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Rao NT, Sumaroka A, Santos AJ, Parchinski KM, Weber ML, Maguire AM, Cideciyan AV, Aleman TS. Detailed phenotype and long-term follow-up of RAB28-associated cone-rod dystrophy. Ophthalmic Genet 2024:1-10. [PMID: 38956823 DOI: 10.1080/13816810.2024.2362204] [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: 02/14/2024] [Accepted: 05/27/2024] [Indexed: 07/04/2024]
Abstract
PURPOSE To gain an insight into the pathophysiology of RAB28-associated inherited retinal degeneration through detailed phenotyping and long-term longitudinal follow-up. METHODS The patient underwent complete ophthalmic examinations. Visual function was assessed with microperimetry, full-field electroretinography (ffERG), imaging with optical coherence tomography (OCT), short-wave (SW), and near-infrared (NIR) fundus autofluorescence (FAF). RESULTS A healthy Haitian woman with homozygous pathogenic variants (c.68C > T; p.Ser23Phe) in RAB28 presented at 16 years of age with a four-year history of blurred vision. Visual acuities were 20/125 in each eye, which remained relatively stable since. At age 27, cone ffERGs were non-detectable and borderline for rod-mediated responses. Kinetic fields were full to a V-4e target, undetectable to a small I-4e stimulus. Microperimetry showed an absolute central scotoma surrounded by a pericentral relative scotoma. SD-OCT showed an undetectable or barely detectable foveal and parafoveal photoreceptor outer nuclear layer (ONL), photoreceptor outer segment (POS), and retinal pigment epithelium (RPE) signals and loss of the SW- and NIR-FAF signals. This atrophic region was separated from a normally laminated retina by a narrow transition zone (TZ) of hyper SW- and NIR-FAF that co-localized with preserved ONL but abnormally thinned POS and RPE. There was minimal centrifugal (<100 μ m) expansion over a six-year period. CONCLUSION The cone-rod dystrophy phenotype documented herein supports a critical role of RAB28 for cone function and POS maintenance. Severe central photoreceptor and RPE loss with a predilection for POS loss in TZs suggests possible disruptions of complex mechanisms that maintain central cone photoreceptor and RPE homeostasis.
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Affiliation(s)
- Nitya T Rao
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Alexander Sumaroka
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Arlene J Santos
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Kelsey M Parchinski
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Mariejel L Weber
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Albert M Maguire
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Division of Ophthalmology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Artur V Cideciyan
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Tomas S Aleman
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Division of Ophthalmology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
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2
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Xie S, Xie X, Tang J, Luo B, Chen J, Wen Q, Zhou J, Chen G. Cerebral furin deficiency causes hydrocephalus in mice. Genes Dis 2024; 11:101009. [PMID: 38292192 PMCID: PMC10825277 DOI: 10.1016/j.gendis.2023.04.037] [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: 12/13/2022] [Revised: 04/20/2023] [Accepted: 04/29/2023] [Indexed: 02/01/2024] Open
Abstract
Furin is a pro-protein convertase that moves between the trans-Golgi network and cell surface in the secretory pathway. We have previously reported that cerebral overexpression of furin promotes cognitive functions in mice. Here, by generating the brain-specific furin conditional knockout (cKO) mice, we investigated the role of furin in brain development. We found that furin deficiency caused early death and growth retardation. Magnetic resonance imaging showed severe hydrocephalus. In the brain of furin cKO mice, impaired ciliogenesis and the derangement of microtubule structures appeared along with the down-regulated expression of RAB28, a ciliary vesicle protein. In line with the widespread neuronal loss, ependymal cell layers were damaged. Further proteomics analysis revealed that cell adhesion molecules including astrocyte-enriched ITGB8 and BCAR1 were altered in furin cKO mice; and astrocyte overgrowth was accompanied by the reduced expression of SOX9, indicating a disrupted differentiation into ependymal cells. Together, whereas alteration of RAB28 expression correlated with the role of vesicle trafficking in ciliogenesis, dysfunctional astrocytes might be involved in ependymal damage contributing to hydrocephalus in furin cKO mice. The structural and molecular alterations provided a clue for further studying the potential mechanisms of furin.
