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Rosenfeld JA, Xiao R, Bekheirnia MR, Kanani F, Parker MJ, Koenig MK, van Haeringen A, Ruivenkamp C, Rosmaninho-Salgado J, Almeida PM, Sá J, Basto JP, Palen E, Oetjens KF, Burrage LC, Xia F, Liu P, Eng CM, Yang Y, Posey JE, Lee BH. Heterozygous variants in SPTBN1 cause intellectual disability and autism. Am J Med Genet A 2021; 185:2037-2045. [PMID: 33847457 PMCID: PMC11182376 DOI: 10.1002/ajmg.a.62201] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 02/26/2021] [Accepted: 03/24/2021] [Indexed: 11/09/2022]
Abstract
Spectrins are common components of cytoskeletons, binding to cytoskeletal elements and the plasma membrane, allowing proper localization of essential membrane proteins, signal transduction, and cellular scaffolding. Spectrins are assembled from α and β subunits, encoded by SPTA1 and SPTAN1 (α) and SPTB, SPTBN1, SPTBN2, SPTBN4, and SPTBN5 (β). Pathogenic variants in various spectrin genes are associated with erythroid cell disorders (SPTA1, SPTB) and neurologic disorders (SPTAN1, SPTBN2, and SPTBN4), but no phenotypes have been definitively associated with variants in SPTBN1 or SPTBN5. Through exome sequencing and case matching, we identified seven unrelated individuals with heterozygous SPTBN1 variants: two with de novo missense variants and five with predicted loss-of-function variants (found to be de novo in two, while one was inherited from a mother with a history of learning disabilities). Common features include global developmental delays, intellectual disability, and behavioral disturbances. Autistic features (4/6) and epilepsy (2/7) or abnormal electroencephalogram without overt seizures (1/7) were present in a subset. Identification of loss-of-function variants suggests a haploinsufficiency mechanism, but additional functional studies are required to fully elucidate disease pathogenesis. Our findings support the essential roles of SPTBN1 in human neurodevelopment and expand the knowledge of human spectrinopathy disorders.
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Affiliation(s)
- Jill A. Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
| | - Rui Xiao
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
- Baylor Genetics Laboratories, Houston, Texas, 77030, USA
| | - Mir Reza Bekheirnia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
- Renal Section, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, 77030, USA
| | - Farah Kanani
- Sheffield Clinical Genetics Service, Sheffield Children's NHS Foundation Trust, Sheffield, UK
| | - Michael J. Parker
- The Wellcome Centre for Ethics and Humanities/Ethox Centre, Nuffield Department of Population Health, University of Oxford, Oxford, UK
| | - Mary K. Koenig
- Department of Pediatrics, University of Texas Health Science Center, Houston, Texas, 77030, USA
| | - Arie van Haeringen
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
| | - Claudia Ruivenkamp
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, Netherlands
| | - Joana Rosmaninho-Salgado
- Medical Genetics Unit, Hospital Pediátrico, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | - Pedro M. Almeida
- Medical Genetics Unit, Hospital Pediátrico, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | - Joaquim Sá
- Medical Genetics Unit, Hospital Pediátrico, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | - Jorge Pinto Basto
- Molecular Diagnostics and Clinical Genomics, CGC Genetics, Porto, Portugal
| | - Emily Palen
- Autism & Developmental Medicine Institute, Geisinger, Danville, Pennsylvania, 17822, USA
| | - Kathryn F. Oetjens
- Autism & Developmental Medicine Institute, Geisinger, Danville, Pennsylvania, 17822, USA
| | - Lindsay C. Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
- Texas Children’s Hospital, Houston, Texas, 77030, USA
| | - Fan Xia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
- Baylor Genetics Laboratories, Houston, Texas, 77030, USA
| | - Pengfei Liu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
- Baylor Genetics Laboratories, Houston, Texas, 77030, USA
| | - Christine M. Eng
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
- Baylor Genetics Laboratories, Houston, Texas, 77030, USA
| | | | - Yaping Yang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
- Baylor Genetics Laboratories, Houston, Texas, 77030, USA
