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Donkó Á, Sharapova SO, Kabat J, Ganesan S, Hauck FH, Bergerson JRE, Marois L, Abbott J, Moshous D, Williams KW, Campbell N, Martin PL, Lagresle-Peyrou C, Trojan T, Kuzmenko NB, Deordieva EA, Raykina EV, Abers MS, Abolhassani H, Barlogis V, Milla C, Hall G, Mousallem T, Church J, Kapoor N, Cros G, Chapdelaine H, Franco-Jarava C, Lopez-Lerma I, Miano M, Leiding JW, Klein C, Stasia MJ, Fischer A, Hsiao KC, Martelius T, Sepännen MRJ, Barmettler S, Walter J, Masmas TN, Mukhina AA, Falcone EL, Kracker S, Shcherbina A, Holland SM, Leto TL, Hsu AP. Clinical and functional spectrum of RAC2-related immunodeficiency. Blood 2024; 143:1476-1487. [PMID: 38194689 PMCID: PMC11033590 DOI: 10.1182/blood.2023022098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 12/01/2023] [Accepted: 12/12/2023] [Indexed: 01/11/2024] Open
Abstract
ABSTRACT Mutations in the small Rho-family guanosine triphosphate hydrolase RAC2, critical for actin cytoskeleton remodeling and intracellular signal transduction, are associated with neonatal severe combined immunodeficiency (SCID), infantile neutrophilic disorder resembling leukocyte adhesion deficiency (LAD), and later-onset combined immune deficiency (CID). We investigated 54 patients (23 previously reported) from 37 families yielding 15 novel RAC2 missense mutations, including one present only in homozygosity. Data were collected from referring physicians and literature reports with updated clinical information. Patients were grouped by presentation: neonatal SCID (n = 5), infantile LAD-like disease (n = 5), or CID (n = 44). Disease correlated to RAC2 activity: constitutively active RAS-like mutations caused neonatal SCID, dominant-negative mutations caused LAD-like disease, whereas dominant-activating mutations caused CID. Significant T- and B-lymphopenia with low immunoglobulins were seen in most patients; myeloid abnormalities included neutropenia, altered oxidative burst, impaired neutrophil migration, and visible neutrophil macropinosomes. Among 42 patients with CID with clinical data, upper and lower respiratory infections and viral infections were common. Twenty-three distinct RAC2 mutations, including 15 novel variants, were identified. Using heterologous expression systems, we assessed downstream effector functions including superoxide production, p21-activated kinase 1 binding, AKT activation, and protein stability. Confocal microscopy showed altered actin assembly evidenced by membrane ruffling and macropinosomes. Altered protein localization and aggregation were observed. All tested RAC2 mutant proteins exhibited aberrant function; no single assay was sufficient to determine functional consequence. Most mutants produced elevated superoxide; mutations unable to support superoxide formation were associated with bacterial infections. RAC2 mutations cause a spectrum of immune dysfunction, ranging from early onset SCID to later-onset combined immunodeficiencies depending on RAC2 activity. This trial was registered at www.clinicaltrials.gov as #NCT00001355 and #NCT00001467.
