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Miersch S, Li Z, Saberianfar R, Ustav M, Brett Case J, Blazer L, Chen C, Ye W, Pavlenco A, Gorelik M, Garcia Perez J, Subramania S, Singh S, Ploder L, Ganaie S, Chen RE, Leung DW, Pandolfi PP, Novelli G, Matusali G, Colavita F, Capobianchi MR, Jain S, Gupta JB, Amarasinghe GK, Diamond MS, Rini J, Sidhu SS. Tetravalent SARS-CoV-2 Neutralizing Antibodies Show Enhanced Potency and Resistance to Escape Mutations. J Mol Biol 2021; 433:167177. [PMID: 34329642 PMCID: PMC8316672 DOI: 10.1016/j.jmb.2021.167177] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/17/2021] [Accepted: 07/21/2021] [Indexed: 12/16/2022]
Abstract
Neutralizing antibodies (nAbs) hold promise as therapeutics against COVID-19. Here, we describe protein engineering and modular design principles that have led to the development of synthetic bivalent and tetravalent nAbs against SARS-CoV-2. The best nAb targets the host receptor binding site of the viral S-protein and tetravalent versions block entry with a potency exceeding bivalent nAbs by an order of magnitude. Structural studies show that both the bivalent and tetravalent nAbs can make multivalent interactions with a single S-protein trimer, consistent with the avidity and potency of these molecules. Significantly, we show that the tetravalent nAbs show increased tolerance to potential virus escape mutants and an emerging variant of concern. Bivalent and tetravalent nAbs can be produced at large-scale and are as stable and specific as approved antibody drugs. Our results provide a general framework for enhancing antiviral therapies against COVID-19 and related viral threats, and our strategy can be applied to virtually any antibody drug.
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Affiliation(s)
- Shane Miersch
- The Donnelly Centre, University of Toronto, Toronto, Canada
| | - Zhijie Li
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | | | | | - James Brett Case
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Levi Blazer
- The Donnelly Centre, University of Toronto, Toronto, Canada
| | - Chao Chen
- The Donnelly Centre, University of Toronto, Toronto, Canada
| | - Wei Ye
- The Donnelly Centre, University of Toronto, Toronto, Canada
| | | | - Maryna Gorelik
- The Donnelly Centre, University of Toronto, Toronto, Canada
| | | | | | - Serena Singh
- The Donnelly Centre, University of Toronto, Toronto, Canada
| | - Lynda Ploder
- The Donnelly Centre, University of Toronto, Toronto, Canada
| | - Safder Ganaie
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Rita E Chen
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Daisy W Leung
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Pier Paolo Pandolfi
- Renown Institute for Cancer, Nevada System of Higher Education, Reno, NV, USA; Department of Molecular Biotechnologies & Health Sciences, Molecular Biotechnology Center, University of Turin, Italy
| | - Giuseppe Novelli
- Department of Biomedicine and Prevention, Tor Vergata University of Rome, 00133 Rome, Italy
| | - Giulia Matusali
- Laboratory of Virology, National Institute for Infectious Diseases "L. Spallanzani" IRCCS, Rome, Italy
| | - Francesca Colavita
- Laboratory of Virology, National Institute for Infectious Diseases "L. Spallanzani" IRCCS, Rome, Italy
| | - Maria R Capobianchi
- Laboratory of Virology, National Institute for Infectious Diseases "L. Spallanzani" IRCCS, Rome, Italy
| | | | - J B Gupta
- Virna Therapeutics, West Roxbury, MA, USA
| | - Gaya K Amarasinghe
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Michael S Diamond
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA; Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, USA; Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - James Rini
- Department of Molecular Genetics, University of Toronto, Toronto, Canada; Department of Biochemistry, University of Toronto, Toronto, Canada.
| | - Sachdev S Sidhu
- The Donnelly Centre, University of Toronto, Toronto, Canada.