| | - Jennifer E. Posey
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
| | - Brendan H. Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
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2
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Meng LL, Yuan SM, Tu CF, Lin G, Lu GX, Tan YQ. Next-generation sequencing identified a novel SPTB frameshift insertion causing hereditary spherocytosis in China. Ann Hematol 2018; 98:223-226. [PMID: 29961904 DOI: 10.1007/s00277-018-3417-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 06/24/2018] [Indexed: 10/28/2022]
Affiliation(s)
- Lan-Lan Meng
- Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine, Central South University, Changsha, 410078, Hunan, People's Republic of China.,Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, Hunan, People's Republic of China
| | - Shi-Min Yuan
- Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine, Central South University, Changsha, 410078, Hunan, People's Republic of China.,Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, Hunan, People's Republic of China
| | - Chao-Feng Tu
- Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine, Central South University, Changsha, 410078, Hunan, People's Republic of China.,Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, Hunan, People's Republic of China
| | - Ge Lin
- Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine, Central South University, Changsha, 410078, Hunan, People's Republic of China.,Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, Hunan, People's Republic of China
| | - Guang-Xiu Lu
- Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine, Central South University, Changsha, 410078, Hunan, People's Republic of China.,Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, Hunan, People's Republic of China
| | - Yue-Qiu Tan
- Institute of Reproduction and Stem Cell Engineering, School of Basic Medicine, Central South University, Changsha, 410078, Hunan, People's Republic of China. .,Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, Hunan, People's Republic of China.
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3
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Ma S, Qin J, Wei A, Li X, Qin Y, Liao L, Lin F. Novel compound heterozygous SPTA1 mutations in a patient with hereditary elliptocytosis. Mol Med Rep 2018; 17:5903-5911. [PMID: 29484404 PMCID: PMC5866036 DOI: 10.3892/mmr.2018.8632] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 01/24/2018] [Indexed: 12/19/2022] Open
Abstract
Hereditaryelliptocytosis (HE) is a hereditary hemolytic disease, characterized by the presence of many elliptical erythrocytes in the peripheral blood that is caused by abnormal cytoskeletal proteins in the erythrocyte membrane. In the present study, a novel, causal HE mutation was reported. Routine blood examinations were performed on the proband and their family, and the fluorescence intensity of eosin‑5‑maleimide (EMA)‑labeled erythrocytes was determined via flow cytometry. Subsequently, DNA was extracted from the peripheral blood of the proband and their family members, and amplified by quantitative polymerase chain reaction. The Sanger sequencing approach was used to determine and identify gene mutations, which were verified by matrix‑assisted laser desorption‑ionization time of flight (MALDI‑TOF) mass spectrometry. To exclude genetic polymorphisms, newly identified mutations were subjected to large‑scale gene screening using high‑resolution melt analysis. Protein expression levels in the erythrocyte membrane of the proband were determined via SDS‑PAGE, which demonstrated that, compared with healthy controls, the proband exhibited a reduction in EMA‑labeled erythrocytes. In addition, DNA analysis demonstrated that the proband carried three mutations in the spectrin α chain erythrocytic 1 (SPTA1) gene: c.161A>C, c.5572C>G and 6531‑12C>T. The corresponding mutant polypeptides were also analyzed by MALDI‑TOF mass spectroscopy. SDS‑PAGE analysis indicated that the proband exhibited normal levels of erythrocyte membrane proteins. In the present study, a novel HE case with a His54Pro mutation in the SPTA1 gene was reported. The results suggested that the His54Pro mutation influenced the role of erythrocyte membrane proteins without reducing its level of expression.