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Affiliation(s)
- Ágnes Donkó
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Svetlana O. Sharapova
- Research Department, Belarusian Research Center for Pediatric Oncology, Hematology and Immunology, Minsk, Belarus
| | - Juraj Kabat
- Research Technologies Branch, Biological Imaging Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Sundar Ganesan
- Research Technologies Branch, Biological Imaging Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Fabian H. Hauck
- Department of Pediatrics, Dr. von Hauner Children's Hospital, University Hospital, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jenna R. E. Bergerson
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Louis Marois
- Department of Medicine, Centre Hospitalier Universitaire de Montréal and Institut de Recherches Cliniques de Montréal, Université de Montréal, Montreal, QC, Canada
- Department of Medecine, Centre Hospitalier Universitaire de Québec, Université de Laval, Québec, QC, Canada
| | - Jordan Abbott
- University of Colorado School of Medicine, Department of Pediatrics, Section of Allergy and Immunology, Children’s Hospital of Colorado, Aurora, CO
| | - Despina Moshous
- Pediatric Hematology-Immunology and Rheumatology Department, Hôpital Necker-Enfants Malades, Assistance Publique – Hôpitaux de Paris Centre Université de Paris, Paris, France
- Université de Paris, Imagine Institute, Laboratory of Genome Dynamics in the Immune System, INSERM UMR 1163, Paris, France
| | - Kelli W. Williams
- Department of Pediatrics, Medical University of South Carolina, Charleston, SC
| | | | - Paul L. Martin
- Division of Transplant and Cellular Therapy, Duke University Medical School, Durham, NC
| | - Chantal Lagresle-Peyrou
- Université Paris Cité, Imagine Institute, INSERM UMR 1163, Paris, France
- Biotherapy Clinical Investigation Center, Groupe Hospitalier Universitaire Ouest, Assistance Publique–Hôpitaux de Paris, INSERM, Paris, France
| | | | - Natalia B. Kuzmenko
- D. Rogachev National Medical and Research Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Ekaterina A. Deordieva
- D. Rogachev National Medical and Research Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Elena V. Raykina
- D. Rogachev National Medical and Research Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Michael S. Abers
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Hassan Abolhassani
- Division of Clinical Immunology, Department of Laboratory Medicine, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
- Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Vincent Barlogis
- Pediatric Hematology Unit, La Timone University Hospital, Marseille, France
| | - Carlos Milla
- Center for Excellence in Pulmonary Biology, Stanford University School of Medicine, Stanford, CA
| | - Geoffrey Hall
- Department of Pediatrics, Division of Pediatric Allergy and Immunology, Duke University Medical Center, Durham, NC
| | - Talal Mousallem
- Department of Pediatrics, Division of Allergy and Immunology, Duke University Medical Center, Durham, NC
| | - Joseph Church
- Pediatric Allergy/Immunology, Children’s Hospital Los Angeles, Los Angeles, CA
- Clinical Pediatrics, Keck School of Medicine of the University of Southern California, Los Angeles, CA
| | - Neena Kapoor
- Division of Hematology, Oncology and Blood and Marrow Transplant, Children’s Hospital Los Angeles, Los Angeles, CA
| | - Guilhem Cros
- Department of Medicine, Université de Montreal, Montreal, QC, Canada
- Institut de Recherches Cliniques de Montréal, Montreal, QC, Canada
| | - Hugo Chapdelaine
- Department of Medicine, Université de Montreal, Montreal, QC, Canada
- Institut de Recherches Cliniques de Montréal, Montreal, QC, Canada
| | - Clara Franco-Jarava
- Department of Immunology, Hospital Universitari Vall d’Hebron, Barcelona, Spain
| | - Ingrid Lopez-Lerma
- Department of Immunology, Hospital Universitari Vall d’Hebron, Barcelona, Spain
| | - Maurizio Miano
- Haematology Unit, Scientific Institute for Research, Hospitalization and Healthcare Istituto Giannina Gaslini, Genoa, Italy
| | - Jennifer W. Leiding
- Division of Allergy and Immunology, Department of Pediatrics, Johns Hopkins University, Baltimore, MD
- Institute for Clinical and Translational Research, Johns Hopkins All Children’s Hospital, St. Petersburg, FL
| | - Christoph Klein
- Department of Pediatrics, Dr. von Hauner Children’s Hospital, Ludwig Maximilian University Munich, Munich, Germany
| | - Marie José Stasia
- Centre Hospitalier Universitaire Grenoble Alpes, Pôle de Biologie, Centre Diagnostic et Recherche sur la Granulomatose Septique Chronique, Grenoble, France
