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Thuma TBT, Procopio RA, Jimenez HJ, Gunton KB, Pulido JS. Hypomorphic variants in inherited retinal and ocular diseases: A review of the literature with clinical cases. Surv Ophthalmol 2024; 69:337-348. [PMID: 38036193 DOI: 10.1016/j.survophthal.2023.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 11/17/2023] [Accepted: 11/20/2023] [Indexed: 12/02/2023]
Abstract
Hypomorphic variants decrease, but do not eliminate, gene function via a reduction in the amount of mRNA or protein product produced by a gene or by production of a gene product with reduced function. Many hypomorphic variants have been implicated in inherited retinal diseases (IRDs) and other genetic ocular conditions; however, there is heterogeneity in the use of the term "hypomorphic" in the scientific literature. We searched for all hypomorphic variants reported to cause IRDs and ocular disorders. We also discuss the presence of hypomorphic variants in the patient population of our ocular genetics department over the past decade. We propose that standardized criteria should be adopted for use of the term "hypomorphic" to describe gene variants to improve genetic counseling and patient care outcomes.
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Affiliation(s)
- Tobin B T Thuma
- Department of Pediatric Ophthalmology and Strabismus, Wills Eye Hospital, Philadelphia, PA, USA
| | | | - Hiram J Jimenez
- Vickie and Jack Farber Vision Research Center, Wills Eye Hospital, Philadelphia, PA, USA
| | - Kammi B Gunton
- Department of Pediatric Ophthalmology and Strabismus, Wills Eye Hospital, Philadelphia, PA, USA
| | - Jose S Pulido
- Vickie and Jack Farber Vision Research Center, Wills Eye Hospital, Philadelphia, PA, USA; Retina Service, Wills Eye Hospital, Philadelphia, PA, USA.
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Bravo L, Pereyra KV, Diaz HS, Flores M, Schwarz KG, Toledo C, Díaz-Jara E, González L, Andia ME, Del Rio R. Enhanced Peripheral Chemoreflex Drive Is Associated with Cardiorespiratory Disorders in Mice with Coronary Heart Disease. Adv Exp Med Biol 2023; 1427:99-106. [PMID: 37322340 DOI: 10.1007/978-3-031-32371-3_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Coronary heart disease (CHD) is a prevalent cardiovascular disease characterized by coronary artery blood flow reductions caused by lipid deposition and oxidation within the coronary arteries. Dyslipidemia is associated with local tissue damage by oxidative stress/inflammation and carotid bodies (CB) peripheral chemoreceptors are heavily modulated by both reactive oxygen species and pro-inflammatory molecules (i.e., cytokines). Despite this, it is not know whether CB-mediated chemoreflex drive may be affected in CHD. In the present study, we evaluated peripheral CB-mediated chemoreflex drive, cardiac autonomic function, and the incidence of breathing disorders in a murine model of CHD. Compared to age-matched control mice, CHD mice showed enhanced CB-chemoreflex drive (twofold increase in the hypoxic ventilatory response), cardiac sympathoexcitation, and irregular breathing disorders. Remarkably, all these were closely linked to the enhanced CB-mediated chemoreflex drive. Our results showed that mice with CHD displayed an enhanced CB chemoreflex, sympathoexcitation, and disordered breathing and suggest that CBs may be involved in chronic cardiorespiratory alterations in the setting of CHD.
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Affiliation(s)
- Liena Bravo
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Katherin V Pereyra
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Hugo S Diaz
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Mariajosé Flores
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Karla G Schwarz
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Camilo Toledo
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Esteban Díaz-Jara
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Leticia González
- Radiology Department & ANID - Millennium Institute for Intelligent Healthcare Engineering - iHEALTH, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Marcelo E Andia
- Radiology Department & ANID - Millennium Institute for Intelligent Healthcare Engineering - iHEALTH, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile.
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile.
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Thompson JA, Chiang JPW, De Roach JN, McLaren TL, Chen FK, Hoffmann L, Campbell I, Lamey TM. Analysis of the ABCA4 c.[2588G>C;5603A>T] Allele in the Australian Population. Adv Exp Med Biol 2019; 1185:269-273. [PMID: 31884623 DOI: 10.1007/978-3-030-27378-1_44] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Inherited retinal diseases (IRDs) are genetically and phenotypically diverse, and they cause significant morbidity worldwide. Importantly, IRDs may be amenable to precision medicine strategies, and thus the molecular characterisation of causative variants is becoming increasingly important with the promise of personalised therapies on the horizon. ABCA4, involved in the translocation of visual cycle derivatives, is a well-established, frequent cause of IRDs worldwide, with pathogenic variants implicated in phenotypically diverse diseases. Identification of causative ABCA4 variants in some individuals, however, has been enigmatic, and resolution of this issue is currently a hotbed of research. Recent evidence has indicated that hypomorphic alleles, which cause disease under certain conditions, may account for some of the missing causal variants. It has been postulated that the ABCA4 c.5603A>T (p.Asn1868Ile) variant, previously considered benign, be reclassified as hypomorphic when in cis configuration with c.2588G>C (p.Gly863Ala/Gly863del), a variant previously considered to be pathogenic in its own right. We are exploring this relationship within an Australian cohort to test this theory.