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Affiliation(s)
- Shiyue Ma
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, P.R. China
| | - Jinqiu Qin
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, P.R. China
| | - Aiqiu Wei
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, P.R. China
| | - Xiaohong Li
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, P.R. China
| | - Yuanyuan Qin
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, P.R. China
| | - Lin Liao
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, P.R. China
| | - Faquan Lin
- Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, P.R. China
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4
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Exome sequencing confirms molecular diagnoses in 38 Chinese families with hereditary spherocytosis. SCIENCE CHINA-LIFE SCIENCES 2018; 61:947-953. [PMID: 29572776 DOI: 10.1007/s11427-017-9232-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 12/28/2017] [Indexed: 12/24/2022]
Abstract
Hereditary spherocytosis (HS), the most common cause of congenital hemolytic anemia, is caused by deficiency of the erythrocyte membrane proteins. Five causative genes (ANK1, SPTB, SPTA1, SLC4A1, and EPB42) have been identified. To date, molecular genetic studies have been performed in different populations, including the American, European, Brazilian, Japanese and Korean populations, whereas only a few studies have been described in the Chinese population. Here, by reanalysis of the exome data, we revealed causative mutations and established a definitive diagnosis of HS in all 38 Chinese families. We found 34 novel mutations and four reported mutations in three known HS-causing genes-17 in ANK1, 17 in SPTB and four in SLC4A1, suggesting that ANK1 and SPTB are the major genes in Chinese patients with HS. All of the ANK1 or SPTB mutations, scattered throughout the entire genes, are non-recurrent; and most of them are null mutations, which might cause HS via a haploinsufficiency mechanism. De novo mutations in ANK1 or SPTB often occur with an unexpected high frequency (87.5% and 64.2%, respectively). Our study updates our knowledge about the genetic profile of HS in Chinese and shows that family-based, especially parent-offspring trio, sequencing analysis can help to increase the diagnostic power and improve diagnostic efficiency.
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5
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He Y, Jia S, Dewan RK, Liao N. Novel mutations in patients with hereditary red blood cell membrane disorders using next-generation sequencing. Gene 2017; 627:556-562. [PMID: 28694211 DOI: 10.1016/j.gene.2017.07.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Accepted: 07/06/2017] [Indexed: 02/07/2023]
Abstract
To diagnose and investigate the genotype-phenotype relationship in intractable hereditary red blood cell (RBC) membrane cases, we have utilized next-generation sequencing (NGS) to develop a high-throughput, highly sensitive assay. Three unrelated families including 15 individuals were analysed with a panel interrogating 600 genes related to haematopathy disorders. Where possible, inheritance patterns of pathogenic mutations were determined by sequencing the relatives. We identified 2 novel mutations in ANK1 (Y216X and E142X) responsible for hereditary spherocytosis (HS) that were stop-gain single nucleotide variants (SNVs). Furthermore, a novel SPTA1 mutation (H54P) was identified; it is a nonsynonymous SNV and is associated with hereditary elliptocytosis (HE). In addition, patients who also carried erythropoiesis gene mutations showed more severe disease phenotype. The NGS panel provides a fast and accurate method for molecular diagnosis in patients with intractable hereditary RBC membrane disorders. An approach integrating medical history, clinical and molecular testing, and pedigree analysis is beneficial for these patients and families.
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Affiliation(s)
- Yunyan He
- Department of Pediatrics, The First Affiliated Hospital of Guangxi Medical University, N0.6, Shuangyong Road, Qingxiu District, Nanning, Guangxi Province 530021, PR China
| | - Siyuan Jia
- Guangxi Medical University, N0.22, Shuangyong Road, Qingxiu District, Nanning, Guangxi Province 530021, PR China
| | - Roma Kajal Dewan
- Guangxi Medical University, N0.22, Shuangyong Road, Qingxiu District, Nanning, Guangxi Province 530021, PR China
| | - Ning Liao
- Department of Pediatrics, The First Affiliated Hospital of Guangxi Medical University, N0.6, Shuangyong Road, Qingxiu District, Nanning, Guangxi Province 530021, PR China.