- Université Grenoble Alpes, Centre National de le Recherche Scientifique, CEA, UMR5075, Institut de Biologie Structurale, Grenoble, France
| | - Alain Fischer
- Université Paris Cité, Imagine Institute, Laboratory of Human Lymphohematopoiesis, INSERM UMR 1163, Paris, France
| | - Kuang-Chih Hsiao
- Department of Immunology, Starship Child Health, Te Whatu Ora, Auckland, New Zealand
- Department of Paediatrics: Child and Youth Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Timi Martelius
- Inflammation Center/Infectious Diseases, University of Helsinki and HUS Helsinki University Hospital, Helsinki, Finland
| | - Mikko R. J. Sepännen
- Adult Immunodeficiency Unit, Infectious Diseases, Inflammation Center, University of Helsinki and HUS Helsinki University Hospital, Helsinki, Finland
- ERN-RITA Core Center Member, RITAFIN, Helsinki, Finland
- Rare Disease Center and Pediatric Research Center, Children and Adolescents, University of Helsinki and HUS Helsinki University Hospital, Helsinki, Finland
- Translational Immunology Research Program, University of Helsinki, Helsinki, Finland
| | - Sara Barmettler
- Division of Rheumatology, Allergy and Immunology, Massachusetts General Hospital, Boston, MA
| | - Jolan Walter
- University of South Florida at Johns Hopkins All Children’s Hospital, St. Petersburg, FL
| | - Tania N. Masmas
- Pediatric Hematopoietic Stem Cell Transplantation and Immunodeficiency, The Child and Adolescent Department, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Anna A. Mukhina
- D. Rogachev National Medical and Research Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Emilia Liana Falcone
- Center for Inflammation, Immunity and Infectious Diseases, Montreal Clinical Research Institute, Montreal, QC, Canada
- Department of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Microbiology, Infectious Diseases and Immunology, Université de Montréal, Montreal, QC, Canada
| | - Sven Kracker
- Université Paris Cité, Imagine Institute, Laboratory of Human Lymphohematopoiesis, INSERM UMR 1163, Paris, France
| | - Anna Shcherbina
- D. Rogachev National Medical and Research Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russia
| | - Steven M. Holland
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Thomas L. Leto
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Amy P. Hsu
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
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Hall G, Donkó Á, Pratt C, Kim-Chang JJ, Martin PL, Stallings AP, Sleasman JW, Holland SM, Hsu AP, Leto TL, Mousallem T. Case Report: Profound newborn leukopenia related to a novel RAC2 variant. Front Pediatr 2024; 12:1365187. [PMID: 38516355 PMCID: PMC10954883 DOI: 10.3389/fped.2024.1365187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 02/19/2024] [Indexed: 03/23/2024] Open
Abstract
We report the case of a 1-week-old male born full-term, who had two inconclusive severe combined immunodeficiency (SCID) newborn screens and developed scalp cellulitis and Escherichia coli bacteremia. He did not pass early confirmatory hearing screens. Initial blood counts and lymphocyte flow cytometry revealed profound neutropenia and lymphopenia with a T-/B-/NK- phenotype. Red blood cell adenosine deaminase 1 activity was within normal limits. A presumptive diagnosis of reticular dysgenesis was considered. Granulocyte colony-stimulating factor was started, but there was no improvement in neutrophil counts. Subsequent lymphocyte flow cytometry at around 4 weeks of age demonstrated an increase in T-, B- and NK-cell numbers, eliminating suspicion for SCID and raising concern for congenital neutropenia and bone marrow failure syndromes. Genetic testing revealed a novel variant in RAC2 [c.181C>A (p.Gln61Lys)] (Q61K). RAC2, a Ras-related GTPase, is the dominant RAC protein expressed in hematopoietic cells and is involved with various downstream immune-mediated responses. Pathogenic RAC2 variants show significant phenotypic heterogeneity (spanning from neutrophil defects to combined immunodeficiency) across dominant, constitutively activating, dominant activating, dominant negative, and autosomal recessive subtypes. Given the identification of a novel variant, functional testing was pursued to evaluate aberrant pathways described in other RAC2 pathogenic variants. In comparison to wild-type RAC2, the Q61K variant supported elevated superoxide production under both basal and PMA-stimulated conditions, increased PAK1 binding, and enhanced plasma membrane ruffling, consistent with other dominant, constitutively active mutations. This case highlights the diagnostic challenge associated with genetic variants identified via next-generation sequencing panels and the importance of functional assays to confirm variant pathogenicity.
