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De Nittis P, Efthymiou S, Sarre A, Guex N, Chrast J, Putoux A, Sultan T, Raza Alvi J, Ur Rahman Z, Zafar F, Rana N, Rahman F, Anwar N, Maqbool S, Zaki MS, Gleeson JG, Murphy D, Galehdari H, Shariati G, Mazaheri N, Sedaghat A, Lesca G, Chatron N, Salpietro V, Christoforou M, Houlden H, Simonds WF, Pedrazzini T, Maroofian R, Reymond A. Inhibition of G-protein signalling in cardiac dysfunction of intellectual developmental disorder with cardiac arrhythmia (IDDCA) syndrome. J Med Genet 2021; 58:815-831. [PMID: 33172956 PMCID: PMC8639930 DOI: 10.1136/jmedgenet-2020-107015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 08/30/2020] [Accepted: 09/04/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND Pathogenic variants of GNB5 encoding the β5 subunit of the guanine nucleotide-binding protein cause IDDCA syndrome, an autosomal recessive neurodevelopmental disorder associated with cognitive disability and cardiac arrhythmia, particularly severe bradycardia. METHODS We used echocardiography and telemetric ECG recordings to investigate consequences of Gnb5 loss in mouse. RESULTS We delineated a key role of Gnb5 in heart sinus conduction and showed that Gnb5-inhibitory signalling is essential for parasympathetic control of heart rate (HR) and maintenance of the sympathovagal balance. Gnb5-/- mice were smaller and had a smaller heart than Gnb5+/+ and Gnb5+/- , but exhibited better cardiac function. Lower autonomic nervous system modulation through diminished parasympathetic control and greater sympathetic regulation resulted in a higher baseline HR in Gnb5-/- mice. In contrast, Gnb5-/- mice exhibited profound bradycardia on treatment with carbachol, while sympathetic modulation of the cardiac stimulation was not altered. Concordantly, transcriptome study pinpointed altered expression of genes involved in cardiac muscle contractility in atria and ventricles of knocked-out mice. Homozygous Gnb5 loss resulted in significantly higher frequencies of sinus arrhythmias. Moreover, we described 13 affected individuals, increasing the IDDCA cohort to 44 patients. CONCLUSIONS Our data demonstrate that loss of negative regulation of the inhibitory G-protein signalling causes HR perturbations in Gnb5-/- mice, an effect mainly driven by impaired parasympathetic activity. We anticipate that unravelling the mechanism of Gnb5 signalling in the autonomic control of the heart will pave the way for future drug screening.
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Affiliation(s)
| | - Stephanie Efthymiou
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Alexandre Sarre
- Cardiovascular Assessment Facility, University of Lausanne, Lausanne, Switzerland
| | - Nicolas Guex
- Bioinformatics Competence Center, University of Lausanne, Lausanne, Switzerland
| | - Jacqueline Chrast
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Audrey Putoux
- Service de Génétique, Hopital Femme Mere Enfant, Bron, France
| | - Tipu Sultan
- Department of Pediatric Neurology, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Javeria Raza Alvi
- Department of Pediatric Neurology, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Zia Ur Rahman
- Department of Pediatric Neurology, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Faisal Zafar
- Department of Paediatric Neurology, Children's Hospital and Institute of Child Health, Multan, Pakistan
| | - Nuzhat Rana
- Department of Paediatric Neurology, Children's Hospital and Institute of Child Health, Multan, Pakistan
| | - Fatima Rahman
- Department of Developmental-Behavioural Paediatrics, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Najwa Anwar
- Department of Developmental-Behavioural Paediatrics, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Shazia Maqbool
- Department of Developmental-Behavioural Paediatrics, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Joseph G Gleeson
- Department of Neuroscience and Pediatrics, Howard Hughes Medical Institute, La Jolla, California, USA
| | - David Murphy
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Hamid Galehdari
- Department of Genetics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahwaz, Iran (the Islamic Republic of)
| | - Gholamreza Shariati
- Department of Medical Genetics, Faculty of Medicine, Ahvaz Jondishapour University of Medical Sciences, Ahvaz, Iran (the Islamic Republic of)
| | - Neda Mazaheri
- Department of Genetics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahwaz, Iran (the Islamic Republic of)
| | - Alireza Sedaghat
- Health Research Institute, Diabetes Research Center, Ahvaz Jundishapur University of medical Sciences, Ahvaz, Iran (the Islamic Republic of)
| | - Gaetan Lesca
- Service de Genetique, Hospices Civils de Lyon, Lyon, France
| | - Nicolas Chatron
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
- Service de Genetique, Hospices Civils de Lyon, Lyon, France
| | - Vincenzo Salpietro
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Marilena Christoforou
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Henry Houlden