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6
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Khanna MR, Mattie FJ, Browder KC, Radyk MD, Crilly SE, Bakerink KJ, Harper SL, Speicher DW, Thomas GH. Spectrin tetramer formation is not required for viable development in Drosophila. J Biol Chem 2014; 290:706-15. [PMID: 25381248 DOI: 10.1074/jbc.m114.615427] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The dominant paradigm for spectrin function is that (αβ)2-spectrin tetramers or higher order oligomers form membrane-associated two-dimensional networks in association with F-actin to reinforce the plasma membrane. Tetramerization is an essential event in such structures. We characterize the tetramerization interaction between α-spectrin and β-spectrins in Drosophila. Wild-type α-spectrin binds to both β- and βH-chains with high affinity, resembling other non-erythroid spectrins. However, α-spec(R22S), a tetramerization site mutant homologous to the pathological α-spec(R28S) allele in humans, eliminates detectable binding to β-spectrin and reduces binding to βH-spectrin ∼1000-fold. Even though spectrins are essential proteins, α-spectrin(R22S) rescues α-spectrin mutants to adulthood with only minor phenotypes indicating that tetramerization, and thus conventional network formation, is not the essential function of non-erythroid spectrin. Our data provide the first rigorous test for the general requirement for tetramer-based non-erythroid spectrin networks throughout an organism and find that they have very limited roles, in direct contrast to the current paradigm.
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Affiliation(s)
- Mansi R Khanna
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Floyd J Mattie
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Kristen C Browder
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Megan D Radyk
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Stephanie E Crilly
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Katelyn J Bakerink
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Sandra L Harper
- the Systems Biology Division, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - David W Speicher
- the Systems Biology Division, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - Graham H Thomas
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
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7
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The common hereditary elliptocytosis-associated α-spectrin L260P mutation perturbs erythrocyte membranes by stabilizing spectrin in the closed dimer conformation. Blood 2013; 122:3045-53. [PMID: 23974198 DOI: 10.1182/blood-2013-02-487702] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hereditary elliptocytosis (HE) and hereditary pyropoikilocytosis (HPP) are common disorders of erythrocyte shape primarily because of mutations in spectrin. The most common HE/HPP mutations are located distant from the critical αβ-spectrin tetramerization site, yet still interfere with formation of spectrin tetramers and destabilize the membrane by unknown mechanisms. To address this question, we studied the common HE-associated mutation, αL260P, in the context of a fully functional mini-spectrin. The mutation exhibited wild-type tetramer binding in univalent binding assays, but reduced binding affinity in bivalent-binding assays. Biophysical analyses demonstrated the mutation-containing domain was only modestly structurally destabilized and helical content was not significantly changed. Gel filtration analysis of the αL260P mini-spectrin indicated more compact structures for dimers and tetramers compared with wild-type. Chemical crosslinking showed structural changes in the mutant mini-spectrin dimer were primarily restricted to the vicinity of the αL260P mutation and indicated large conformational rearrangements of this region. These data indicate the mutation increased the stability of the closed dimer state, thereby reducing tetramer assembly and resulting in membrane destabilization. These results reveal a novel mechanism of erythrocyte membrane destabilization that could contribute to development of therapeutic interventions for mutations in membrane proteins containing spectrin-type domains associated with inherited disease.
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8
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Iolascon A, King MJ, Robertson S, Avvisati RA, Vitiello F, Asci R, Scoppettuolo MN, Delaunay J. A genomic deletion causes truncation of α-spectrin and ellipto-poikilocytosis. Blood Cells Mol Dis 2011; 46:195-200. [PMID: 21212007 DOI: 10.1016/j.bcmd.2010.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 12/02/2010] [Indexed: 11/18/2022]
Abstract
We report on a truncated α-spectrin chain, spectrin(Exeter), associated with ellipto-poikilocytosis. Analysis of erythrocyte membranes of affected individuals revealed a truncated α-spectrin chain with normal amounts of spectrin dimer. In the proband and her father, one haploid set of α-spectrin cDNA lacked exons 11 and 12, leading to partial deletion of repeats α4 and α5 (83 amino acids) of the α-spectrin chain. In one allele of genomic DNA, a 3567bp deletion starting in intron 10 and ending in intron 12 of the SPTA1 gene was found. The common polymorphic SPTA1 α(LELY) allele was found in trans to the SPTA1αExeter allele in the proband. The proband had inherited the SPTA1Exeter allele from her father and the αLELY allele from her healthy, asymptomatic mother. This is the first report of an interstitial deletion in the SPTA1 gene associated with ellipto-poikilocytosis.