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Affiliation(s)
- Geoffrey Hall
- Division of Allergy and Immunology, Department of Pediatrics, Duke University, Durham, NC, United States
| | - Ágnes Donkó
- Molecular Defenses Section, Laboratory of Clinical Immunology and Microbiology (LCIM), National Institute of Allergy and Infectious Disease (NIAID), National Institutes of Health (NIH), Bethesda, MD, United States
| | - Cristina Pratt
- Division of Allergy and Immunology, Department of Pediatrics, Duke University, Durham, NC, United States
| | - Julie J. Kim-Chang
- Division of Allergy and Immunology, Department of Pediatrics, Duke University, Durham, NC, United States
| | - Paul L. Martin
- Division of Pediatric Transplant and Cellular Therapy, Department of Pediatrics, Duke University, Durham, NC, United States
| | - Amy P. Stallings
- Division of Allergy and Immunology, Department of Pediatrics, Duke University, Durham, NC, United States
| | - John W. Sleasman
- Division of Allergy and Immunology, Department of Pediatrics, Duke University, Durham, NC, United States
| | - Steven M. Holland
- Immunopathogenesis Section, Laboratory of Clinical Immunology and Microbiology (LCIM), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD, United States
| | - Amy P. Hsu
- Immunopathogenesis Section, Laboratory of Clinical Immunology and Microbiology (LCIM), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD, United States
| | - Thomas L. Leto
- Molecular Defenses Section, Laboratory of Clinical Immunology and Microbiology (LCIM), National Institute of Allergy and Infectious Disease (NIAID), National Institutes of Health (NIH), Bethesda, MD, United States
| | - Talal Mousallem
- Division of Allergy and Immunology, Department of Pediatrics, Duke University, Durham, NC, United States
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Ashby L, Chan L, Winterbourn C, Woon ST, Keating P, Heller R, Ameratunga R, Chua I, Hsiao KC. Phenotypic spectrum in a family with a novel RAC2 p.I21S dominant-activating mutation. Clin Transl Immunology 2024; 13:e1493. [PMID: 38410820 PMCID: PMC10895683 DOI: 10.1002/cti2.1493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 02/11/2024] [Accepted: 02/12/2024] [Indexed: 02/28/2024] Open
Abstract
Objectives Dominant-activating (DA) lesions in RAC2 have been reported in 18 individuals to date. Some have required haematopoietic stem cell transplantation (HSCT) for their (severe) combined immunodeficiency syndrome phenotype. We aimed to investigate clinical and cellular features of a kindred harbouring a novel variant in RAC2 p.Ile21Ser (I21S) to better understand DA lesions' phenotypic spectrum. Methods Clinical and immunological information was collated for seven living individuals from the same kindred with RAC2 p.I21S. We evaluated neutrophil morphology, RAC2 protein expression and superoxide production using freshly isolated neutrophils stimulated with phorbol-12-myristate-13-acetate (PMA) and N-formyl-MetLeuPhe (fMLP). Results Patient 1 (P1, aged 11, male) has a history of bacterial suppurative otitis media, viral and bacterial cutaneous infections. P1's siblings (P2, P3), mother (P4), maternal aunt (P5) and uncle (P6) have similar infection histories. P1's maternal cousin (P7) presented with Burkitt's lymphoma at age 9. All affected individuals are alive and none has required HSCT to date. They have chronic lymphopenia affecting the CD4+T and B-cell compartments. P1-3 have isolated reduction in IgM levels whereas the adults universally have normal immunoglobulins. Specific antibody responses are preserved. Affected individuals have neutrophil vacuolation, and their neutrophils have enhanced superoxide production compared to healthy controls. Conclusion RAC2 p.I21S is an activating variant causing notable morphological and functional abnormalities similar to other reported DA mutations. This novel variant expands the broad clinical phenotypic spectrum of RAC2 DA lesions, emphasising the need to tailor clinical management according to patients' disease phenotype and severity.
