being possesses grams of this potentially toxic transition metal, which is shuttling through his oxygen-rich humor. Since long before the birth of modern medicine, the blood-vibrant red from a massive abundance of hemoglobin iron-has been a focus for health experts. SCOPE OF REVIEW We describe the current understanding of iron metabolism, highlight the many important discoveries that accreted this knowledge, and describe the perils of dysfunctional iron handling. GENERAL SIGNIFICANCE Isaac Newton famously penned, "If I have seen further than others, it is by standing upon the shoulders of giants". We hope that this review will inspire future scientists to develop intellectual pursuits by understanding the research and ideas from many remarkable thinkers of the past. MAJOR CONCLUSIONS The history of iron research is a long, rich story with early beginnings, and is far from being finished. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Alex D. Sheftel
- University of Ottawa Heart Institute, 40 Ruskin St., Ottawa, ON K1Y 4W7, Canada
| | - Anne B. Mason
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
| | - Prem Ponka
- Lady Davis Institute for Medical Research, Jewish General Hospital, 3755 Côte-Ste.-Catherine Rd., Montréal, QC H3T 1E2, and Departments of Physiology and Medicine, McGill University, Montréal, QC, Canada
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Furuyama K, Kaneko K, Vargas PD. Heme as a magnificent molecule with multiple missions: heme determines its own fate and governs cellular homeostasis. TOHOKU J EXP MED 2007; 213:1-16. [PMID: 17785948 DOI: 10.1620/tjem.213.1] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Heme is a prosthetic group of various types of proteins, such as hemoglobin, myoglobin, cytochrome c, cytochrome p450, catalase and peroxidase. In addition, heme is involved in a variety of biological events by modulating the function or the state of hemoproteins. For example, protein synthesis is inhibited in erythroid cells under heme deficiency, as the consequence of the activation of heme-regulated inhibitor (HRI). Iron concentration in the cell is sensed and regulated by the heme-mediated oxidization and subsequent degradation of iron regulatory protein 2 (IRP2). Heme also binds to certain types of potassium channels, thereby inhibiting transmembrane K(+) currents. Importantly, heme determines its own fate; namely, heme regulates its synthesis and degradation through the feedback mechanisms, by which intracellular heme level is precisely maintained. Heme reduces heme synthesis by suppressing the expression of non-specific 5-aminolevulinate synthase (ALAS1) and stimulates heme breakdown by inducing heme oxygenase (HO)-1 expression. ALAS1 and HO-1 are the rate limiting enzymes in heme biosynthesis and catabolism, respectively. Accordingly, under the heme-rich condition, heme binds to cysteine-proline (CP) motifs of ALAS1 and those of transcriptional repressor Bach1, thereby leading to repression of mitochondrial transport of ALAS1 and induction of HO-1 transcription, respectively. Moreover, chemosensing functions of HO-2 containing CP motifs, another isozyme of HO, have been unveiled recently. In this review article, we summarize and update the pleiotropic effects of heme on various biological events and the regulatory network of heme biosynthesis and catabolism.
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Affiliation(s)
- Kazumichi Furuyama
- Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan.
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Miotto G, Tessaro S, Rotta GA, Bonatto D. In silico analyses of Fsf1 sequences, a new group of fungal proteins orthologous to the metazoan sideroblastic anemia-related sideroflexin family. Fungal Genet Biol 2006; 44:740-53. [PMID: 17240176 DOI: 10.1016/j.fgb.2006.12.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 11/16/2006] [Accepted: 12/11/2006] [Indexed: 02/01/2023]
Abstract
Sideroblastic anemias are pathologies observed in metazoan species characterized by accumulation of iron in the mitochondria (sideroblasts), defective erythropoiesis, and iron overload. Some genes have been associated with sideroblastic anemia, e.g. delta-aminolevulinic acid synthase gene (e-ALAS2). Recently, a new sideroblastic-associated protein family was discovered in metazoans and termed sideroflexin (Sfxn). The metazoan Sfxn family comprises five groups of paralogous proteins, present in mitochondria and whose functions are unknown. Using an in silico approach, we have identified and characterized new sideroflexin sequences from the genomes of different fungal species. An in-depth phylogenetic analysis of these new fungal Sfxn sequences (termed Fsf1p) showed that they form a distinct clade within the metazoan Sfxn family. Hydrophobic cluster analysis and transmembrane topological mapping allowed us to compare conserved regions among Fsf1 and Sfxn proteins. The results indicate that Fsf1 probably belongs to an ancient, mitochondrial group of proteins, necessary to maintain the homeostasis of iron within this organelle.
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Affiliation(s)
- Greice Miotto
- Instituto de Biotecnologia, Universidade de Caxias do Sul (UCS), Caxias do Sul, RS, Brazil
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Ajioka RS, Phillips JD, Kushner JP. Biosynthesis of heme in mammals. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:723-36. [PMID: 16839620 DOI: 10.1016/j.bbamcr.2006.05.005] [Citation(s) in RCA: 341] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Revised: 05/10/2006] [Accepted: 05/11/2006] [Indexed: 11/30/2022]
Abstract
Most iron in mammalian systems is routed to mitochondria to serve as a substrate for ferrochelatase. Ferrochelatase inserts iron into protoporphyrin IX to form heme which is incorporated into hemoglobin and cytochromes, the dominant hemoproteins in mammals. Tissue-specific regulatory features characterize the heme biosynthetic pathway. In erythroid cells, regulation is mediated by erythroid-specific transcription factors and the availability of iron as Fe/S clusters. In non-erythroid cells the pathway is regulated by heme-mediated feedback inhibition. All of the enzymes in the heme biosynthetic pathway have been crystallized and the crystal structures have permitted detailed analyses of enzyme mechanisms. All of the genes encoding the heme biosynthetic enzymes have been cloned and mutations of these genes are responsible for a group of human disorders designated the porphyrias and for X-linked sideroblastic anemia. The biochemistry, structural biology and the mechanisms of tissue-specific regulation are presented in this review along with the key features of the porphyric disorders.
