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Ehm PAH, Horn S, Hoffer K, Kriegs M, Horn M, Giehler S, Nalaskowski M, Rehbach C, Horstmann MA, Jücker M. Ikaros sets the threshold for negative B-cell selection by regulation of the signaling strength of the AKT pathway. Cell Commun Signal 2024; 22:360. [PMID: 38992657 PMCID: PMC11241878 DOI: 10.1186/s12964-024-01732-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 07/02/2024] [Indexed: 07/13/2024] Open
Abstract
Inhibitory phosphatases, such as the inositol-5-phosphatase SHIP1 could potentially contribute to B-cell acute lymphoblastic leukemia (B-ALL) by raising the threshold for activation of the autoimmunity checkpoint, allowing malignant cells with strong oncogenic B-cell receptor signaling to escape negative selection. Here, we show that SHIP1 is differentially expressed across B-ALL subtypes and that high versus low SHIP1 expression is associated with specific B-ALL subgroups. In particular, we found high SHIP1 expression in both, Philadelphia chromosome (Ph)-positive and ETV6-RUNX1-rearranged B-ALL cells. As demonstrated by targeted knockdown of SHIP1 by RNA interference, proliferation of B-ALL cells in vitro and their tumorigenic spread in vivo depended in part on SHIP1 expression. We investigated the regulation of SHIP1, as an important antagonist of the AKT signaling pathway, by the B-cell-specific transcription factor Ikaros. Targeted restoration of Ikaros and pharmacological inhibition of the antagonistic casein kinase 2, led to a strong reduction in SHIP1 expression and at the same time to a significant inhibition of AKT activation and cell growth. Importantly, the tumor suppressive function of Ikaros was enhanced by a SHIP1-dependent additive effect. Furthermore, our study shows that all three AKT isoforms contribute to the pro-mitogenic and anti-apoptotic signaling in B-ALL cells. Conversely, hyperactivation of a single AKT isoform is sufficient to induce negative selection by increased oxidative stress. In summary, our study demonstrates the regulatory function of Ikaros on SHIP1 expression in B-ALL and highlights the relevance of sustained SHIP1 expression to prevent cells with hyperactivated PI3K/AKT/mTOR signaling from undergoing negative selection.
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Affiliation(s)
- Patrick A H Ehm
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, Hamburg, 20246, Germany.
- Department of Pediatric Oncology and Hematology, Research Institute Children's Cancer Center Hamburg, University Medical Center, Hamburg, 20246, Germany.
| | - Stefan Horn
- Research Department Cell and Gene Therapy, Department of Stem Cell Transplantation, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Konstantin Hoffer
- UCCH Kinomics Core Facility, University Cancer Center Hamburg (UCCH), University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
- Department of Radiotherapy and Radiation Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Malte Kriegs
- UCCH Kinomics Core Facility, University Cancer Center Hamburg (UCCH), University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
- Department of Radiotherapy and Radiation Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Michael Horn
- University Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
- Mildred Scheel Cancer Career Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, 20246, Germany
| | - Susanne Giehler
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, Hamburg, 20246, Germany
| | - Marcus Nalaskowski
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, Hamburg, 20246, Germany
| | - Christoph Rehbach
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, Hamburg, 20246, Germany
- Department of Human Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Martin A Horstmann
- Department of Pediatric Oncology and Hematology, Research Institute Children's Cancer Center Hamburg, University Medical Center, Hamburg, 20246, Germany
| | - Manfred Jücker
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, Hamburg, 20246, Germany
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Ehm P, Bettin B, Jücker M. Activated Src kinases downstream of BCR-ABL and Flt3 induces proteasomal degradation of SHIP1 by phosphorylation of tyrosine 1021. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119467. [PMID: 36958526 DOI: 10.1016/j.bbamcr.2023.119467] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 03/03/2023] [Accepted: 03/12/2023] [Indexed: 03/25/2023]
Abstract
Within the various subtypes of ALL, patients with a BCR-ABL-positive background as well as with a genetic change in the KMT2A gene have by far the worst survival probabilities. Interestingly, both subtypes are characterized by highly activated tyrosine kinases. SHIP1 serves as an important negative regulator of the PI3K/AKT signaling pathway, which is often constitutively activated in ALL. The protein expression of SHIP1 is decreased in most T-ALL and in some subgroups of B-ALL. In this study, we analyzed the expression of SHIP1 protein in detail in the context of groups with aberrant activated tyrosine kinases, namely BCR-ABL (Ph+) and Flt3 (KMT2A translocations). We demonstrate that constitutively activated Src kinases downstream of BCR-ABL and receptor tyrosine kinases reduce the SHIP1 expression in a SHIP1-Y1021 phosphorylated-dependent manner with subsequent ubiquitin marked proteasomal degradation. Inhibition of BCR-ABL (Imatinib), Flt3 (Quizartinib) or Src-Kinase-Family (Saracatinib) leads to significant reconstitution of SHIP1 protein expression. These results further support a functional role of SHIP1 as tumor suppressor protein and could be the basis for the establishment of a targeted therapy form.