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - William F Simonds
- Metabolic Diseases Branch/NIDDK, National Institutes of Health, Bethesda, MD, USA
| | - Thierry Pedrazzini
- Experimental Cardiology Unit, Department of Cardiovascular Medicine, University of Lausanne, Lausanne, Switzerland
| | - Reza Maroofian
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Alexandre Reymond
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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Jiang X, Mahroo OA. Negative electroretinograms: genetic and acquired causes, diagnostic approaches and physiological insights. Eye (Lond) 2021; 35:2419-2437. [PMID: 34127841 PMCID: PMC8377097 DOI: 10.1038/s41433-021-01604-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/05/2021] [Accepted: 05/10/2021] [Indexed: 02/07/2023] Open
Abstract
The dark-adapted human electroretinogram (ERG) response to a standard bright flash includes a negative-going a-wave followed by a positive-going b-wave that crosses the baseline. An electronegative waveform (or negative ERG) results when the b-wave is selectively reduced such that the ERG fails to cross the baseline following the a-wave. In the context of a normally sized a-wave, it indicates a site of retinal dysfunction occurring after phototransduction (commonly at the photoreceptor to bipolar cell synapse). This is an important finding. In genetic disease, the pattern of ERG abnormality can point to variants in a small group of genes (frequently those associated with congenital stationary night blindness and X-linked retinoschisis, but negative ERGs can also be seen in other conditions including syndromic disease). In acquired disease, there are numerous causes, but specific features may point to melanoma-associated retinopathy (MAR). In some cases, the visual symptoms precede the diagnosis of the melanoma and so the ERG findings can initiate investigations facilitating early detection and treatment. Negative ERGs can occur in other paraneoplastic conditions, and in a range of other diseases. This review will outline the physiological basis for the negative ERG, report prevalences in the literature from different cohorts, discuss the range of causes, displaying examples of a number of ERG phenotypes, highlight features of a clinical approach to patients, and briefly discuss further insights relating to current flows shaping the a-wave trough and from single-cell transcriptome analysis.
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Affiliation(s)
- Xiaofan Jiang
- grid.83440.3b0000000121901201Institute of Ophthalmology, University College London, London, UK ,grid.439257.e0000 0000 8726 5837Retinal and Genetics Services, Moorfields Eye Hospital, London, UK ,grid.425213.3Section of Ophthalmology and Department of Twin Research and Genetic Epidemiology, King’s College London, St Thomas’ Hospital Campus, London, UK
| | - Omar A. Mahroo
- grid.83440.3b0000000121901201Institute of Ophthalmology, University College London, London, UK ,grid.439257.e0000 0000 8726 5837Retinal and Genetics Services, Moorfields Eye Hospital, London, UK ,grid.425213.3Section of Ophthalmology and Department of Twin Research and Genetic Epidemiology, King’s College London, St Thomas’ Hospital Campus, London, UK ,grid.5335.00000000121885934Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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Extended Phenotyping and Functional Validation Facilitate Diagnosis of a Complex Patient Harboring Genetic Variants in MCCC1 and GNB5 Causing Overlapping Phenotypes. Genes (Basel) 2021; 12:genes12091352. [PMID: 34573334 PMCID: PMC8469011 DOI: 10.3390/genes12091352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 08/26/2021] [Accepted: 08/26/2021] [Indexed: 12/22/2022] Open
Abstract
Identifying multiple ultra-rare genetic syndromes with overlapping phenotypes is a diagnostic conundrum in clinical genetics. This study investigated the pathogenicity of a homozygous missense variant in GNB5 (GNB5L; NM_016194.4: c.920T > G (p. Leu307Arg); GNB5S; NM_006578.4: c.794T > G (p. Leu265Arg)) identified through exome sequencing in a female child who also had 3-methylcrotonyl-CoA carboxylase (3-MCC) deficiency (newborn screening positive) and hemoglobin E trait. The proband presented with early-onset intellectual disability, the severity of which was more in keeping with GNB5-related disorder than 3-MCC deficiency. She later developed bradycardia and cardiac arrest, and upon re-phenotyping showed cone photo-transduction recovery deficit, all known only to GNB5-related disorders. Patient-derived fibroblast assays showed preserved GNB5S expression, but bioluminescence resonance energy transfer assay showed abolished function of the variant reconstituted Gβ5S containing RGS complexes for deactivation of D2 dopamine receptor activity, confirming variant pathogenicity. This study highlights the need for precise phenotyping and functional assays to facilitate variant classification and clinical diagnosis in patients with complex medical conditions.