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Affiliation(s)
- Richard S Ajioka
- Department of Internal Medicine, Division of Hematology, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
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Zhang J, Cheltsov AV, Ferreira GC. Conversion of 5-aminolevulinate synthase into a more active enzyme by linking the two subunits: spectroscopic and kinetic properties. Protein Sci 2005; 14:1190-200. [PMID: 15840827 PMCID: PMC2253255 DOI: 10.1110/ps.041258305] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The two active sites of dimeric 5-aminolevulinate synthase (ALAS), a pyridoxal 5'-phosphate (PLP)-dependent enzyme, are located on the subunit interface with contribution of essential amino acids from each subunit. Linking the two subunits into a single polypeptide chain dimer (2XALAS) yielded an enzyme with an approximate sevenfold greater turnover number than that of wild-type ALAS. Spectroscopic and kinetic properties of 2XALAS were investigated to explore the differences in the coenzyme structure and kinetic mechanism relative to those of wild-type ALAS that confer a more active enzyme. The absorption spectra of both ALAS and 2XALAS had maxima at 410 and 330 nm, with a greater A(410)/A(330) ratio at pH approximately 7.5 for 2XALAS. The 330 nm absorption band showed an intense fluorescence at 385 nm but not at 510 nm, indicating that the 330 nm absorption species is the substituted aldamine rather than the enolimine form of the Schiff base. The 385 nm emission intensity increased with increasing pH with a single pK of approximately 8.5 for both enzymes, and thus the 410 and 330 nm absorption species were attributed to the ketoenamine and substituted aldamine, respectively. Transient kinetic analysis of the formation and decay of the quinonoid intermediate EQ(2) indicated that, although their rates were similar in ALAS and 2XALAS, accumulation of this intermediate was greater in the 2XALAS-catalyzed reaction. Collectively, these results suggest that ketoenamine is the active form of the coenzyme and forms a more prominent coenzyme structure in 2XALAS than in ALAS at pH approximately 7.5.
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Affiliation(s)
- Junshun Zhang
- Department of Biochemistry and Molecular Biology, University of South Florida, Tampa 33612, USA
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15
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Cheltsov AV, Guida WC, Ferreira GC. Circular permutation of 5-aminolevulinate synthase: effect on folding, conformational stability, and structure. J Biol Chem 2003; 278:27945-55. [PMID: 12736261 DOI: 10.1074/jbc.m207011200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The first and regulatory step of heme biosynthesis in mammals begins with the pyridoxal 5'-phosphate-dependent condensation reaction catalyzed by 5-aminolevulinate synthase. The enzyme functions as a homodimer with the two active sites at the dimer interface. Previous studies demonstrated that circular permutation of 5-aminolevulinate synthase does not prevent folding of the polypeptide chain into a structure amenable to binding of the pyridoxal 5'-phosphate cofactor and assembly of the two subunits into a functional enzyme. However, while maintaining a wild type-like three-dimensional structure, active, circularly permuted 5-aminolevulinate synthase variants possess different topologies. To assess whether the aminolevulinate synthase overall structure can be reached through alternative or multiple folding pathways, we investigated the guanidine hydrochloride-induced unfolding, conformational stability, and structure of active, circularly permuted variants in relation to those of the wild type enzyme using fluorescence, circular dichroism, activity, and size exclusion chromatography. Aminolevulinate synthase and circularly permuted variants folded reversibly; the equilibrium unfolding/refolding profiles were biphasic and, in all but one case, protein concentration-independent, indicating a unimolecular process with the presence of at least one stable intermediate. The formation of this intermediate was preceded by the disruption of the dimeric interface or dissociation of the dimer without significant change in the secondary structural content of the subunits. In contrast to the similar stabilities associated with the dimeric interface, the energy for the unfolding of the intermediate as well as the overall conformational stabilities varied among aminolevulinate synthase and variants. The unfolding of one functional permuted variant was protein concentration-dependent and had a potentially different folding mechanism. We propose that the order of the ALAS secondary structure elements does not determine the ability of the polypeptide chain to fold but does affect its folding mechanism.
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Affiliation(s)
- Anton V Cheltsov
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612, USA
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16
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McLintock LA, Fitzsimons EJ. Erythroblast iron metabolism in sideroblastic and sideropenic states. ACTA ACUST UNITED AC 2003; 7:189-95. [PMID: 12243984 DOI: 10.1080/1024533021000013906] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Iron appears to exert self-regulatory control over erythroblast iron uptake, iron storage and its incorporation into haem. It does this via iron regulatory proteins (IRPs) which bind reversibly to the iron responsive elements (IREs) on the mRNA of transferrin receptor (TfR), erythroid 5-aminolaevulinic acid synthase (ALA-S2) and ferritin. Iron deficiency leads to the binding of IRP to IRE. This binding inhibits the translation of mRNA for ALA-S2 and ferritin but stabilizes mRNA for TfR expression. Sideroblastic erythropoiesis is highly ineffective and characterized by mitochondrial iron loading. The study of X-linked sideroblastic anaemia has shown that the entry of iron into the mitochondria is poorly controlled and able to occur when protoporphyrin production is reduced, as is seen with the ALA-S2 mutations, or when it is increased as has been seen with ABC7 transporter mutations. Sideropenia characterises both iron deficiency anaemia (IDA) and the anaemia of chronic disease (ACD). Erythroblasts in ACD seem doubly equipped to protect their iron supply with their ability to increase the efficiency of transferrin-iron uptake as well as to activate the IRP/IRE system to increase surface TfR production. This increase in efficiency restricts the need to increase surface TfR production and maintains serum soluble TfR (sTfR) values within the normal range in iron replete ACD. The coexistence of iron deficiency with chronic disease, however, is associated with an increase in both the efficiency and number and a highly significant rise in sTfR values.