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Affiliation(s)
- Louisa Ashby
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science University of Otago Christchurch Christchurch New Zealand
| | - Lydia Chan
- Department of Clinical Immunology Auckland City Hospital Auckland New Zealand
| | - Christine Winterbourn
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science University of Otago Christchurch Christchurch New Zealand
| | - See-Tarn Woon
- LabPLUS Te Toka Tumai, Te Whatu Ora Auckland New Zealand
| | - Paula Keating
- Canterbury Health Laboratories Te Whatu Ora Christchurch New Zealand
| | - Raoul Heller
- Genetic Health Service NZ - Northern Hub, Te Toka Tumai Auckland New Zealand
| | - Rohan Ameratunga
- Department of Clinical Immunology Auckland City Hospital Auckland New Zealand
- LabPLUS Te Toka Tumai, Te Whatu Ora Auckland New Zealand
| | - Ignatius Chua
- Canterbury Health Laboratories Te Whatu Ora Christchurch New Zealand
- Christchurch Hospital Te Whatu Ora Christchurch New Zealand
| | - Kuang-Chih Hsiao
- Starship Child Health Te Whatu Ora Auckland New Zealand
- Department of Paediatrics: Child and Youth Health, Faculty of Medical and Health Sciences University of Auckland Auckland New Zealand
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Ameratunga R, Edwards ESJ, Lehnert K, Leung E, Woon ST, Lea E, Allan C, Chan L, Steele R, Longhurst H, Bryant VL. The Rapidly Expanding Genetic Spectrum of Common Variable Immunodeficiency-Like Disorders. THE JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY. IN PRACTICE 2023; 11:1646-1664. [PMID: 36796510 DOI: 10.1016/j.jaip.2023.01.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/21/2023] [Accepted: 01/27/2023] [Indexed: 02/16/2023]
Abstract
The understanding of common variable immunodeficiency disorders (CVID) is in evolution. CVID was previously a diagnosis of exclusion. New diagnostic criteria have allowed the disorder to be identified with greater precision. With the advent of next-generation sequencing (NGS), it has become apparent that an increasing number of patients with a CVID phenotype have a causative genetic variant. If a pathogenic variant is identified, these patients are removed from the overarching diagnosis of CVID and are deemed to have a CVID-like disorder. In populations where consanguinity is more prevalent, the majority of patients with severe primary hypogammaglobulinemia will have an underlying inborn error of immunity, usually an early-onset autosomal recessive disorder. In nonconsanguineous societies, pathogenic variants are identified in approximately 20% to 30% of patients. These are often autosomal dominant mutations with variable penetrance and expressivity. To add to the complexity of CVID and CVID-like disorders, some genetic variants such as those in TNFSF13B (transmembrane activator calcium modulator cyclophilin ligand interactor) predispose to, or enhance, disease severity. These variants are not causative but can have epistatic (synergistic) interactions with more deleterious mutations to worsen disease severity. This review is a description of the current understanding of genes associated with CVID and CVID-like disorders. This information will assist clinicians in interpreting NGS reports when investigating the genetic basis of disease in patients with a CVID phenotype.
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Affiliation(s)
- Rohan Ameratunga
- Department of Clinical immunology, Auckland Hospital, Auckland, New Zealand; Department of Virology and Immunology, Auckland Hospital, Auckland, New Zealand; Department of Molecular Medicine and Pathology, School of Medicine, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
| | - Emily S J Edwards
- The Jeffrey Modell Diagnostic and Research Centre for Primary Immunodeficiencies, and Allergy and Clinical Immunology Laboratory, Department of Immunology, Monash University, Melbourne, VIC, Australia
| | - Klaus Lehnert
- Applied Translational Genetics Group, School of Biological Sciences, University of Auckland, Auckland, New Zealand; Maurice Wilkins Centre, School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Euphemia Leung
- Auckland Cancer Society Research Centre, School of Medicine, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - See-Tarn Woon
- Department of Virology and Immunology, Auckland Hospital, Auckland, New Zealand
| | - Edward Lea
- Department of Virology and Immunology, Auckland Hospital, Auckland, New Zealand
| | - Caroline Allan
- Department of Virology and Immunology, Auckland Hospital, Auckland, New Zealand
| | - Lydia Chan
- Department of Clinical immunology, Auckland Hospital, Auckland, New Zealand
| | - Richard Steele
- Department of Virology and Immunology, Auckland Hospital, Auckland, New Zealand; Department of Respiratory Medicine, Wellington Hospital, Wellington, New Zealand
| | - Hilary Longhurst
- Department of Medicine, School of Medicine, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Vanessa L Bryant