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Affiliation(s)
- Patrick Ehm
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany; Research Institute Children's Cancer Center Hamburg, Hamburg and Dept. of Pediatric Oncology and Hematology, University Medical Center, Hamburg, Germany.
| | - Bettina Bettin
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Manfred Jücker
- Institute of Biochemistry and Signal Transduction, Center for Experimental Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
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3
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Soares BP, Santos JH, Martins M, Almeida MR, Santos NV, Freire MG, Santos-Ebinuma VC, Coutinho JA, Pereira JF, Ventura SP. Purification of green fluorescent protein using fast centrifugal partition chromatography. Sep Purif Technol 2021. [DOI: 10.1016/j.seppur.2020.117648] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Cao X, Sun Y, Lu P, Zhao M. Fluorescence imaging of intracellular nucleases-A review. Anal Chim Acta 2020; 1137:225-237. [PMID: 33153605 DOI: 10.1016/j.aca.2020.08.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 08/04/2020] [Accepted: 08/06/2020] [Indexed: 11/28/2022]
Abstract
Nucleases play crucial roles in maintaining genomic integrity. Visualization of intracellular distribution and translocation of nucleases are of great importance for understanding the in-vivo physiological functions of these enzymes and their roles in DNA repair and other cellular signaling pathways. Here we review the recently developed approaches for fluorescence imaging of nucleases in various eukaryotic cells. We mainly focused on the immunofluorescence techniques, the genetically encoded fluorescent probes and the chemically synthesized fluorescent DNA-substrate probes that enabled in-situ visualization of the subcellular localization of nucleases and their interactions with other protein/DNA molecules within cells. The targeted nucleases included important endonucleases, 3' exonucleases and 5' exonucleases that were involved in the DNA damage repair pathways and the intracellular DNA degradation. The advantages and limitations of the available tools were summarized and discussed.
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Affiliation(s)
- Xiangjian Cao
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Ying Sun
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Peng Lu
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Meiping Zhao
- Beijing National Laboratory for Molecular Sciences, MOE Key Laboratory of Bioorganic Chemistry and Molecular Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
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5
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Woloschuk RM, Reed PMM, McDonald S, Uppalapati M, Woolley GA. Yeast Two-Hybrid Screening of Photoswitchable Protein-Protein Interaction Libraries. J Mol Biol 2020; 432:3113-3126. [PMID: 32198111 DOI: 10.1016/j.jmb.2020.03.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/04/2020] [Accepted: 03/09/2020] [Indexed: 02/08/2023]
Abstract
Although widely used in the detection and characterization of protein-protein interactions, Y2H screening has been under-used for the engineering of new optogenetic tools or the improvement of existing tools. Here we explore the feasibility of using Y2H selection and screening to evaluate libraries of photoswitchable protein-protein interactions. We targeted the interaction between circularly permuted photoactive yellow protein (cPYP) and its binding partner binder of PYP dark-state (BoPD) by mutating a set of four surface residues of cPYP that contribute to the binding interface. A library of ~10,000 variants was expressed in yeast together with BoPD in a Y2H format. An initial selection for the cPYP/BoPD interaction was performed using a range of concentrations of the cPYP chromophore. As expected, the majority (>90% of cPYP variants) no longer bound to BoPD. Replica plating was then used to evaluate the photoswitchability of the surviving clones. Photoswitchable cPYP variants with BoPD affinities equal to, or higher than, native cPYP were recovered in addition to variants with altered photocycles and binders that interacted with BoPD as apo-proteins. Y2H results reflected protein-protein interaction affinity, expression, photoswitchability, and chromophore uptake, and correlated well with results obtained both in vitro and in mammalian cells. Thus, by systematic variation of selection parameters, Y2H screens can be effectively used to generate new optogenetic tools for controlling protein-protein interactions for use in diverse settings.