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Sciacca FL, Ciaccio C, Fontana F, Strano C, Gilardoni F, Pantaleoni C, D'Arrigo S. Severe Phenotype in a Patient With Homozygous 15q21.2 Microdeletion Involving BCL2L10, GNB5, and MYO5C Genes, Resembling Infantile Developmental Disorder With Cardiac Arrhythmias (IDDCA). Front Genet 2020; 11:399. [PMID: 32477400 PMCID: PMC7237723 DOI: 10.3389/fgene.2020.00399] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 03/30/2020] [Indexed: 11/29/2022] Open
Abstract
Homozygous and compound heterozygous mutations in GNB5 gene have been associated with a wide spectrum of clinical presentations, ranging from neurodevelopmental issues with or without cardiac arrhythmia (LADCI) to severe developmental delay with epileptic encephalopathy, retinal dystrophy, and heart rhythm abnormalities (IDDCA). While missense or missense/non-sense mutations usually lead to milder form, the biallelic loss of function of GNB5 gene causes the severe multisystemic IDDCA phenotype. So far, only 27 patients have been described with GNB5-associated disease. We report the first case of a patient carrying a homozygous 15q21.2 microdeletion, encompassing GNB5 and the two contiguous genes BCL2L10 and MYO5C. The clinical features of the child are consistent with the severe IDDCA phenotype, thus confirming the GNB5 loss-of-function mechanism in determining such presentation of the disease.
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Affiliation(s)
- Francesca L Sciacca
- Neurological Biochemistry and Neuropharmacology Unit, Laboratory of Cytogenetic, Department of Diagnostic and Technology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Claudia Ciaccio
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Federica Fontana
- Neurological Biochemistry and Neuropharmacology Unit, Laboratory of Cytogenetic, Department of Diagnostic and Technology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Camilla Strano
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Francesca Gilardoni
- Neurological Biochemistry and Neuropharmacology Unit, Laboratory of Cytogenetic, Department of Diagnostic and Technology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Chiara Pantaleoni
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Stefano D'Arrigo
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
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Yazdani S, Badjatiya A, Dorrani N, Lee H, Grody WW, Nelson SF, Dipple KM. Genetic characterization and long-term management of severely affected siblings with intellectual developmental disorder with cardiac arrhythmia syndrome. Mol Genet Metab Rep 2020; 23:100582. [PMID: 32280589 PMCID: PMC7138921 DOI: 10.1016/j.ymgmr.2020.100582] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/19/2020] [Accepted: 03/21/2020] [Indexed: 11/30/2022] Open
Abstract
We report two brothers with severe global cognitive and motor delay, cortical visual impairment and sick sinus syndrome who were born to consanguineous parents. Standard genetic evaluations did not reveal the cause of their mental retardation. As expected, chromosomal microarray (CMA) revealed extensive regions of homozygosity. Exome sequencing revealed that both affected boys were homozygous for a nonsense mutation in the G-protein β5 (GNB5) gene (NM_016194.3:c.1032C > G; Tyr344Ter), and that the parents were carriers of this mutation. No other DNA variants that were explanatory for the sick sinus or the developmental delay/intellectual disability were identified, and no other clinical parameters are likely to have contributed to this unusual combination of phenotypes. The neurologic features of our patients are more severe than those of most of the other patients previously reported with GNB5 variants, probably because of the homozygous, complete loss-of-function (nonsense/stop-gain) nature of their variant, and their clinical course has been monitored for longer duration.