- Department of Immunology, Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia; Department of Clinical Immunology and Allergy, Royal Melbourne Hospital, Parkville, VIC, Australia
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Hsu AP. Not too little, not too much: the impact of mutation types in Wiskott-Aldrich syndrome and RAC2 patients. Clin Exp Immunol 2023; 212:137-146. [PMID: 36617178 PMCID: PMC10128166 DOI: 10.1093/cei/uxad001] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 11/23/2022] [Accepted: 01/04/2023] [Indexed: 01/09/2023] Open
Abstract
Primary immune deficiencies (PIDs) are genetic disorders impacting the appropriate development or functioning of any portion of the immune system. The broad adoption of high-throughput sequencing has driven discovery of new genes as well as expanded phenotypes associated with known genes. Beginning with the identification of WAS mutations in patients with severe Wiskott-Aldrich Syndrome, recognition of WAS mutations in additional patients has revealed phenotypes including isolated thrombocytopenia and X-linked neutropenia. Likewise RAC2 patients present with vastly different phenotypes depending on the mutation-ranging from reticular dysgenesis or severe neutrophil dysfunction with neonatal presentation to later onset common variable immune deficiency. This review examines genotype-phenotype correlations in patients with WAS (Wiskott-Aldrich Syndrome) and RAC2 mutations, highlighting functional protein domains, how mutations alter protein interactions, and how specific mutations can affect isolated functions of the protein leading to disparate phenotypes.
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Affiliation(s)
- Amy P Hsu
- Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
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Duan X, Shen F, Deng Y, Zhang J, Fang F, Luo Z, Chen Y, Yang Y. Novel Loss of Function (G15D) Mutation on RAC2 in a Family with Combined Immunodeficiency and Increased Levels of Immunoglobulin G, A, and E. J Clin Immunol 2023; 43:604-614. [PMID: 36459342 DOI: 10.1007/s10875-022-01411-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 11/20/2022] [Indexed: 12/04/2022]
Abstract
Ras-related C3 botulinum toxin substrate 2 (RAC2) is a small guanine nucleotide binding molecule that is exclusively expressed in hematopoietic cell lineages as a switcher. Based on in vivo and/or in vitro model experiments, RAC2 plays important roles in different cells through proliferation, secretion, and phagocytosis. It also performs a suppressing function in immunoglobulin (Ig) switching in Rac2-/- animals or cells. Several RAC2 natural mutations have been described in patients with primary immunodeficiency. RAC2 mutations can be classified into loss-of-function inactivating (LoF-I) and gain-of-function activating mutations according to their functional effects. Only two LoF-I mutations on RAC2 have been reported, including a dominant D57N mutation in several cases that exhibit granulocyte function defects and a recessive D56X mutation in cases with common variable immunodeficiency. Regardless of the type of mutation, most of the reported RAC2 mutant cases have shown reduced IgG, IgA, and IgM levels. Herein, we report on a family with three members that suffer from persistent HPV infection, recurrent respiratory infections, bronchiectasis, and autoimmune disease. The immunologic profile suggests that the family was affected by combined immunodeficiency (CID) with increased serum levels of IgG, IgA, and IgE. Exome sequencing identified a de novo RAC2 mutation (c.44G > A/p.G15D) that was co-segregated with the disease in the family. Gene functional experiments identified that such mutation results in reduced guanosine triphosphate binding activity and RAC2 protein expression. In patients' lymphocytes, impaired aggregation and proliferation effects, decreased mitochondrial membrane potential, and increased levels of cell apoptosis were observed, although no functional abnormalities were detected in neutrophils. To our knowledge, this study was the first to identify a LoF-I mutation of RAC2 affecting lymphocyte function that consequently led to CID and increased levels of serum IgG, IgE, and IgA. This study presents a novel subtype of RAC2-related immune disorder.
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Affiliation(s)
- Xiaojun Duan
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China
| | - Fang Shen
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China
| | - Yafei Deng
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China
| | - Jin Zhang
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China
| | - Fan Fang
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China
| | - Zhenqing Luo
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China
| | - Yanping Chen
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China.
| | - Yongjia Yang
- Hunan Children's Hospital & School of Pediatrics, Hengyang Medical School, University of South China, Hunan, 421001, China.