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Affiliation(s)
- A Iolascon
- CEINGE Biotecnologie Avanzate, Napoli, Italy.
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9
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Long F, McElheny D, Jiang S, Park S, Caffrey MS, Fung LWM. Conformational change of erythroid alpha-spectrin at the tetramerization site upon binding beta-spectrin. Protein Sci 2007; 16:2519-30. [PMID: 17905835 PMCID: PMC2211704 DOI: 10.1110/ps.073115307] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
We previously determined the solution structures of the first 156 residues of human erythroid alpha-spectrin (SpalphaI-1-156, or simply Spalpha). Spalpha consists of the tetramerization site of alpha-spectrin and associates with a model beta-spectrin protein (Spbeta) with an affinity similar to that of native alpha- and beta-spectrin. Upon alphabeta-complex formation, our previous results indicate that there is an increase in helicity in the complex, suggesting conformational change in either Spalpha or Spbeta or in both. We have now used isothermal titration calorimetry, circular dichroism, static and dynamic light scattering, and solution NMR methods to investigate properties of the complex as well as the conformation of Spalpha in the complex. The results reveal a highly asymmetric complex, with a Perrin shape parameter of 1.23, which could correspond to a prolate ellipsoid with a major axis of about five and a minor axis of about one. We identified 12 residues, five prior to and seven following the partial domain helix in Spalpha that moved freely relative to the structural domain in the absence of Spbeta but when in the complex moved with a mobility similar to that of the structural domain. Thus, it appears that the association with Spbeta induced an unstructured-to-helical conformational transition in these residues to produce a rigid and asymmetric complex. Our findings may provide insight toward understanding different association affinities of alphabeta-spectrin at the tetramerization site for erythroid and non-erythroid spectrin and a possible mechanism to understand some of the clinical mutations, such as L49F of alpha-spectrin, which occur outside the functional partial domain region.
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Affiliation(s)
- Fei Long
- Department of Chemistry, University of Illinois at Chicago 60607, USA
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10
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Liem RI, Gallagher PG. Molecular mechanisms in the inherited red cell membrane disorders. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.ddmec.2005.11.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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11
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Sumandea CA, Fung LWM. Mutational effects at the tetramerization site of nonerythroid alpha spectrin. ACTA ACUST UNITED AC 2005; 136:81-90. [PMID: 15893590 DOI: 10.1016/j.molbrainres.2005.01.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Revised: 11/18/2004] [Accepted: 01/08/2005] [Indexed: 10/25/2022]
Abstract
Spectrin, a prominent cytoskeletal protein, exerts its fundamental role in cellular function by forming a sub-membrane filamentous network. An essential aspect of spectrin network formation is the tetramerization of spectrin alphabeta heterodimers. We used laboratory methods, the yeast two-hybrid system and random mutagenesis, to investigate, for the first time, effects of amino acid mutations on tetramerization of nonerythroid (brain) spectrin (fodrin). Based on high sequence homology with erythroid spectrin, we assume the putative tetramerization region of nonerythroid alpha-spectrin at the N-terminal region. We introduced mutations in the region consisting of residues 1-45 and studied mutational effects on spectrin alphabeta association to form tetramers. We detected single, double, and triple mutations involving 24 residues in this region. These amino acid mutations of nonerythroid alpha-spectrin exhibit