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Affiliation(s)
- Ryan M Woloschuk
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Canada, M5S 3H6
| | - P Maximilian M Reed
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Canada, M5S 3H6
| | - Sherin McDonald
- Department of Pathology and Laboratory Medicine, University of Saskatchewan, 107 Wiggins Rd, Saskatoon, SK, Canada, S7N 5E5
| | - Maruti Uppalapati
- Department of Pathology and Laboratory Medicine, University of Saskatchewan, 107 Wiggins Rd, Saskatoon, SK, Canada, S7N 5E5
| | - G Andrew Woolley
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Canada, M5S 3H6.
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Fonseca JP, Bonny AR, Kumar GR, Ng AH, Town J, Wu QC, Aslankoohi E, Chen SY, Dods G, Harrigan P, Osimiri LC, Kistler AL, El-Samad H. A Toolkit for Rapid Modular Construction of Biological Circuits in Mammalian Cells. ACS Synth Biol 2019; 8:2593-2606. [PMID: 31686495 DOI: 10.1021/acssynbio.9b00322] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The ability to rapidly assemble and prototype cellular circuits is vital for biological research and its applications in biotechnology and medicine. Current methods for the assembly of mammalian DNA circuits are laborious, slow, and expensive. Here we present the Mammalian ToolKit (MTK), a Golden Gate-based cloning toolkit for fast, reproducible, and versatile assembly of large DNA vectors and their implementation in mammalian models. The MTK consists of a curated library of characterized, modular parts that can be assembled into transcriptional units and further weaved into complex circuits. We showcase the capabilities of the MTK by using it to generate single-integration landing pads, create and deliver libraries of protein variants and sgRNAs, and iterate through dCas9-based prototype circuits. As a biological proof of concept, we demonstrate how the MTK can speed the generation of noninfectious viral circuits to enable rapid testing of pharmacological inhibitors of emerging viruses that pose a major threat to human health.
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Affiliation(s)
- João Pedro Fonseca
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
| | - Alain R. Bonny
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
| | - G. Renuka Kumar
- Chan Zuckerberg Biohub, San Francisco, California 94158, United States
| | - Andrew H. Ng
- Cell Design Initiative, University of California, San Francisco, San Francisco, California 94158, United States
| | - Jason Town
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
| | - Qiu Chang Wu
- Harvard Systems Biology Graduate Program, Cambridge, Massachusetts 02138, United States
| | - Elham Aslankoohi
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
| | - Susan Y. Chen
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
| | - Galen Dods
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
| | - Patrick Harrigan
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
| | - Lindsey C. Osimiri
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
- The UC Berkeley−UCSF Graduate Program in Bioengineering, University of California, San Francisco, San Francisco, California 94132, United States
| | - Amy L. Kistler
- Chan Zuckerberg Biohub, San Francisco, California 94158, United States
| | - Hana El-Samad
- Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, United States
- Chan Zuckerberg Biohub, San Francisco, California 94158, United States
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Ali R, Ramadurai S, Barry F, Nasheuer HP. Optimizing fluorescent protein expression for quantitative fluorescence microscopy and spectroscopy using herpes simplex thymidine kinase promoter sequences. FEBS Open Bio 2018; 8:1043-1060. [PMID: 29928582 PMCID: PMC5985997 DOI: 10.1002/2211-5463.12432] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 03/19/2018] [Accepted: 04/10/2018] [Indexed: 12/22/2022] Open
Abstract
The modulation of expression levels of fluorescent fusion proteins (FFPs) is central for recombinant DNA technologies in modern biology as overexpression of proteins contributes to artifacts in biological experiments. In addition, some microscopy techniques such as fluorescence correlation spectroscopy (FCS) and single-molecule-based techniques are very sensitive to high expression levels of FFPs. To reduce the levels of recombinant protein expression in comparison with the commonly used, very strong CMV promoter, the herpes simplex virus thymidine kinase (TK) gene promoter, and mutants thereof were analyzed. Deletion mutants of the TK promoter were constructed and introduced into the Gateway® system for ectopic expression of enhanced green fluorescent protein (eGFP), monomeric cherry (mCherry), and FFPs containing these FPs. Two promoter constructs, TK2ST and TKTSC, were established, which have optimal low expression levels suitable for FCS studies in U2OS, HeLa CCL2, NIH 3T3, and BALB/c cells. Interestingly, when tested in these four cell lines, promoter constructs having a deletion within TK gene 5'-UTR showed significantly higher protein expression levels than the equivalent constructs lacking this deletion. This suggests that a negative regulatory element is localized within the TK gene 5'-UTR.