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2
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Miersch S, Li Z, Saberianfar R, Ustav M, Case JB, Blazer L, Chen C, Ye W, Pavlenco A, Gorelik M, Perez JG, Subramania S, Singh S, Ploder L, Ganaie S, Chen RE, Leung DW, Pandolfi PP, Novelli G, Matusali G, Colavita F, Capobianchi MR, Jain S, Gupta JB, Amarasinghe GK, Diamond MS, Rini J, Sidhu SS. Tetravalent SARS-CoV-2 Neutralizing Antibodies Show Enhanced Potency and Resistance to Escape Mutations. bioRxiv 2020. [PMID: 33398270 DOI: 10.1101/2020.10.31.362848] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Neutralizing antibodies (nAbs) hold promise as effective therapeutics against COVID-19. Here, we describe protein engineering and modular design principles that have led to the development of synthetic bivalent and tetravalent nAbs against SARS-CoV-2. The best nAb targets the host receptor binding site of the viral S-protein and its tetravalent versions can block entry with a potency that exceeds the bivalent nAbs by an order of magnitude. Structural studies show that both the bivalent and tetravalent nAbs can make multivalent interactions with a single S-protein trimer, observations consistent with the avidity and potency of these molecules. Significantly, we show that the tetravalent nAbs show much increased tolerance to potential virus escape mutants. Bivalent and tetravalent nAbs can be produced at large-scale and are as stable and specific as approved antibody drugs. Our results provide a general framework for developing potent antiviral therapies against COVID-19 and related viral threats, and our strategy can be readily applied to any antibody drug currently in development.
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3
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Gallo E, Kelil A, Bayliss PE, Jeganathan A, Egorova O, Ploder L, Adams JJ, Giblin P, Sidhu SS. In situ antibody phage display yields optimal inhibitors of integrin α11/β1. MAbs 2020; 12:1717265. [PMID: 31980006 PMCID: PMC6999838 DOI: 10.1080/19420862.2020.1717265] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 12/30/2019] [Accepted: 01/09/2020] [Indexed: 01/13/2023] Open
Abstract
Integrins are transmembrane multi-conformation receptors that mediate interactions with the extracellular matrix. In cancer, integrins influence metastasis, proliferation, and survival. Collagen-binding integrin-α11/β1, a marker of aggressive tumors that is involved in stroma-tumor crosstalk, may be an attractive target for anti-cancer therapeutic antibodies. We performed selections with phage-displayed synthetic antibody libraries for binding to either purified integrin-α11/β1 or in situ on live cells. The in-situ strategy yielded many diverse antibodies, and strikingly, most of these antibodies did not recognize purified integrin-α11/β1. Conversely, none of the antibodies selected for binding to purified integrin-α11/β1 were able to efficiently recognize native cell-surface antigen. Most importantly, only the in-situ selection yielded functional antibodies that were able to compete with collagen-I for binding to cell-surface integrin-α11/β1, and thus inhibited cell adhesion. In-depth characterization of a subset of in situ-derived clones as full-length immunoglobulins revealed high affinity cellular binding and inhibitory activities in the single-digit nanomolar range. Moreover, the antibodies showed high selectivity for integrin-α11/β1 with minimal cross-reactivity for close homologs. Taken together, our findings highlight the advantages of in-situ selections for generation of anti-integrin antibodies optimized for recognition and inhibition of native cell-surface proteins, and our work establishes general methods that could be extended to many other membrane proteins.
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Affiliation(s)
- Eugenio Gallo
- Department of Molecular Genetics, University of Toronto, Donnelly Centre, Toronto, Ontario, Canada
| | - Abdellali Kelil
- Department of Molecular Genetics, University of Toronto, Donnelly Centre, Toronto, Ontario, Canada
| | - Peter E. Bayliss
- Northern Biologics, Inc., Princess Margaret Cancer Research Tower, Toronto, Ontario, Canada
| | - Ajitha Jeganathan
- Northern Biologics, Inc., Princess Margaret Cancer Research Tower, Toronto, Ontario, Canada
| | - Olga Egorova
- Northern Biologics, Inc., Princess Margaret Cancer Research Tower, Toronto, Ontario, Canada
| | - Lynda Ploder
- Department of Molecular Genetics, University of Toronto, Donnelly Centre, Toronto, Ontario, Canada
| | - Jarret J. Adams
- Department of Molecular Genetics, University of Toronto, Donnelly Centre, Toronto, Ontario, Canada
| | - Patricia Giblin
- Northern Biologics, Inc., Princess Margaret Cancer Research Tower, Toronto, Ontario, Canada
| | - Sachdev S. Sidhu
- Department of Molecular Genetics, University of Toronto, Donnelly Centre, Toronto, Ontario, Canada
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4
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Chow RL, Snow B, Novak J, Looser J, Freund C, Vidgen D, Ploder L, McInnes RR. Vsx1, a rapidly evolving paired-like homeobox gene expressed in cone bipolar cells. Mech Dev 2001; 109:315-22. [PMID: 11731243 DOI: 10.1016/s0925-4773(01)00585-8] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The paired-like homeodomain (HD) protein Chx10 is distinguished by the presence of the CVC domain, a conserved 56 amino acid sequence C-terminal to the HD. In mammals, Chx10 is essential both for the proliferation of retinal progenitor cells and for the formation or survival of retinal bipolar interneurons. We describe the cloning and characterization of a mouse Chx10 homologue, Vsx1; phylogenetic analysis suggests that Vsx1 and its putative vertebrate orthologues have evolved rapidly. Vsx1 expression in the adult is predominantly retinal. Whereas Chx10 is expressed both in retinal progenitors in the developing eye and apparently in all bipolar cells of the mature retina, Vsx1 expression is first detected in the eye at postnatal day 5, where it is restricted to cone bipolar cells.