full, partial, or no effect on the association with nonerythroid beta-spectrin. Single amino acid mutations in the region of residues 1-9 (D2Y, G5V, V6D, and V8M) did not affect the association. However, seven single mutations (I15F, I15N, R18G, V22D, R25P, Y26N, and R28P) affected the alphabeta association. These mutations were clustered in the region predicted by sequence alignment to be crucial in nonerythroid alpha-spectrin for tetramerization, a region that spanned residues 12-36, corresponding to the partial domain Helix C' (residues 21-45) in erythroid alpha-spectrin. In addition, two other mutations, one upstream and one downstream of this region at positions 10 (E10D) and 37 (R37P), also affected the alphabeta association. Our results implied nonerythroid alpha-spectrin partial domain helix may be longer than Helix C' (residues 21-45 and a total of 25 residues) in erythroid alpha-spectrin and spanned at least residues 10-37. It is interesting to note that seven out of these nine single mutations (I15F, I15N, R18G, V22D, R25P, Y26N, R37P) were at the a, d, e or g heptad positions based on sequence alignment with erythroid alpha-spectrin. Four of the mutated residues (I15, R18, V22, R25) are conserved in both erythroid and nonerythroid spectrin. These positions were previously identified as hot spots in erythroid alpha-spectrin that lead to severe hematological symptoms. This study clearly demonstrated that single mutation in a region predicted to be critical functionally in nonerythroid alpha-spectrin indeed leads to functional abnormalities and may lead to neurological disorders.
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Affiliation(s)
- Claudia A Sumandea
- Loyola University of Chicago, Department of Chemistry, 6525 N Sheridan Road, Chicago, IL 60626, USA
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12
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Vittitow J, Borrás T. Genes expressed in the human trabecular meshwork during pressure-induced homeostatic response. J Cell Physiol 2004; 201:126-37. [PMID: 15281095 DOI: 10.1002/jcp.20030] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Physiological pressure inside the eye is maintained by a resistance mechanism provided by the trabecular meshwork tissue. In most cases, prolonged, elevated pressure leads to an eye pathology characterized by retinal ganglion cell (RGC) degeneration, optic nerve damage, and non-remedial blindness. We are investigating the regulation of trabecular meshwork genes in response to elevated pressure. Using perfused organ cultures from postmortem human donors, we have previously demonstrated the presence of a homeostatic mechanism at 2-4 days of pressure insult (Borrás et al. 2002, Invest Ophthalmol Vis Sci 43:33-40). Here, we sought to identify trabecular meshwork genes whose expression was altered during this homeostatic period. By macroarray hybridization, we compared the expression profiles of high-pressure (HP) and normal-pressure (NP) treated eyes from the same individual (n = 3 pairs). Our results identified 40 upregulated and 14 downregulated genes. The highest proportion of upregulated genes encoded proteins involved in signal transduction (32%). Among the potentially relevant genes, PIP 5K1C, VIP, tropomodulin, and MMP2 encoded mediators known to influence outflow resistance. Others encoded functions which are new for the trabecular meshwork, but which are intrinsic to unrelated tissues. These new mechanisms appear as they could be of benefit for trabecular meshwork function. Matrix Gla protein (MGP), perlecan, osteomodulin, and osteoblast-specific factor are essential in cartilage and bone physiology whereas spectrin and ICAM4 are specific for blood cells and crucial in maintaining their shape and adhesion. In addition, MGP transcripts were stimulated by extracellular calcium and downregulated by TGF-beta1. We propose that MGP might be an important player in the adaptive homeostatic mechanism by contributing to maintain a softer trabecular meshwork tissue and facilitate aqueous humor outflow.