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Affiliation(s)
- Rizwan Ali
- Systems Biology IrelandNUI GalwayIreland
- BiochemistrySchool of Natural Sciences and Centre for Chromosome BiologyNational University of Ireland GalwayIreland
- Present address:
Medical Core Facility & Research PlatformsKing Abdullah International Medical Research CenterNational Guard Health AffairsP.O. Box 3660Riyadh11481 Mail Code 1515Saudi Arabia
| | - Sivaramakrishnan Ramadurai
- Systems Biology IrelandNUI GalwayIreland
- BiochemistrySchool of Natural Sciences and Centre for Chromosome BiologyNational University of Ireland GalwayIreland
- Present address:
School of Chemical SciencesDublin City UniversityDublin‐9Ireland
| | - Frank Barry
- Systems Biology IrelandNUI GalwayIreland
- Regenerative Medicine InstituteNational University of Ireland GalwayIreland
| | - Heinz Peter Nasheuer
- Systems Biology IrelandNUI GalwayIreland
- BiochemistrySchool of Natural Sciences and Centre for Chromosome BiologyNational University of Ireland GalwayIreland
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A TB40/E-derived human cytomegalovirus genome with an intact US-gene region and a self-excisable BAC cassette for immunological research. Biotechniques 2017; 63:205-214. [DOI: 10.2144/000114606] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Accepted: 09/27/2017] [Indexed: 11/23/2022] Open
Abstract
For immunological research on the human cytomegalovirus (HCMV), a virus that combines the broad cell tropism of clinical isolates, efficient replication in cell culture, the complete set of MHC-I modulator genes, and suitability for genetic engineering is desired. Here, we aimed to generate a genetically complete derivative of HCMV strain TB40/E as a bacterial artificial chromosome (BAC) with a self-excisable BAC cassette. The BAC cassette was inserted into the US2–US6 gene region (yielding TB40-BACKL7), relocated into the UL73/UL74 region with modifications that favor excision of the BAC cassette during replication in fibroblasts, and finally the US2–US6 region was restored, resulting in BAC clone TB40-BACKL7-SE When this BAC clone was transfected into fibroblasts at efficiencies >0.1%, replicating virus that had lost the BAC cassette appeared within 2 weeks after transfection, grew to high titers, and displayed the broad tropism of the parental virus. The degree of MHC-I down-regulation by this virus was consistent with functional restoration of US2–US6. To enable detection of infected cells by flow cytometry, an enhanced green fluorescent protein (EGFP)-expression cassette was inserted downstream of US34A, yielding the fluorescent virus RV-TB40-BACKL7-SE-EGFP.
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EGFP oligomers as natural fluorescence and hydrodynamic standards. Sci Rep 2016; 6:33022. [PMID: 27622431 PMCID: PMC5020695 DOI: 10.1038/srep33022] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/10/2016] [Indexed: 01/29/2023] Open
Abstract
EGFP oligomers are convenient standards for experiments on fluorescent protein-tagged biomolecules. In this study, we characterized their hydrodynamic and fluorescence properties. Diffusion coefficients D of EGFP1-4 were determined by analytical ultracentrifugation with fluorescence detection and by fluorescence correlation spectroscopy (FCS), yielding 83.4…48.2 μm(2)/s and 97.3…54.8 μm(2)/s from monomer to tetramer. A "barrels standing in a row" model agreed best with the sedimentation data. Oligomerization red-shifted EGFP emission spectra without any shift in absorption. Fluorescence anisotropy decreased, indicating homoFRET between the subunits. Fluorescence lifetime decreased only slightly (4%) indicating insignificant quenching by FRET to subunits in non-emitting states. FCS-measured D, particle number and molecular brightness depended on dark states and light-induced processes in distinct subunits, resulting in a dependence on illumination power different for monomers and oligomers. Since subunits may be in "on" (bright) or "off" (dark) states, FCS-determined apparent brightness is not proportional to that of the monomer. From its dependence on the number of subunits, the probability of the "on" state for a subunit was determined to be 96% at pH 8 and 77% at pH 6.38, i.e., protonation increases the dark state. These fluorescence properties of EGFP oligomeric standards can assist interpreting results from oligomerized EGFP fusion proteins of biological interest.