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Affiliation(s)
- Lorna A McLintock
- University Department of Haematology, The Western Infirmary, Glasgow, UK
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17
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Zhang J, Ferreira GC. Transient state kinetic investigation of 5-aminolevulinate synthase reaction mechanism. J Biol Chem 2002; 277:44660-9. [PMID: 12191993 PMCID: PMC3733378 DOI: 10.1074/jbc.m203584200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
5-Aminolevulinate synthase (ALAS), a pyridoxal 5'-phosphate-dependent enzyme, catalyzes the first, and regulatory, step of the heme biosynthetic pathway in nonplant eukaryotes and some bacteria. 5-Aminolevulinate synthase is a dimeric protein having an ordered kinetic mechanism with glycine binding before succinyl-CoA and with aminolevulinate release after CoA and carbon dioxide. Rapid scanning stopped-flow absorption spectrophotometry in conjunction with multiple turnover chemical quenched-flow kinetic analyses and a newly developed CoA detection method were used to examine the ALAS catalytic reaction and identify the rate-determining step. The reaction of glycine with ALAS follows a three-step kinetic process, ascribed to the formation of the Michaelis complex and the pyridoxal 5'-phosphate-glycine aldimine, followed by the abstraction of the glycine pro-R proton from the external aldimine. Significantly, the rate associated with this third step (k(3) = 0.002 s(-1)) is consistent with the rate determined for the ALAS-catalyzed removal of tritium from [2-(3)H(2)]glycine. Succinyl-CoA and acetoacetyl-CoA increased the rate of glycine proton removal approximately 250,000- and 10-fold, respectively, supporting our previous proposal that the physiological substrate, succinyl-CoA, promotes a protein conformational change, which accelerates the conversion of the external aldimine into the initial quinonoid intermediate (Hunter, G. A., and Ferreira, G. C. (1999) J. Biol. Chem. 274, 12222-12228). Rapid scanning stopped-flow and quenched-flow kinetic analyses of the ALAS reaction under single turnover conditions lend evidence for two quinonoid reaction intermediates and a model of the ALAS kinetic mechanism in which product release is at least the partially rate-limiting step. Finally, the carbonyl and carboxylate groups of 5-aminolevulinate play a major protein-interacting role by inducing a conformational change in ALAS and, thus, possibly modulating product release.
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Affiliation(s)
- Junshun Zhang
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612
| | - Gloria C. Ferreira
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612
- Institute for Biomolecular Science, University of South Florida, Tampa, Florida 33612
- H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, Florida 33612
- To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612. Tel.: 813-974-5797; Fax: 813-974-0504;
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18
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Hurford MT, Marshall-Taylor C, Vicki SL, Zhou JZ, Silverman LM, Rezuke WN, Altman A, Tsongalis GJ. A novel mutation in exon 5 of the ALAS2 gene results in X-linked sideroblastic anemia. Clin Chim Acta 2002; 321:49-53. [PMID: 12031592 DOI: 10.1016/s0009-8981(02)00095-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
BACKGROUND Mutations in the erythroid-specific 5-aminolevulinate-synthase gene (ALAS2) have been identified in many cases of X-linked sideroblastic anemia (XLSA). METHODS A polymerase chain reaction-mediated restriction fragment length polymorphism (RFLP) assay was used. RESULTS A G527T point mutation was identified. This resulted in a substitution of tyrosine for asparagine at residue 159 (D159Y). This mutation was also identified in the mother of the two probands. Mutations in all three individuals were confirmed by DNA sequencing analysis. CONCLUSIONS We identified a missense mutation in exon 5 of the ALAS2 gene in two brothers of a consanguineous marriage, who were clinically pyridoxine-responsive.
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Affiliation(s)
- Matthew T Hurford
- Department of Pathology and Laboratory Medicine, Hartford Hospital, 80 Seymour Street, Hartford, CT 06102, USA
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19
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Affiliation(s)
- Thierry Alcindor
- Division of Haematology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
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20
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Goodfellow BJ, Dias JS, Ferreira GC, Henklein P, Wray V, Macedo AL. The solution structure and heme binding of the presequence of murine 5-aminolevulinate synthase. FEBS Lett 2001; 505:325-31. [PMID: 11566198 DOI: 10.1016/s0014-5793(01)02818-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mitochondrial import of 5-aminolevulinate synthase (ALAS), the first enzyme of the mammalian heme biosynthetic pathway, requires the N-terminal presequence. The 49 amino acid presequence transit peptide (psALAS) for murine erythroid ALAS was chemically synthesized, and circular dichroism and (1)H nuclear magnetic resonance (NMR) spectroscopies used to determine structural elements in trifluoroethanol/H(2)O solutions and micellar environments. A well defined amphipathic alpha-helix, spanning L22 to F33, was present in psALAS in 50% trifluoroethanol. Further, a short alpha-helix, defined by A5-L8, was also apparent in the 26 amino acid N-terminus peptide, when its structure was determined in sodium dodecyl sulfate. Heme inhibition of ALAS mitochondrial import has been reported to be mediated through cysteine residues in presequence heme regulatory motifs (HRMs). A UV/visible and (1)H NMR study of hemin and psALAS indicated that a heme-peptide interaction occurs and demonstrates, for the first time, that heme interacts with the HRMs of psALAS.
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Affiliation(s)
- B J Goodfellow
- Departamento de Quimica, Universidade de Aveiro, 3810-193 Aviero, Portugal
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21
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Cheltsov AV, Barber MJ, Ferreira GC. Circular permutation of 5-aminolevulinate synthase. Mapping the polypeptide chain to its function. J Biol Chem 2001; 276:19141-9. [PMID: 11279050 PMCID: PMC4547487 DOI: 10.1074/jbc.m100329200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
5-Aminolevulinate synthase is the first enzyme of the heme biosynthetic pathway in non-plant eukaryotes and some prokaryotes. The enzyme functions as a homodimer and requires pyridoxal 5'-phosphate as a cofactor. Although the roles of defined amino acids in the active site and catalytic mechanism have been recently explored using site-directed mutagenesis, much less is known about the role of the 5-aminolevulinate synthase polypeptide chain arrangement in folding, structure, and ultimately, function. To assess the importance of the continuity of the polypeptide chain, circularly permuted 5-aminolevulinate synthase variants were constructed through either rational design or screening of an engineered random library. One percent of the random library clones were active, and a total of 21 active variants had sequences different from that of the wild type 5-aminolevulinate synthase. Out of these 21 variants, 9 displayed unique circular permutations of the 5-aminolevulinate synthase polypeptide chain. The new termini of the active variants disrupted secondary structure elements and loop regions and fell in 100 amino acid regions from each terminus. This indicates that the natural continuity of the 5-aminolevulinate synthase polypeptide chain and the sequential arrangement of the secondary structure elements are not requirements for proper folding, binding of the cofactor, or assembly of the two subunits. Furthermore, the order of two identified functional elements (i.e. the catalytic and the glycine-binding domains) is apparently irrelevant for proper functioning of the enzyme. Although the wild type 5-aminolevulinate synthase and the circularly permuted variants appear to have similar, predicted overall tertiary structures, they exhibit differences in the arrangement of the secondary structure elements and in the cofactor-binding site environment. Taken together, the data lead us to propose that the 5-aminolevulinate synthase overall structure can be reached through multiple or alternative folding pathways.