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Affiliation(s)
- Jason Vittitow
- Department of Ophthalmology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
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13
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Gallagher PG, Zhang Z, Morrow JS, Forget BG. Mutation of a highly conserved isoleucine disrupts hydrophobic interactions in the alpha beta spectrin self-association binding site. J Transl Med 2004; 84:229-34. [PMID: 14661034 DOI: 10.1038/labinvest.3700029] [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] [Indexed: 11/09/2022] Open
Abstract
We studied an infant with severe neonatal hemolytic anemia and hyperbilirubinemia that evolved into a partially compensated ellipto-poikilocytic anemia. His father had typical elliptocytosis. Their erythrocyte membranes demonstrated structural and functional defects in spectrin. Genetic studies revealed that the proband and his father were heterozygous for an alpha-spectrin mutation, Ile24Thr, in the alpha beta spectrin self-association binding site. The proband also carried the low expression allele alpha(LELY) in trans, influencing the clinical phenotype. The importance of isoleucine in this position of the proposed triple helical model of spectrin repeats is highlighted by its evolutionary conservation in all alpha spectrins from Drosophila to humans. Molecular modeling demonstrated that replacement of a hydrophobic isoleucine with a hydrophilic threonine disrupts highly conserved hydrophobic interactions in the interior of the spectrin triple helix critical for spectrin function.
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Affiliation(s)
- Patrick G Gallagher
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06520-8064, USA.
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14
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Park S, Johnson ME, Fung LWM. Nuclear magnetic resonance studies of mutations at the tetramerization region of human alpha spectrin. Blood 2002; 100:283-8. [PMID: 12070038 DOI: 10.1182/blood.v100.1.283] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many spectrin mutations that destabilize tetramer formation and lead to hereditary hemolytic anemias are located at the N-terminal region of alpha-spectrin, with the Arg28 position considered to be a mutation hot spot. We have introduced mutations at positions 28 and 45 into a model peptide, Sp alpha 1-156, consisting of the first 156 residues in the N-terminal region of alpha-spectrin (alpha N). The association of these alpha-spectrin peptides that have single amino acid replacements with a beta-spectrin model peptide, consisting of the C-terminal region of beta-spectrin (beta C), was determined, and structural changes due to amino acid replacements were monitored by nuclear magnetic resonance (NMR). We found evidence for similar and very localized structural changes in Sp alpha 1-156Arg45Thr and Sp alpha 1-156Arg45Ser, although these 2 mutant peptides associated with beta-spectrin peptide with significantly differing affinities. The Sp alpha 1-156Arg28Ser peptide showed an affinity for the beta-spectrin peptide comparable to that of Sp alpha 1-156Arg45Ser, but it exhibited substantial and widespread spectral changes. Our results suggest that both Arg45 replacements induce only minor structural perturbations in the first helix of Sp alpha 1-156, but the Arg28Ser replacement affects both the first helix and the following structural domain. Our results also indicate that the mechanism for reduced spectrin tetramerization is through mutation-induced changes in molecular recognition at the alpha beta-tetramerization site, rather than through conformational disruption, as has been suggested in prior literature.
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Affiliation(s)
- Sunghyouk Park
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 60607, USA
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15
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Luo BH, Mehboob S, Hurtuk MG, Pipalia NH, Fung LWM. Important region in the beta-spectrin C-terminus for spectrin tetramer formation. Eur J Haematol 2002; 68:73-9. [PMID: 12038451 DOI: 10.1034/j.1600-0609.2002.01569.x] [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: 11/23/2022]
Abstract
Many hereditary hemolytic anemias are due to spectrin mutations at the C-terminal region of beta-spectrin (the betaC region) that destabilize spectrin tetramer formation. However, little is known about the betaC region of spectrin. We have prepared four recombinant beta-peptides of different lengths from human erythrocyte spectrin, all starting at position 1898 of the C-terminal region, but terminating at position 2070, 2071, 2072 or 2073. Native polyacrylamide gel electrophoresis showed that the two peptides terminating at positions 2070 and 2071 did not associate with an N-terminal region alpha-peptide (Spalpha1-156) in the micromolar range. However, the peptides that terminated at positions 2072 and 2073 associated with the alpha-peptide. Circular dichroism results showed that the unassociated helices in both alpha- and beta-peptides became associated, presumably to form a helical bundle, for those beta-peptides that formed an alphabeta complex, but not for those beta-peptides that did not form an alphabeta complex. In addition, upon association, an increase in the alpha-helical content was observed. These results showed that the beta-peptides ending prior to residue 2072 (Thr) would not associate with alpha-peptide, and that no helical bundling of the partial domains was observed. Thus, we suggest that the C-terminal segment of beta-spectrin, starting from residue 2073 (Thr), is not critical to spectrin tetramer formation. However, the C-terminal region ending with residue 2072 is important for its association with alpha-spectrin in forming tetramers.