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Debray FG, Stümpfig C, Vanlander AV, Dideberg V, Josse C, Caberg JH, Boemer F, Bours V, Stevens R, Seneca S, Smet J, Lill R, van Coster R. Mutation of the iron-sulfur cluster assembly gene IBA57 causes fatal infantile leukodystrophy. J Inherit Metab Dis 2015; 38:1147-53. [PMID: 25971455 DOI: 10.1007/s10545-015-9857-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Revised: 04/20/2015] [Accepted: 04/22/2015] [Indexed: 11/29/2022]
Abstract
Leukodystrophies are a heterogeneous group of severe genetic neurodegenerative disorders. A multiple mitochondrial dysfunctions syndrome was found in an infant presenting with a progressive leukoencephalopathy. Homozygosity mapping, whole exome sequencing, and functional studies were used to define the underlying molecular defect. Respiratory chain studies in skeletal muscle isolated from the proband revealed a combined deficiency of complexes I and II. In addition, western blotting indicated lack of protein lipoylation. The combination of these findings was suggestive for a defect in the iron-sulfur (Fe/S) protein assembly pathway. SNP array identified loss of heterozygosity in large chromosomal regions, covering the NFU1 and BOLA3, and the IBA57 and ABCB10 candidate genes, in 2p15-p11.2 and 1q31.1-q42.13, respectively. A homozygous c.436C > T (p.Arg146Trp) variant was detected in IBA57 using whole exome sequencing. Complementation studies in a HeLa cell line depleted for IBA57 showed that the mutant protein with the semi-conservative amino acid exchange was unable to restore the biochemical phenotype indicating a loss-of-function mutation of IBA57. In conclusion, defects in the Fe/S protein assembly gene IBA57 can cause autosomal recessive neurodegeneration associated with progressive leukodystrophy and fatal outcome at young age. In the affected patient, the biochemical phenotype was characterized by a defect in the respiratory chain complexes I and II and a decrease in mitochondrial protein lipoylation, both resulting from impaired assembly of Fe/S clusters.
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Affiliation(s)
| | - Claudia Stümpfig
- Institut für Zytobiologie und Zytopathologie, Philipps-Universität, Marburg, Germany
| | - Arnaud V Vanlander
- Division of Pediatric Neurology and Metabolism, Department of Pediatrics, Gent University Hospital, Gent, Belgium
| | - Vinciane Dideberg
- Metabolic Unit, Department of Medical Genetics, Sart-Tilman University Hospital, Liège, Belgium
| | - Claire Josse
- GIGA Research, Human Genetics Unit, University of Liège, Liège, Belgium
| | - Jean-Hubert Caberg
- Metabolic Unit, Department of Medical Genetics, Sart-Tilman University Hospital, Liège, Belgium
| | - François Boemer
- Metabolic Unit, Department of Medical Genetics, Sart-Tilman University Hospital, Liège, Belgium
| | - Vincent Bours
- Metabolic Unit, Department of Medical Genetics, Sart-Tilman University Hospital, Liège, Belgium
| | - René Stevens
- Department of Pediatrics, Clinique de l'Espérance, Liège, Belgium
| | - Sara Seneca
- Center of Medical Genetics, UZ Brussel and Reproduction and Genetics, Vrije Universiteit Brussel, Brussels, Belgium
| | - Joél Smet
- Division of Pediatric Neurology and Metabolism, Department of Pediatrics, Gent University Hospital, Gent, Belgium
| | - Roland Lill
- Institut für Zytobiologie und Zytopathologie, Philipps-Universität, Marburg, Germany.
- LOEWE Zentrum für Synthetische Mikrobiologie SynMikro, Philipps-Universität, Marburg, Germany.
| | - Rudy van Coster
- Division of Pediatric Neurology and Metabolism, Department of Pediatrics, Gent University Hospital, Gent, Belgium.
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