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Affiliation(s)
- R L Chow
- Program in Developmental Biology, The Research Institute, Hospital for Sick Children, 555 University Ave., Toronto, Ontario M5G 1X8, Canada
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5
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McInnes RR, Horsford DJ, Chow R, Ploder L, Percin EF, Yu JJ, Erclik T, Chow RL, Traboulsi E, Sarfarazi M, Kooy DVD, Lipshitz H. ABSTRACT homologues. Biochem Cell Biol 2000. [DOI: 10.1139/o00-041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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6
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Clarke G, Goldberg AF, Vidgen D, Collins L, Ploder L, Schwarz L, Molday LL, Rossant J, Szél A, Molday RS, Birch DG, McInnes RR. Rom-1 is required for rod photoreceptor viability and the regulation of disk morphogenesis. Nat Genet 2000; 25:67-73. [PMID: 10802659 DOI: 10.1038/75621] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The homologous membrane proteins Rom-1 and peripherin-2 are localized to the disk rims of photoreceptor outer segments (OSs), where they associate as tetramers and larger oligomers. Disk rims are thought to be critical for disk morphogenesis, OS renewal and the maintenance of OS structure, but the molecules which regulate these processes are unknown. Although peripherin-2 is known to be required for OS formation (because Prph2-/- mice do not form OSs; ref. 6), and mutations in RDS (the human homologue of Prph2) cause retinal degeneration, the relationship of Rom-1 to these processes is uncertain. Here we show that Rom1-/- mice form OSs in which peripherin-2 homotetramers are localized to the disk rims, indicating that peripherin-2 alone is sufficient for both disk and OS morphogenesis. The disks produced in Rom1-/- mice were large, rod OSs were highly disorganized (a phenotype which largely normalized with age) and rod photoreceptors died slowly by apoptosis. Furthermore, the maximal photoresponse of Rom1-/- rod photoreceptors was lower than that of controls. We conclude that Rom-1 is required for the regulation of disk morphogenesis and the viability of mammalian rod photoreceptors, and that mutations in human ROM1 may cause recessive photoreceptor degeneration.
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Affiliation(s)
- G Clarke
- Program in Developmental Biology, The Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
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7
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Xu S, Ladak R, Swanson DA, Soltyk A, Sun H, Ploder L, Vidgen D, Duncan AM, Garami E, Valle D, McInnes RR. PHR1 encodes an abundant, pleckstrin homology domain-containing integral membrane protein in the photoreceptor outer segments. J Biol Chem 1999; 274:35676-85. [PMID: 10585447 DOI: 10.1074/jbc.274.50.35676] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We cloned human and murine cDNAs of a gene (designated PHR1), expressed preferentially in retina and brain. In both species, PHR1 utilizes two promoters and alternative splicing to produce four PHR1 transcripts, encoding isoforms of 243, 224, 208, and 189 amino acids, each with a pleckstrin homology domain at their N terminus and a transmembrane domain at their C terminus. Transcript 1 originates from a 5'-photoreceptor-specific promoter with at least three Crx elements ((C/T)TAATCC). Transcript 2 originates from the same promoter but lacks exon 7, which encodes 35 amino acids immediately C-terminal to the pleckstrin homology domain. Transcripts 3 and 4 originate from an internal promoter in intron 2 and either include or lack exon 7, respectively. In situ hybridization shows that PHR1 is highly expressed in photoreceptors, with lower expression in retinal ganglion cells. Immunohistochemistry localizes the PHR1 protein to photoreceptor outer segments where chemical extraction studies confirm it is an integral membrane protein. Using a series of PHR1 glutathione S-transferase fusion proteins to perform in vitro binding assays, we found PHR1 binds transducin betagamma subunits but not inositol phosphates. This activity and subcellular location suggests that PHR1 may function as a previously unrecognized modulator of the phototransduction pathway.