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Affiliation(s)
- Anton V. Cheltsov
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612
| | - Michael J. Barber
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612
- Institute for Biomolecular Science, University of South Florida, Tampa, Florida 33612
| | - Gloria C. Ferreira
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa, Florida 33612
- Institute for Biomolecular Science, University of South Florida, Tampa, Florida 33612
- H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, Florida 33612
- To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612. Tel.: 813-974-5797; Fax: 813-974-0504;
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22
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Furuyama K, Sassa S. Interaction between succinyl CoA synthetase and the heme-biosynthetic enzyme ALAS-E is disrupted in sideroblastic anemia. J Clin Invest 2000; 105:757-64. [PMID: 10727444 PMCID: PMC377455 DOI: 10.1172/jci6816] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The first and the rate-limiting enzyme of heme biosynthesis is delta-aminolevulinate synthase (ALAS), which is localized in mitochondria. There are 2 tissue-specific isoforms of ALAS, erythroid-specific (ALAS-E) and nonspecific ALAS (ALAS-N). To identify possible mitochondrial factors that modulate ALAS-E function, we screened a human bone marrow cDNA library, using the mitochondrial form of human ALAS-E as a bait protein in the yeast 2-hybrid system. Our screening led to the isolation of the beta subunit of human ATP-specific succinyl CoA synthetase (SCS-betaA). Using transient expression and coimmunoprecipitation, we verified that mitochodrially expressed SCS-betaA associates specifically with ALAS-E and not with ALAS-N. Furthermore, the ALAS-E mutants R411C and M426V associated with SCS-betaA, but the D190V mutant did not. Because the D190V mutant was identified in a patient with pyridoxine-refractory X-linked sideroblastic anemia, our findings suggest that appropriate association of SCS-betaA and ALAS-E promotes efficient use of succinyl CoA by ALAS-E or helps translocate ALAS-E into mitochondria.
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Affiliation(s)
- K Furuyama
- Laboratory of Biochemical Hematology, The Rockefeller University, New York, New York 10021, USA
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23
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Aizencang GI, Bishop DF, Forrest D, Astrin KH, Desnick RJ. Uroporphyrinogen III synthase. An alternative promoter controls erythroid-specific expression in the murine gene. J Biol Chem 2000; 275:2295-304. [PMID: 10644678 DOI: 10.1074/jbc.275.4.2295] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Uroporphyrinogen III synthase (URO-synthase, EC 4.2.1.75) is the fourth enzyme of the heme biosynthetic pathway and is the defective enzyme in congenital erythropoietic porphyria. To investigate the erythroid-specific expression of murine URO-synthase, the cDNA and approximately 24-kilobase genomic sequences were isolated and characterized. Three alternative transcripts were identified containing different 5'-untranslated regions (5'-UTRs), but identical coding exons 2B through 10. Transcripts with 5'-UTR exon 1A alone or fused to exon 1B were ubiquitously expressed (housekeeping), whereas transcripts with 5'-UTR exon 2A were only present in erythroid cells (erythroid-specific). Analysis of the TATA-less housekeeping promoter upstream of exon 1A revealed binding sites for ubiquitously expressed transcription factors Sp1, NF1, AP1, Oct1, and NRF2. The TATA-less erythroid-specific promoter upstream of exon 2A had nine putative GATA1 erythroid enhancer binding sites. Luciferase promoter/reporter constructs transfected into NIH 3T3 and mouse erythroleukemia cells indicated that the housekeeping promoter was active in both cell lines, while the erythroid promoter was active only in erythroid cells. Site-specific mutagenesis of the first GATA1 binding site markedly reduced luciferase activity in K562 cells (<5% of wild type). Thus, housekeeping and erythroid-specific transcripts are expressed from alternative promoters of a single mouse URO-synthase gene.
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Affiliation(s)
- G I Aizencang
- Department of Human Genetics, Mount Sinai School of Medicine, New York, New York 10029, USA
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24
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Four New Mutations in the Erythroid-Specific 5-Aminolevulinate Synthase (ALAS2) Gene Causing X-Linked Sideroblastic Anemia: Increased Pyridoxine Responsiveness After Removal of Iron Overload by Phlebotomy and Coinheritance of Hereditary Hemochromatosis. Blood 1999. [DOI: 10.1182/blood.v93.5.1757.405a12_1757_1769] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
X-linked sideroblastic anemia (XLSA) in four unrelated male probands was caused by missense mutations in the erythroid-specific 5-aminolevulinate synthase gene (ALAS2). All were new mutations: T647C, C1283T, G1395A, and C1406T predicting amino acid substitutions Y199H, R411C, R448Q, and R452C. All probands were clinically pyridoxine-responsive. The mutation Y199H was shown to be the first de novo XLSA mutation and occurred in a gamete of the proband’s maternal grandfather. There was a significantly higher frequency of coinheritance of the hereditary hemochromatosis (HH)HFE mutant allele C282Y in 18 unrelated XLSA hemizygotes than found in the normal population, indicating a role for coinheritance ofHFE alleles in the expression of this disorder. One proband (Y199H) with severe and early iron loading coinherited HH as a C282Y homozygote. The clinical and hematologic histories of two XLSA probands suggest that iron overload suppresses pyridoxine responsiveness. Notably, reversal of the iron overload in the Y199H proband by phlebotomy resulted in higher hemoglobin concentrations during pyridoxine supplementation. The proband with the R452C mutation was symptom-free on occasional phlebotomy and daily pyridoxine. These studies indicate the value of combined phlebotomy and pyridoxine supplementation in the management of XLSA probands in order to prevent a downward spiral of iron toxicity and refractory anemia.