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Affiliation(s)
- Jennifer A Thompson
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, WA, Australia.
| | | | - John N De Roach
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, WA, Australia.,Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, WA, Australia
| | - Terri L McLaren
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, WA, Australia.,Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, WA, Australia
| | - Fred K Chen
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, WA, Australia.,Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, WA, Australia.,Ocular Tissue Engineering Laboratory, Lions Eye Institute, Perth, WA, Australia.,Department of Ophthalmology, Royal Perth Hospital, Perth, WA, Australia
| | - Ling Hoffmann
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, WA, Australia
| | - Isabella Campbell
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, WA, Australia
| | - Tina M Lamey
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, WA, Australia.,Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, WA, Australia
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Lee PP, Woodbine L, Gilmour KC, Bibi S, Cale CM, Amrolia PJ, Veys PA, Davies EG, Jeggo PA, Jones A. The many faces of Artemis-deficient combined immunodeficiency - Two patients with DCLRE1C mutations and a systematic literature review of genotype-phenotype correlation. Clin Immunol 2013; 149:464-74. [PMID: 24230999 DOI: 10.1016/j.clim.2013.08.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 08/04/2013] [Accepted: 08/07/2013] [Indexed: 12/31/2022]
Abstract
Defective V(D)J recombination and DNA double-strand break (DSB) repair severely impair the development of T-lymphocytes and B-lymphocytes. Most patients manifest a severe combined immunodeficiency during infancy. We report 2 siblings with combined immunodeficiency (CID) and immunodysregulation caused by compound heterozygous Artemis mutations, including an exon 1-3 deletion generating a null allele, and a missense change (p.T71P). Skin fibroblasts demonstrated normal DSB repair by gamma-H2AX analysis, supporting the predicted hypomorphic nature of the p.T71P allele. In addition to these two patients, 12 patients with Artemis-deficient CID were previously reported. All had significant morbidities including recurrent infections, autoimmunity, EBV-associated lymphoma, and carcinoma despite having hypomorphic mutants with residual Artemis expression, V(D)J recombination or DSB repair capacity. Nine patients underwent stem cell transplant and six survived, while four patients who did not receive transplant died. The progressive nature of immunodeficiency and genomic instability accounts for poor survival, and early HSCT should be considered.
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Affiliation(s)
- Pamela P Lee
- Department of Immunology, Great Ormond Street Hospital NHS Foundation Trust, London, UK
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Goring ME, Leibovitch M, Gea-Mallorqui E, Karls S, Richard F, Hanic-Joyce PJ, Joyce PBM. The ability of an arginine to tryptophan substitution in Saccharomyces cerevisiae tRNA nucleotidyltransferase to alleviate a temperature-sensitive phenotype suggests a role for motif C in active site organization. Biochim Biophys Acta 2013; 1834:2097-106. [PMID: 23872483 DOI: 10.1016/j.bbapap.2013.07.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 07/08/2013] [Accepted: 07/10/2013] [Indexed: 11/15/2022]
Abstract
We report that the temperature-sensitive (ts) phenotype in Saccharomyces cerevisiae associated with a variant tRNA nucleotidyltransferase containing an amino acid substitution at position 189 results from a reduced ability to incorporate AMP and CMP into tRNAs. We show that this defect can be compensated for by a second-site suppressor converting residue arginine 64 to tryptophan. The R64W substitution does not alter the structure or thermal stability of the enzyme dramatically but restores catalytic activity in vitro and suppresses the ts phenotype in vivo. R64 is found in motif A known to be involved in catalysis and nucleotide triphosphate binding while E189 lies within motif C previously thought only to connect the head and neck domains of the protein. Although mutagenesis experiments indicate that residues R64 and E189 do not interact directly, our data suggest a critical role for residue E189 in enzyme structure and function. Both R64 and E189 may contribute to the organization of the catalytic domain of the enzyme. These results, along with overexpression and deletion analyses, show that the ts phenotype of cca1-E189F does not arise from thermal instability of the variant tRNA nucleotidyltransferase but instead from the inability of a partially active enzyme to support growth only at higher temperatures.
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Affiliation(s)
- Mark E Goring
- Department of Biology, Concordia University, Montréal, H4B 1R6, Canada
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