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Affiliation(s)
- S Xu
- Predoctoral Training Program in Human Genetics, Department of Pediatrics, Baltimore, Maryland 21205, USA
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8
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Howell PL, Turner MA, Christodoulou J, Walker DC, Craig HJ, Simard LR, Ploder L, McInnes RR. Intragenic complementation at the argininosuccinate lyase locus: reconstruction of the active site. J Inherit Metab Dis 1998; 21 Suppl 1:72-85. [PMID: 9686346 DOI: 10.1023/a:1005361724967] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Intragenic complementation has been observed at the argininosuccinate lyase (ASL) locus and the ASL alleles in the ASL-deficient cell strains of two complementation phenotypes have been identified. The frequent complementers, strains that participate in the majority of the complementation events, were found to be either homozygous or heterozygous for the Q286R allele, while the high-activity complementers, those strains in which complementation is associated with a high restoration of activity, were found to be either homozygous or heterozygous for the D87G allele. Direct proof of the intragenic complementation observed at the ASL locus has been obtained with the co-expression of the D87G and Q286R alleles in COS cells. A significant increase in the ASL activity was observed when the two alleles were co-expressed relative to the expression of each mutant allele alone. The increase in activity was comparable to that observed previously in the fibroblast complementation studies. The structure determinations of ASL and the homologous eye lens protein, duck delta II crystallin, have revealed that the active site of ASL is made up of residues from three different monomers. The structural mapping of the Q286 and D87 residues shows that both are located near the active site but that, in any one active site, each is contributed by a different monomer. The molecular symmetry of the ASL protein is such that when mutant monomers combine randomly, one active site will contain both mutations and at least one active site will contain no mutations at all. It is these 'native' active sites in the hybrid Q286R/D87G proteins that give rise to the partial recovery of enzymatic activity observed during intragenic complementation.
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Affiliation(s)
- P L Howell
- Division of Biochemistry Research, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
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9
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Freund CL, Gregory-Evans CY, Furukawa T, Papaioannou M, Looser J, Ploder L, Bellingham J, Ng D, Herbrick JA, Duncan A, Scherer SW, Tsui LC, Loutradis-Anagnostou A, Jacobson SG, Cepko CL, Bhattacharya SS, McInnes RR. Cone-rod dystrophy due to mutations in a novel photoreceptor-specific homeobox gene (CRX) essential for maintenance of the photoreceptor. Cell 1997; 91:543-53. [PMID: 9390563 DOI: 10.1016/s0092-8674(00)80440-7] [Citation(s) in RCA: 380] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Genes associated with inherited retinal degeneration have been found to encode proteins required for phototransduction, metabolism, or structural support of photoreceptors. Here we show that mutations in a novel photoreceptor-specific homeodomain transcription factor gene (CRX) cause an autosomal dominant form of cone-rod dystrophy (adCRD) at the CORD2 locus on chromosome 19q13. In affected members of a CORD2-linked family, the highly conserved glutamic acid at the first position of the recognition helix is replaced by alanine (E80A). In another CRD family, a 1 bp deletion (E168 [delta1 bp]) within a novel sequence, the WSP motif, predicts truncation of the C-terminal 132 residues of CRX. Mutations in the CRX gene cause adCRD either by haploinsufficiency or by a dominant negative effect and demonstrate that CRX is essential for the maintenance of mammalian photoreceptors.