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25
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Four New Mutations in the Erythroid-Specific 5-Aminolevulinate Synthase (ALAS2) Gene Causing X-Linked Sideroblastic Anemia: Increased Pyridoxine Responsiveness After Removal of Iron Overload by Phlebotomy and Coinheritance of Hereditary Hemochromatosis. Blood 1999. [DOI: 10.1182/blood.v93.5.1757] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
X-linked sideroblastic anemia (XLSA) in four unrelated male probands was caused by missense mutations in the erythroid-specific 5-aminolevulinate synthase gene (ALAS2). All were new mutations: T647C, C1283T, G1395A, and C1406T predicting amino acid substitutions Y199H, R411C, R448Q, and R452C. All probands were clinically pyridoxine-responsive. The mutation Y199H was shown to be the first de novo XLSA mutation and occurred in a gamete of the proband’s maternal grandfather. There was a significantly higher frequency of coinheritance of the hereditary hemochromatosis (HH)HFE mutant allele C282Y in 18 unrelated XLSA hemizygotes than found in the normal population, indicating a role for coinheritance ofHFE alleles in the expression of this disorder. One proband (Y199H) with severe and early iron loading coinherited HH as a C282Y homozygote. The clinical and hematologic histories of two XLSA probands suggest that iron overload suppresses pyridoxine responsiveness. Notably, reversal of the iron overload in the Y199H proband by phlebotomy resulted in higher hemoglobin concentrations during pyridoxine supplementation. The proband with the R452C mutation was symptom-free on occasional phlebotomy and daily pyridoxine. These studies indicate the value of combined phlebotomy and pyridoxine supplementation in the management of XLSA probands in order to prevent a downward spiral of iron toxicity and refractory anemia.
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26
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Yin X, Dailey HA. Erythroid 5-aminolevulinate synthase is required for erythroid differentiation in mouse embryonic stem cells. Blood Cells Mol Dis 1998; 24:41-53. [PMID: 9516380 DOI: 10.1006/bcmd.1998.0169] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have examined the induction of the enzymes of the heme biosynthetic pathway during erythroid differentiation of mouse embryonic stem (ES) cells. Following transfer to appropriate medium all of the pathway enzymes are induced within three days. Unlike differentiating mouse erythroleukemia cells (Lake-Bullock, H. and Dailey, H.A. Mol Cell Biol 13:7122-7132, 1993), all of the enzymes appear to be induced simultaneously and not sequentially in differentiating ES cells. The role of erythroid 5-aminolevulinate synthase (ALAS-2) in this differentiation process was examined by disruption of the ALAS-2 gene. The targeting vector used for disruption replaced all of exons 4 to 6 with a selectable neomycin resistance gene. The resulting genetically modified (ALAS-2 knockout) cells, as well as normal ES cells were used to study induction of heme biosynthesis. Following 10 days of culture in methylcellulose media significant morphological differences between the embryoid bodies (EBs) of the two cell lines were observed. ES cells exhibited morphology of typical EBs with a dark field (blood island) in the center, while ALAS-2 knockout ES cells developed very poorly both in size and shape. At 8 days of differentiation, only 3% of all EBs contained visible erythropoietic cells (i.e., stained positively for hemoglobin) in the ALAS-2 knockout cell line, compared with 50% in ES cells. Most of the genes in the heme synthetic pathway were expressed to a stable level within 3 to 6 days after induction in normal ES cells, while the ALAS-2 knockout cell line failed to significantly increase the level of expression of these genes. Fetal beta-globin mRNA was not detectable in the differentiating ALAS-2 knockout cells, whereas mRNA for this gene was detected in normal ES cells within 3 days of differentiation. These results suggest that ALAS-2 is necessary for ES cell erythroid differentiation and that there is an interrelationship between heme and globin synthesis in differentiating ES cells.
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Affiliation(s)
- X Yin
- Department of Biochemisty and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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27
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Edgar AJ, Wickramasinghe SN. Hereditary sideroblastic anaemia due to a mutation in exon 10 of the erythroid 5-aminolaevulinate synthase gene. Br J Haematol 1998; 100:389-92. [PMID: 9488633 DOI: 10.1046/j.1365-2141.1998.00569.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
DNA sequencing of the coding region of the erythroid 5-aminolaevulinate synthase (ALAS2) cDNA from a male with pyridoxine-responsive sideroblastic anaemia revealed a missense mutation C1622G and a closely linked polymorphism C1612A in exon 10 of the gene. Sequence analysis of the genomic DNA from other family members revealed that the proband's mother and daughter were heterozygous carriers of the mutation, consistent with the X-linked inheritance. The C1622G mutation results in a histidine to aspartic acid substitution at amino acid residue 524. The histidine residue is conserved in both the erythroid and housekeeping ALAS proteins in vertebrates, all other known ALAS proteins and other oxamine synthases that have pyridoxal 5'-phosphate as a co-factor. This histidine is located in a predicted loop, preceding a long alpha-helix region near the carboxy-terminus.
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Affiliation(s)
- A J Edgar
- Department of Haematology, Imperial College School of Medicine, St Mary's Hospital, London
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28
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Abstract
Two of the major organs producing heme are bone marrow and the liver. delta-Aminolevulinate synthase (ALAS) plays the key role to regulate heme biosynthesis in hepatocytes as well as in erythroid cells. In the liver, nonspecific (or housekeeping) isozyme of ALAS (ALAS-N) is expressed to be regulated by its end product, heme, in a negative feedback manner. The way to regulate ALAS-N in the liver is suitable to supply a constant level of heme for a family of drug metabolizing enzymes, cytochrome P-450 (CYP). In erythroid tissues, not only erythroid-specific isozyme of ALAS (ALAS-E) but also ALAS-N are expressed, and regulated by distinctive manners. Although heme regulates ALAS-N in a negative feedback manner even in erythroid cells, ALAS-E is upregulated by induced heme concentration. ALAS-N in undifferentiated erythroid cells, therefore, is suggested to produce heme for CYP, whereas heme for accumulating hemoglobin (Hb) in cells undergoing differentiation is synthesized via ALAS-E. In this article, we describe the molecular mechanisms to regulate heme biosynthesis in non-erythroid as well as in erythroid tissues, and discuss the pathological significance of the mechanisms in patients with inherited disorders, porphyrias.