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7
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Zhang L, Lv G, Peng Y, Yang L, Chen J, An Y, Zhang Z, Tang X, Li Z, Zhao X. A Novel RAC2 Mutation Causing Combined Immunodeficiency. J Clin Immunol 2023; 43:229-240. [PMID: 36190591 DOI: 10.1007/s10875-022-01373-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 09/24/2022] [Indexed: 01/18/2023]
Abstract
PURPOSE Ras-related C3 botulinum toxin substrate 2 (RAC2) acts as a molecular switch and has crucial roles in cell signaling and actin dynamics. A broad spectrum of genetic RAC2 mutations can cause various types of primary immunodeficiency, with complete penetrance. Here, we report a novel heterozygous missense mutation in RAC2 with incomplete penetrance, and the associated phenotypes, in a Chinese family. METHODS Immunological phenotype was detected by flow cytometry. T cell receptor excision circles (TRECs) and K-deleting recombination excision circles (KRECs) were assessed by real-time quantitative PCR. Gene mutations were detected by whole-exome sequencing (WES) and confirmed by Sanger sequencing. RESULTS The proband was an 11-year-old girl who presented with recurrent respiratory infections, bronchiectasis, persistent Epstein-Barr virus viremia, infectious mononucleosis, encephalitis, and cutaneous human papillomavirus infections. Laboratory analyses revealed increased serum IgG and decreased IgM levels, reduced naïve CD4+ and CD8+ T cells, an inverted CD4+/CD8+ ratio, and low TREC and KREC numbers. The mutation resulted in increased production of reactive oxygen species, while impaired actin polarization in neutrophils; diminished proliferative responses, increased cytokine production and a dysregulated phenotype in T lymphocytes; as well as accelerated apoptosis and hyperactivity of AKT in HL-60 human leukemia cells. WES identified a c.44G > A mutation in RAC2 resulting in a p.G15D substitution. Despite sharing the same mutation as the proband, her father suffered from recurrent respiratory infections and bronchiectasis, and had similar immunological defects, whereas her sister was apparently healthy, other than cutaneous human papillomavirus infections, and only mild immunological defects were detected preliminarily. CONCLUSIONS Our findings broaden the clinical and genetic spectra of RAC2 mutations and underline the importance of RAC2 gain-of-function mutations with complete or incomplete penetrance.
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Affiliation(s)
- Liang Zhang
- Department of Nephrology, Rheumatology and Immunology, Hunan Children's Hospital, Changsha, Hunan, China
- The School of Pediatrics, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Ge Lv
- Department of Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders (Chongqing), China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, China
- Division of Rheumatology and Immunology, Children's Hospital of Chongqing Medical University, Chongqing, China
| | - Yu Peng
- The School of Pediatrics, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Department of Pediatrics Research Institute, Hunan Children's Hospital, Changsha, Hunan, China
| | - Lu Yang
- Department of Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders (Chongqing), China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, China
- Division of Rheumatology and Immunology, Children's Hospital of Chongqing Medical University, Chongqing, China
| | - Junjie Chen
- Department of Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders (Chongqing), China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, China
- Division of Rheumatology and Immunology, Children's Hospital of Chongqing Medical University, Chongqing, China
| | - Yunfei An
- Department of Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders (Chongqing), China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, China
- Division of Rheumatology and Immunology, Children's Hospital of Chongqing Medical University, Chongqing, China
| | - Zhiyong Zhang
- Department of Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders (Chongqing), China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, China
- Division of Rheumatology and Immunology, Children's Hospital of Chongqing Medical University, Chongqing, China
| | - Xuemei Tang
- Department of Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders (Chongqing), China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, China
- Division of Rheumatology and Immunology, Children's Hospital of Chongqing Medical University, Chongqing, China
| | - Zhihui Li
- Department of Nephrology, Rheumatology and Immunology, Hunan Children's Hospital, Changsha, Hunan, China.
- The School of Pediatrics, Hengyang Medical School, University of South China, Hengyang, Hunan, China.
| | - Xiaodong Zhao
- Department of Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders (Chongqing), China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China.
- Chongqing Key Laboratory of Child Infection and Immunity, Children's Hospital of Chongqing Medical University, Chongqing, China.
- Division of Rheumatology and Immunology, Children's Hospital of Chongqing Medical University, Chongqing, China.
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