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Affiliation(s)
- C L Freund
- Department of Genetics, The Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
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10
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Belecky-Adams T, Tomarev S, Li HS, Ploder L, McInnes RR, Sundin O, Adler R. Pax-6, Prox 1, and Chx10 homeobox gene expression correlates with phenotypic fate of retinal precursor cells. Invest Ophthalmol Vis Sci 1997; 38:1293-303. [PMID: 9191592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
PURPOSE To study the expression patterns of the homeobox genes Pax-6, Prox 1, and Chx10 during chick retinal development in vivo and in vitro. METHODS Sections of paraformaldehyde-fixed, paraffin-embedded eyes were obtained at a range of developmental stages. In situ hybridization was carried out on tissue sections using digoxigenin-labeled sense and antisense RNA probes that recognize chicken Pax-6 and Prox 1 (whose sequences were already available), and chicken Chx10 (which was cloned and sequenced as part of this study). Selected developmental stages were also studied by immunocytochemistry with antibodies against Pax-6 and Prox 1, and by Northern blot analysis using 32P-labeled probes. RESULTS Until embryonic day (ED) 5, in situ hybridization shows widespread, diffuse distribution of all three genes. Between ED 6 and ED 8, however, they acquire distinct, topographically specific patterns of expression. The Prox 1 signal is predominantly expressed in the prospective horizontal cell layer of the neuroepithelium, decreases vitreally, and is absent from ganglion cells and the prospective photoreceptor layer. Pax-6 is strongly expressed only in the prospective ganglion-cell and amacrine-cell regions at the same stages, and is not detected in prospective photoreceptors. Chx10 expression becomes concentrated in the future bipolar-cell region of the inner nuclear layer. Similar patterns are maintained by ED 15 through ED 18, after cell differentiation has taken place. Pax-6 and Prox 1 immunoreactive materials showed nuclear localization and a pattern of laminar distribution equivalent to that seen by in situ hybridization. CONCLUSIONS These results suggest that the differentiated fate of retinal precursor cells may be influenced by Pax-6, Prox 1, or Chx10, this hypothesis is now being tested using dissociated chick embryo retinal cell cultures.
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Affiliation(s)
- T Belecky-Adams
- Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-9257, USA
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11
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Swanson DA, Freund CL, Steel JM, Xu S, Ploder L, McInnes RR, Valle D. A differential hybridization scheme to identify photoreceptor-specific genes. Genome Res 1997; 7:513-21. [PMID: 9149946 DOI: 10.1101/gr.7.5.513] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Identification of genes expressed preferentially or exclusively in photoreceptors will facilitate the understanding of photoreceptor biology as well as provide candidate genes for inherited retinal degenerations. To achieve this goal we performed a differential hybridization screen of 3717 well-isolated phage clones from a human retinal cDNA library. Clones were selected for further study if they hybridized exclusively or strongly preferentially to a probe derived from RNA isolated from the cone-predominant retina of 13-line ground squirrels as compared to a probe derived from human fibroblast RNA. Twenty percent of clones (9/45) identified by this screen were derived from photoreceptor-specific genes and an additional 24.4% (11/45) were from neural-specific genes, demonstrating the utility of this strategy in identifying genes important for retinal biology.
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Affiliation(s)
- D A Swanson
- Predoctoral Training Program in Human Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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12
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Walker DC, Christodoulou J, Craig HJ, Simard LR, Ploder L, Howell PL, McInnes RR. Intragenic complementation at the human argininosuccinate lyase locus. Identification of the major complementing alleles. J Biol Chem 1997; 272:6777-83. [PMID: 9045711 DOI: 10.1074/jbc.272.10.6777] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
To determine the molecular and biochemical basis of intragenic complementation observed at the human argininosuccinate lyase (ASL) locus, we identified the ASL alleles in ASL-deficient cell strains with two unique complementation phenotypes: (i) frequent complementers, strains that participated in the majority of complementation events, and (ii) high activity complementers, strains in which complementation was associated with a relatively high level of restoration of ASL activity. Four mutations (Q286R, D87G, A398D, and a deletion of exon 13) were identified in the four strains examined. One of the two frequent complementers was homozygous, and the other heterozygous, for the Q286R allele. Similarly, one of the two high activity complementers was homozygous, and the other heterozygous, for the D87G allele. When the Q286R and D87G mutations were introduced by site-directed mutagenesis into wild-type ASL cDNA, each conferred loss of ASL activity in COS cell transfection assays. To test directly the hypothesis that intragenic complementation occurs at the ASL locus, one of the major complementation events observed previously, between strains carrying the Q286R and D87G alleles, was reconstructed in COS cell transfection assays. A partial restoration of ASL activity, comparable with the increase seen in the fibroblast complementation analysis, was observed on joint cotransfection of these two alleles. The results provide molecular confirmation of the major features of the ASL mutant complementation map, identify the Q286R and D87D alleles as the frequent and high activity complementing alleles, respectively, and provide direct proof of intragenic complementation at the ASL locus.