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Affiliation(s)
- H Fujita
- Department of Molecular Biology & Applied Physiology, Tohoku University School of Medicine, Sendai
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29
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Pyridoxine Refractory X-Linked Sideroblastic Anemia Caused by a Point Mutation in the Erythroid 5-Aminolevulinate Synthase Gene. Blood 1997. [DOI: 10.1182/blood.v90.2.822] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractTo elucidate how pyridoxine-refractory X-linked sideroblastic anemia (XLSA) develops, we analyzed the erythroid-specific 5-aminolevulinate synthase (ALAS-E) gene of a patient with the anemia. The activity and amount of the enzyme in bone marrow cells of the patient were found to be approximately 5% of the normal control. We identified a point mutation, which introduces an amino acid substitution from Asp 190 to Val. In transient transfection analyses using quail fibroblasts, accumulation of aberrantly processed proteins, the sizes of which were larger than that of mature ALAS-E, was found in mitochondria. The proteins were reproducibly detected in assays combining in vitro transcription/translation of ALAS-E precursor and import of the precursor into isolated mouse mitochondria. These results suggest that the mutation causing pyridoxine-refractory XLSA affects the processing of the ALAS-E precursor, thus provoking instability of the ALAS-E protein.
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30
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Pyridoxine Refractory X-Linked Sideroblastic Anemia Caused by a Point Mutation in the Erythroid 5-Aminolevulinate Synthase Gene. Blood 1997. [DOI: 10.1182/blood.v90.2.822.822_822_830] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
To elucidate how pyridoxine-refractory X-linked sideroblastic anemia (XLSA) develops, we analyzed the erythroid-specific 5-aminolevulinate synthase (ALAS-E) gene of a patient with the anemia. The activity and amount of the enzyme in bone marrow cells of the patient were found to be approximately 5% of the normal control. We identified a point mutation, which introduces an amino acid substitution from Asp 190 to Val. In transient transfection analyses using quail fibroblasts, accumulation of aberrantly processed proteins, the sizes of which were larger than that of mature ALAS-E, was found in mitochondria. The proteins were reproducibly detected in assays combining in vitro transcription/translation of ALAS-E precursor and import of the precursor into isolated mouse mitochondria. These results suggest that the mutation causing pyridoxine-refractory XLSA affects the processing of the ALAS-E precursor, thus provoking instability of the ALAS-E protein.
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31
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Batra RS, Hatchwell E, Rider S, Brown R, Brown GK, Craig IW. Localization of human liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB1) within a YAC contig in Xp11.21. Genomics 1997; 40:358-61. [PMID: 9119406 DOI: 10.1006/geno.1996.4530] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) catalyzes the synthesis and degradation of fructose-2,6-bisphosphate, a potent regulator of glycolysis. Previous studies assigned the gene for human liver PFK-2/FBPase-2 (HGMW-approved symbol PFKFB1) to the X chromosome; however, precise localization remained ambiguous, with the gene variously placed between Xcen-q13, Xq27-q28, and Xp11.22-p11.21. We have localized the gene within a YAC contig clustered around ALAS2 (human erythroid delta-aminolevulinate synthase) in Xp11.21 and have identified eight YACs positive for the gene. Four of these overlapping YACs were mapped using rare-cutter restriction enzymes to provide in-depth characterization of an 820-kb region encompassing the PFK-2/ FBPase-2 and ALAS2 genes. PFK-2/FBPase-2 was found to lie close (within approx. 250 kb) and telomeric to ALAS2. Three putative CpG islands were also detected in the region.
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Affiliation(s)
- R S Batra
- Department of Biochemistry, University of Oxford, United Kingdom
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32
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Tissue-Specific Regulation of Iron Metabolism and Heme Synthesis: Distinct Control Mechanisms in Erythroid Cells. Blood 1997. [DOI: 10.1182/blood.v89.1.1] [Citation(s) in RCA: 393] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Abstract
We have described a procedure for production and purification of recombinant, mature-length mouse ALAS-2. The fact that E. coli utilizes the C5 path for ALA production means that there is no problem with contamination of the recombinant ALAS-2 by host cell enzyme, such as one may have with a yeast expression system. While the detailed procedure produces enzyme in good yield with relatively common protein purification techniques, future expression systems may be developed to take advantage of the rapid purification achieved by the use of a 6-histidine (His6) aminoterminal tag and metal chelate chromatography. Such approaches in this laboratory with protoporphyrinogen oxidase, coproporphyrinogen oxidase, and uroporphyrinogen decarboxylase have resulted in the production and purification of enzymes whose kinetic and physical parameters are essentially identical to those of proteins lacking the His6 tag.
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Affiliation(s)
- H A Dailey
- Department of Microbiology, University of Georgia, Athens 30602-7229, USA
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34
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Edgar AJ, Losowsky MS, Noble JS, Wickramasinghe SN. Identification of an arginine452 to histidine substitution in the erythroid 5-aminolaevulinate synthetase gene in a large pedigree with X-linked hereditary sideroblastic anaemia. Eur J Haematol Suppl 1997; 58:1-4. [PMID: 9020366 DOI: 10.1111/j.1600-0609.1997.tb01402.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The coding region of the erythroid 5-aminolaevulinate synthetase gene (ALAS2) from a large pedigree with pyridoxine-responsive X-linked hereditary sideroblastic anaemia was examined for mutations. In three affected males from this pedigree, single strand conformational polymorphism (SSCP) analysis showed anomalous migration of a PCR product spanning exon 9. Sequencing of amplified genomic DNA from one of these affected males revealed a guanine to adenine transition at nucleotide 1407 of the cDNA sequence in exon 9 of the gene. This mutation results in the loss of an HhaI restriction enzyme digest site. An HhaI digest assay demonstrated the presence of this mutation in other affected males but not in unaffected males and unrelated individuals. The point mutation results in an arginine to histidine substitution at amino acid residue 452. The arginine residue is conserved in both the erythroid and housekeeping ALAS genes in all known vertebrate sequences. This arginine is located in the middle of a predicted alpha-helix.