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Affiliation(s)
- Shahram Yazdani
- Departments of Pediatrics and Mattel Children's Hospital at UCLA, Los Angeles, CA, United States of America
| | - Anish Badjatiya
- Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America
| | - Naghmeh Dorrani
- Departments of Pediatrics and Mattel Children's Hospital at UCLA, Los Angeles, CA, United States of America
| | - Hane Lee
- Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America.,Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America
| | - Wayne W Grody
- Departments of Pediatrics and Mattel Children's Hospital at UCLA, Los Angeles, CA, United States of America.,Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America.,Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America
| | - Stanley F Nelson
- Departments of Pediatrics and Mattel Children's Hospital at UCLA, Los Angeles, CA, United States of America.,Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America.,Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America
| | - Katrina M Dipple
- Departments of Pediatrics and Mattel Children's Hospital at UCLA, Los Angeles, CA, United States of America.,Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America
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Tang M, Wang Y, Xu Y, Tong W, Jin D, Yang XA. IDDCA syndrome in a Chinese infant due to GNB5 biallelic mutations. J Hum Genet 2020; 65:627-631. [PMID: 32203251 DOI: 10.1038/s10038-020-0742-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 03/02/2020] [Accepted: 03/02/2020] [Indexed: 11/10/2022]
Abstract
Herein, we present a Chinese infant with an early-onset intellectual developmental disorder with cardiac arrhythmia syndrome. A 6-month-old boy visited our hospital because of convulsions and paroxysmal cyanosis for 1 day. Mental development analysis showed that the patient had a neurodevelopmental delay. Frequent seizures occurred, and ECG monitoring demonstrated severe cardiac arrhythmia. Whole-exome sequencing showed that the infant had two compound heterozygous variants, NM_016194:c.458G>A/p.Cys153Tyr and NM_016194:c.1032C>A/p.Tyr344*, in GNB5. The first variant was inherited from his mother, while the other one was a de novo variant. Haplotype analysis indicated that the de novo variant was located in the paternal chromosome. Structural modeling indicated that both mutations could influence the interaction of GNB5 with its binding protein. Our study expanded the known genetic and phenotypic spectrum of GNB5-associated diseases, by presenting a Chinese male infant with IDDCA.
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Affiliation(s)
- Mingxing Tang
- Pediatric Intensive Care Unit, Anhui Provincial Children's Hospital, Hefei, 230029, PR China
| | - Yajian Wang
- Beijing Chigene Translational Medicine Research Center Co., Ltd, Beijing, 100875, PR China
| | - Yuanyuan Xu
- Pediatric Intensive Care Unit, Anhui Provincial Children's Hospital, Hefei, 230029, PR China
| | - Wenjia Tong
- Pediatric Intensive Care Unit, Anhui Provincial Children's Hospital, Hefei, 230029, PR China
| | - Danqun Jin
- Pediatric Intensive Care Unit, Anhui Provincial Children's Hospital, Hefei, 230029, PR China.
| | - Xiu-An Yang
- School of Basic Medical Science, Chengde Medical University, Chengde, 067000, PR China.
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The Emerging Role of Gβ Subunits in Human Genetic Diseases. Cells 2019; 8:cells8121567. [PMID: 31817184 PMCID: PMC6952978 DOI: 10.3390/cells8121567] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 11/23/2019] [Accepted: 11/29/2019] [Indexed: 12/20/2022] Open
Abstract
Environmental stimuli are perceived and transduced inside the cell through the activation of signaling pathways. One common type of cell signaling transduction network is initiated by G-proteins. G-proteins are activated by G-protein-coupled receptors (GPCRs) and transmit signals from hormones, neurotransmitters, and other signaling factors, thus controlling a number of biological processes that include synaptic transmission, visual photoreception, hormone and growth factors release, regulation of cell contraction and migration, as well as cell growth and differentiation. G-proteins mainly act as heterotrimeric complexes, composed of alpha, beta, and gamma subunits. In the last few years, whole exome sequencing and biochemical studies have shown causality of disease-causing variants in genes encoding G-proteins and human genetic diseases. This review focuses on the G-protein β subunits and their emerging role in the etiology of genetically inherited rare diseases in humans.
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