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Affiliation(s)
- D C Walker
- Department of Genetics, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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13
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Swanson DA, Freund CL, Ploder L, McInnes RR, Valle D. A ubiquitin C-terminal hydrolase gene on the proximal short arm of the X chromosome: implications for X-linked retinal disorders. Hum Mol Genet 1996; 5:533-8. [PMID: 8845848 DOI: 10.1093/hmg/5.4.533] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We report the cloning of a novel human cDNA which encodes a 690 amino acid protein with high homology to ubiquitin C-terminal hydrolases. Northern blot analysis shows expression of a 3.3 kb transcript in all tissues examined, with 5- to 10-fold higher levels in retina than elsewhere. We mapped the structural gene to Xp21.2-p11.2. This gene's relatively high levels of retinal expression and recent work showing that perturbations in protein turnover and processing can lead to retinal disease make it an excellent candidate for several X-linked retinal disorders mapping within this interval. Additionally, there is evidence that members of the ubiquitin hydrolase family may play a role in oncogenesis and a locus implicated in ovarian cancer is also located within this region.
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Affiliation(s)
- D A Swanson
- Predoctoral Training Program in Human Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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14
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Burmeister M, Novak J, Liang MY, Basu S, Ploder L, Hawes NL, Vidgen D, Hoover F, Goldman D, Kalnins VI, Roderick TH, Taylor BA, Hankin MH, McInnes RR. Ocular retardation mouse caused by Chx10 homeobox null allele: impaired retinal progenitor proliferation and bipolar cell differentiation. Nat Genet 1996; 12:376-84. [PMID: 8630490 DOI: 10.1038/ng0496-376] [Citation(s) in RCA: 397] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Ocular retardation (or) is a murine eye mutation causing microphthalmia, a thin hypocellular retina and optic nerve aplasia. Here we show that mice carrying the OrJ allele have a premature stop codon in the homeobox of the Chx10 gene, a gene expressed at high levels in uncommitted retinal progenitor cells and mature bipolar cells. No CHX10 protein was detectable in the retinal neuroepithelium of orJ homozygotes. The loss of CHX10 leads both to reduced proliferation of retinal progenitors and to a specific absence of differentiated bipolar cells. Other major retinal cell types were present and correctly positioned in the mutant retina, although rod outer segments were short and retinal lamination was incomplete. These results indicate that Chx10 is an essential component in the network of genes required for the development of the mammalian eye, with profound effects on retinal progenitor proliferation and bipolar cell specification or differentiation. off
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Affiliation(s)
- M Burmeister
- Mental Health Research Institute, University of Michigan, Ann Arbor 48109-0720, USA
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15
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Liu IS, Chen JD, Ploder L, Vidgen D, van der Kooy D, Kalnins VI, McInnes RR. Developmental expression of a novel murine homeobox gene (Chx10): evidence for roles in determination of the neuroretina and inner nuclear layer. Neuron 1994; 13:377-93. [PMID: 7914735 DOI: 10.1016/0896-6273(94)90354-9] [Citation(s) in RCA: 302] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Few potential regulatory proteins of vertebrate retinal development have been identified. We describe a 39 kDa murine polypeptide (Chx10) with a homeodomain 82% identical to that of the nematode protein ceh-10. In the developing mouse, the Chx10 transcript is expressed throughout the anterior optic vesicle and all neuroblasts of the optic cup. In the mature retina, the Chx10 protein is restricted to the inner nuclear layer, in which its expression decreases from the outer to the inner margin. Chx10 transcripts are also detected in regions of the developing thalamus, hindbrain, and ventral spinal cord. The data suggest that Chx10 plays critical roles in the formation of the neuroretina and in the development and maintenance of the inner nuclear layer.
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Affiliation(s)
- I S Liu
- Department of Genetics, Hospital for Sick Children, Toronto, Ontario, Canada
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