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Affiliation(s)
- A J Edgar
- Department of Haematology, Imperial College of Medicine at St Mary's, London, UK
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35
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Tissue-Specific Regulation of Iron Metabolism and Heme Synthesis: Distinct Control Mechanisms in Erythroid Cells. Blood 1997. [DOI: 10.1182/blood.v89.1.1.1_1_25] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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36
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Noble JS, Taylor GR, Losowsky MS, Hall R, Turner G, Mueller RF, Stewart AD. Linkage analysis of a large pedigree with hereditary sideroblastic anaemia. J Med Genet 1995; 32:389-92. [PMID: 7616548 PMCID: PMC1050436 DOI: 10.1136/jmg.32.5.389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A large pedigree showing a history of pyridoxine responsive X linked sideroblastic anaemia was screened with several polymorphic DNA markers from the X chromosome. Linkage analysis between each marker and disease status was performed, giving a maximum two point lod score of 3.64 at zero recombination with the microsatellite marker PGK1P1 at Xq11.2-12. Close linkage to PGK at Xq13.3, one of the candidate regions for X linked sideroblastic anaemia, was excluded. Linkage to DNA markers distal to PGK and at Xp21 was also excluded. Multipoint linkage analysis was performed with markers located between Xq11.2-21. The maximum map specific lod score obtained was 3.56 at PGK1P1 (Xq11.2-12). Linkage remained significant over the interval 20 cM proximal to PGK1P1 and 5 cM distal to PGK1P1, with definite exclusion around the PGK locus. The most likely location of the gene involved in sideroblastic anaemia in this pedigree is therefore within the pericentromeric region of the X chromosome. This region includes the erythroid 5-aminolaevulinate synthetase gene of the haem synthesis pathway, which is a candidate gene for X linked sideroblastic anaemia located at Xp11.21.
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Affiliation(s)
- J S Noble
- Yorkshire Regional Genetics Service, St James's University Hospital, Leeds, UK
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37
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Bottomley SS, May BK, Cox TC, Cotter PD, Bishop DF. Molecular defects of erythroid 5-aminolevulinate synthase in X-linked sideroblastic anemia. J Bioenerg Biomembr 1995; 27:161-8. [PMID: 7592563 DOI: 10.1007/bf02110031] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The erythroid-specific isozyme of 5-aminolevulinate synthase (ALAS2), the first and rate-limiting enzyme of heme biosynthesis, is expressed concomitantly with the differentiation and maturation of the erythroid cell in order to accommodate generation of the large amounts of heme required for hemoglobin production. During the past few years the ALAS2 gene and its transcript have been characterized and the amino acid sequence of the enzyme deduced. The human genetic disorder X-linked sideroblastic anemia, previously postulated to be caused by defects of ALAS, has now been analyzed at the molecular and tissue-specific level. A heterogeneous group of point mutations in the catalytic domain of the ALAS2 enzyme has been found to cause the disorder. Impaired activity of recombinant mutant ALAS2 enzymes has also been demonstrated. Characterization of molecular defects in individuals with X-linked sideroblastic anemia has provided improved diagnosis for at-risk family members.
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Affiliation(s)
- S S Bottomley
- Department of Medicine, University of Oklahoma College of Medicine, Oklahoma City 73104, USA
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38
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de Kok YJ, van der Maarel SM, Bitner-Glindzicz M, Huber I, Monaco AP, Malcolm S, Pembrey ME, Ropers HH, Cremers FP. Association between X-linked mixed deafness and mutations in the POU domain gene POU3F4. Science 1995; 267:685-8. [PMID: 7839145 DOI: 10.1126/science.7839145] [Citation(s) in RCA: 279] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Deafness with fixation of the stapes (DFN3) is the most frequent X-linked form of hearing impairment. The underlying gene has been localized to a 500-kilobase segment of the Xq21 band. Here, it is reported that a candidate gene for this disorder, Brain 4 (POU3F4), which encodes a transcription factor with a POU domain, maps to the same interval. In five unrelated patients with DFN3 but not in 50 normal controls, small mutations were found that result in truncation of the predicted protein or in nonconservative amino acid substitutions. These findings indicate that POU3F4 mutations are a molecular cause of DFN3.
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Affiliation(s)
- Y J de Kok
- Department of Human Genetics, University Hospital Nijmegen, Netherlands
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39
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Abstract
The startling morphological abnormalities of sideroblastic anaemia contrasts our uncertainty about its cause. Studies are hampered by the fact that the abnormality resides in the dividing and differentiating erythroblast which is difficult to obtain pure and in large numbers, and in which many levels of metabolic control must coexist. Recent molecular biology approaches have confirmed abnormalities of erythroid delta-aminolaevulinic acid synthase as the cause of X-linked, pyridoxine-responsive sideroblastic anaemia and mitochondrial DNA deletions as the most common cause of congenital macrocytic sideroblastic anaemia. They have also identified a second X-linked sideroblastic anaemia locus linked to phosphoglycerate kinase and associated with ataxia. An association between sideroblastic anaemia and the use of an oral copper chelating agent has highlighted unexplained links between erythroid copper and iron metabolism. Management decisions in relation to pyridoxine treatment, iron reduction, family studies, genetic counselling and antenatal diagnosis have in recent years become of practical relevance to families with known cases of congenital sideroblastic anaemia and careful documentation of the clinical outcome of these cases and of other family members is invaluable. Parallel and integrated studies on the molecular biology of erythroid differentiation are revealing the range of possible controlling influences on erythroblasts and defining the circumstances for each, allowing studies on the cause of the most prevalent form of sideroblastic anaemia (the idiopathic acquired form) and those inherited forms that are not X-linked to be approached with a much clearer perspective.