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Affiliation(s)
- Bing-Hao Luo
- Department of Chemistry, Loyola University of Chicago, IL 60626, USA
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16
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Zhang Z, Weed SA, Gallagher PG, Morrow JS. Dynamic molecular modeling of pathogenic mutations in the spectrin self-association domain. Blood 2001; 98:1645-53. [PMID: 11535493 DOI: 10.1182/blood.v98.6.1645] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Disruption of spectrin self-association underlies many inherited hemolytic disorders. Using dynamic modeling and energy minimization, the 3-dimensional structure of the self-association domain has been estimated in human erythrocyte spectrin and the structural consequences of 17 elliptogenic mutations determined. The predicted structure of the normal self-association domain was remarkably similar to the crystal structure of the Drosophila alpha-spectrin 14th repeat unit, despite replacement in the human sequence of over 70% of the amino acids relative to fly spectrin, including 2 prolines in the human sequence that appear in helical regions of the fly structure. The predicted structure placed all hydrophilic residues at the surface and identified 4 salt bridges, 9 hydrophobic interactions, and 4 H-bonds that stabilize the native self-association unit. Remarkably, every pathologic point mutation, including seemingly conservative substitutions such as G for A, A for V, or K for R (single-letter amino acid codes), led to conformational rearrangements in the predicted structure. The degree of structural disruption, as measured by root-mean-square deviation of the predicted backbone structure from the Drosophila structure, correlated strongly with the severity of clinical disease associated with each mutation. This approach thus enables an accurate prediction, from the primary sequence, of the clinical consequences of specific point mutations in spectrin. The 3-dimensional structure of the self-association domain derived here is likely to be accurate. It provides a powerful heuristic model for understanding how point mutations disrupt cytoskeletal function in a variety of hemolytic disorders.
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MESH Headings
- Amino Acid Sequence
- Anemia, Hemolytic, Congenital/diagnosis
- Anemia, Hemolytic, Congenital/genetics
- Animals
- Drosophila/genetics
- Elliptocytosis, Hereditary/diagnosis
- Elliptocytosis, Hereditary/genetics
- Humans
- Models, Molecular
- Molecular Sequence Data
- Point Mutation
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Sequence Homology, Amino Acid
- Spectrin/chemistry
- Spectrin/genetics
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Affiliation(s)
- Z Zhang
- Department of Pathology, Yale University, New Haven, CT, USA
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17
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Winkelmann J. Hemolytic Anemia Associated with Red Cell Membrane Defects. Diagn Pathol 2000. [DOI: 10.1201/b13994-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Affiliation(s)
- M F McMullin
- Department of Haematology, University of Belfast, UK.
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Abstract
Defects of alpha spectrin have been identified in many cases of hereditary elliptocytosis (HE) and hereditary pyropoikilocytosis (HPP). To aid in the genetic analysis of families with these disorders, the locations of three alpha-spectrin gene polymorphisms were mapped, the genetic basis of these polymorphisms identified, and PCR-based assays designed for their identification. The frequencies of these polymorphisms were determined in two populations and in patients with alphaI/50a HE and HPP. These studies identified two distinct haplotypes and provided evidence that two HE/HPP mutations associated with the alphaI/50a protein phenotype, L207P and L260P, arose on separate chromosomal backgrounds.
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Affiliation(s)
- P G Gallagher
- Department of Pediatrics, Internal Medicine and Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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