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Affiliation(s)
- A May
- University of Wales College of Medicine, Cardiff, UK
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40
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Chapman VM, Keitz BT, Bishop DF. Genetic linkage of the erythroid-specific delta-aminolevulinate synthase gene (Alas2) to the distal region of the mouse X chromosome. Mamm Genome 1994; 5:741. [PMID: 7873890 DOI: 10.1007/bf00426087] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- V M Chapman
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263
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41
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42
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Jardine PE, Cotter PD, Johnson SA, Fitzsimons EJ, Tyfield L, Lunt PW, Bishop DF. Pyridoxine-refractory congenital sideroblastic anaemia with evidence for autosomal inheritance: exclusion of linkage to ALAS2 at Xp11.21 by polymorphism analysis. J Med Genet 1994; 31:213-8. [PMID: 7912287 PMCID: PMC1049745 DOI: 10.1136/jmg.31.3.213] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A son and daughter of unaffected parents had transfusion dependent, pyridoxine-refractory sideroblastic anaemia from birth. Their haemoglobin levels were 4.3 and 6.4 g/dl, respectively. delta-Aminolaevulinate synthase activity in erythroblasts from fractionated marrow of the sister was 135 pmol delta-aminolaevulinate formed/10(6) erythroblasts/hour (normal range = 110-650 pmol). While mutations of the erythroid-specific delta-aminolaevulinate synthase gene (ALAS2) at Xp11.21 have been reported in patients with X linked sideroblastic anaemia, sequence analysis of the ALAS2 gene in the son did not identify any mutations in the coding region, the intron/exon boundaries, or the 1 kb 5' promoter region. A useful polymorphism was found in the 3' region of the ALAS2 gene, a G to A transition, 220 nt 3' of the AATAAA polyadenylation signal. Mismatch PCR at this site and subsequent discrimination by XmnI restriction analysis of 148 alleles identified the gene frequency of this polymorphism to be 25%. Analysis of the inheritance of this intragenic polymorphism showed that the affected sibs received different maternal alleles at the ALAS2 locus, excluding mutations in this gene as the cause of their sideroblastic anaemia. Furthermore, the absence of a dimorphic erythrocyte population in the mother, coupled with the demonstration of random X inactivation in her peripheral leucocytes, showed that the mother was not the carrier of any X linked sideroblastic anaemia mutation. These results strongly suggest that the sideroblastic anaemia in this family is an autosomal recessive trait.
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Affiliation(s)
- P E Jardine
- Department of Clinical Genetics, Institute of Child Health, St Michaels Hill, Bristol, UK
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43
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Yamamoto M, Lim K, Nagai T, Furuyama K, Engel JD. Structure and regulation of vertebrate δ‐aminolevulinate synthases. Stem Cells 1994. [DOI: 10.1002/stem.5530120705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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44
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Abstract
1. The porphyrias are a group of metabolic disorders arising from defects in the haem biosynthetic pathway. Most forms are inherited as Mendelian autosomal dominants, but some types are recessive and others acquired through exposure to porphyrinogenic drugs and chemicals. There is a linked group of diseases, which are not porphyrias, but have in common alterations of haem biosynthesis. 2. The processes of haem biosynthesis are now well understood and the molecular biology of the functions and dysfunctions in the porphyrias are currently an area of intensive investigation. 3. The acute porphyrias, Acute Intermittent Porphyria, Variegate Porphyria and Hereditary Coproporphyria are of most importance since attacks of these may be life-threatening. 4. These diseases that usually present with a neurovisceral attack are characterized by excess production of the porphyrin precursors, 5-aminolaevulinate and porphobilinogen because of lowered activity of Porphobilinogen deaminase. 5. A variety of factors may precipitate these attacks including various drugs, alcohol, smoking, dieting or fasting and variations in steroid hormone levels. 6. The non-acute porphyrias are largely dermatological conditions, which present clinically as cutaneous photosensitivity. The dermatological changes are caused by the photosensitizing properties of circulating porphyrins and are accompanied by systemic effects of these porphyrins.
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Affiliation(s)
- M R Moore
- University of Glasgow, Department of Medicine and Therapeutics, Western Infirmary, Scotland
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45
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Gorski JL, Boehnke M, Reyner EL, Burright EN. A radiation hybrid map of the proximal short arm of the human X chromosome spanning incontinentia pigmenti 1 (IP1) translocation breakpoints. Genomics 1992; 14:657-65. [PMID: 1427892 DOI: 10.1016/s0888-7543(05)80165-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Radiation hybrid mapping was used in combination with physical mapping techniques to order and estimate distances between 14 loci in the proximal region of the short arm of the human X chromosome. A panel of radiation hybrids containing human X-chromosomal fragments was generated from a Chinese hamster-human cell hybrid containing an X chromosome as its only human DNA. Sixty-seven radiation hybrids were screened by Southern hybridization with sets of probes that mapped to the region Xp11.4-Xcen to generate a radiation hybrid map of the area. A physical map of 14 loci was constructed based on the segregation of the loci in the hybrid clones. Using pulsed-field gel electrophoresis (PFGE) analyses and a somatic cell hybrid mapping panel containing naturally occurring X; autosome translocations, the order of the 14 loci was verified and the loci nearest to the X-chromosomal translocation breakpoints associated with the disease incontinentia pigmenti 1 (IP1) were identified. The radiation hybrid panel will be useful as a mapping resource for determining the location, order, and distances between other genes and polymorphic loci in this region as well as for generating additional region-specific DNA markers.
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Affiliation(s)
- J L Gorski
- Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor 48109-0688
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46
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Gorski JL, Burright EN, Reyner EL, Goodfellow PN, Burgess DL. Isolation of DNA markers from a region between incontinentia pigmenti 1 (IP1) X-chromosomal translocation breakpoints by a comparative PCR analysis of a radiation hybrid subclone mapping panel. Genomics 1992; 14:649-56. [PMID: 1427891 DOI: 10.1016/s0888-7543(05)80164-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A strategy based on the use of human-specific interspersed repetitive sequence (IRS)-PCR amplification was used to isolate regional DNA markers in the vicinity of the incontinentia pigmenti 1 (IP1) locus. A radiation hybrid (RH) resulting from a fusion of an irradiated X-only somatic cell hybrid (C12D) and a thymidine kinase deficient (TK-) hamster cell line (a23) was identified as containing multiple X chromosome fragments, including DNA markers spanning IP1 X-chromosomal translocation breakpoints within region Xp11.21. From this RH, a panel of subclones was constructed and analyzed by IRS-PCR amplification to (a) identify subclones containing a reduced number of X chromosome fragments spanning the IP1 breakpoints and (b) construct a mapping panel to assist in identifying regional DNA markers in the vicinity of the IP1 locus. By using this strategy, we have isolated three different IRS-PCR amplification products that map to a region between IP1 X chromosome translocation breakpoints. A total of nine DNA sequences have now been mapped to this region; using these DNA markers for PFGE analyses, we obtained a probe order DXS14-DXS422-MTHFDL1-DXS705. These DNA markers provide a starting point for identifying overlapping genomic sequences spanning the IP1 translocation breakpoints; the availability of IP1 translocation breakpoints should assist the molecular analysis of this locus.
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Affiliation(s)
- J L Gorski
- Department of Pediatrics, University of Michigan, Ann Arbor 48109
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