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Affiliation(s)
- Shiqi Xie
- Nursing College, Chongqing Medical University, Chongqing 400016, China
| | - Xiaoyong Xie
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Major Neurological and Mental Disorders, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Jing Tang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Major Neurological and Mental Disorders, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Biao Luo
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Major Neurological and Mental Disorders, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Jian Chen
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Major Neurological and Mental Disorders, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Qixin Wen
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Major Neurological and Mental Disorders, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Jianrong Zhou
- Nursing College, Chongqing Medical University, Chongqing 400016, China
| | - Guojun Chen
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Major Neurological and Mental Disorders, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
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Han R, Chu M, Gao J, Wang J, Wang M, Ma Y, Jia T, Zhang X. Compound heterozygous variants of THG1L result in autosomal recessive cerebellar ataxia. J Hum Genet 2023; 68:843-848. [PMID: 37670026 DOI: 10.1038/s10038-023-01192-8] [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: 04/11/2023] [Revised: 07/04/2023] [Accepted: 08/23/2023] [Indexed: 09/07/2023]
Abstract
tRNA-histidine guanyltransferase 1-like protein (THG1L), located in the mitochondria, plays a crucial role in the tRNA maturation process. Dysfunction of THG1L results in abnormal mitochondrial tRNA modification and neurodevelopmental disorders. To date, few studies have focused on THG1L-related cerebellar ataxia. Whole-exome sequencing revealed compound heterozygous variants NM_017872.5: [c.224A > G]; [c.369-8T > G] in THG1L in a 6-year-old boy with moderate cerebellar ataxia. The variant c.224A > G was demonstrated to downregulate its RNA and protein expression, and c.369-8 T > G resulted in a 7 bp insertion before exon 3. Our case expanded the gene variation and clinical spectrum of THG1L-related cerebellar ataxia.
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Affiliation(s)
- Rui Han
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China
| | - Manman Chu
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China
| | - Jinshuang Gao
- Clinical Laboratory, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China
| | - Junling Wang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China
| | - Mengyue Wang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China
| | - Yichao Ma
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China
| | - Tianming Jia
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China
| | - Xiaoli Zhang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, 450052, Zhengzhou, Henan, China.
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4
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Moran AL, Fehilly JD, Blacque O, Kennedy BN. Gene therapy for RAB28: What can we learn from zebrafish? Vision Res 2023; 210:108270. [PMID: 37321111 DOI: 10.1016/j.visres.2023.108270] [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: 02/02/2023] [Revised: 05/12/2023] [Accepted: 05/12/2023] [Indexed: 06/17/2023]
Abstract
The eye is particularly suited to gene therapy due to its accessibility, immunoprivileged state and compartmentalised structure. Indeed, many clinical trials are underway for therapeutic gene strategies for inherited retinal degenerations (IRDs). However, as there are currently 281 genes associated with IRD, there is still a large unmet need for effective therapies for the majority of IRD-causing genes. In humans, RAB28 null and hypomorphic alleles cause autosomal recessive cone-rod dystrophy (arCORD). Previous work demonstrated that restoring wild type zebrafish Rab28 via germline transgenesis, specifically in cone photoreceptors, is sufficient to rescue the defects in outer segment phagocytosis (OSP) observed in zebrafish rab28-/- knockouts (KO). This rescue suggests that gene therapy for RAB28-associated CORD may be successful by RAB28 gene restoration to cones. It also inspired us to critically consider the scenarios in which zebrafish can provide informative preclinical data for development of gene therapies. Thus, this review focuses on RAB28 biology and disease, and delves into both the opportunities and limitations of using zebrafish as a model for both gene therapy development and as a diagnostic tool for patient variants of unknown significance (VUS).
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Affiliation(s)
- Ailis L Moran
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland; UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - John D Fehilly
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland; UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Oliver Blacque
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland; UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Breandán N Kennedy
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland; UCD Conway Institute, University College Dublin, Dublin, Ireland
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5
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Derderian C, Canales GI, Reiter JF. Seriously cilia: A tiny organelle illuminates evolution, disease, and intercellular communication. Dev Cell 2023; 58:1333-1349. [PMID: 37490910 PMCID: PMC10880727 DOI: 10.1016/j.devcel.2023.06.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 01/18/2023] [Accepted: 06/30/2023] [Indexed: 07/27/2023]
Abstract
The borders between cell and developmental biology, which have always been permeable, have largely dissolved. One manifestation is the blossoming of cilia biology, with cell and developmental approaches (increasingly complemented by human genetics, structural insights, and computational analysis) fruitfully advancing understanding of this fascinating, multifunctional organelle. The last eukaryotic common ancestor probably possessed a motile cilium, providing evolution with ample opportunity to adapt cilia to many jobs. Over the last decades, we have learned how non-motile, primary cilia play important roles in intercellular communication. Reflecting their diverse motility and signaling functions, compromised cilia cause a diverse range of diseases collectively called "ciliopathies." In this review, we highlight how cilia signal, focusing on how second messengers generated in cilia convey distinct information; how cilia are a potential source of signals to other cells; how evolution may have shaped ciliary function; and how cilia research may address thorny outstanding questions.
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Affiliation(s)
- Camille Derderian
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Gabriela I Canales
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA.
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6
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Yin G, Huang J, Petela J, Jiang H, Zhang Y, Gong S, Wu J, Liu B, Shi J, Gao Y. Targeting small GTPases: emerging grasps on previously untamable targets, pioneered by KRAS. Signal Transduct Target Ther 2023; 8:212. [PMID: 37221195 DOI: 10.1038/s41392-023-01441-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 03/28/2023] [Accepted: 04/14/2023] [Indexed: 05/25/2023] Open
Abstract
Small GTPases including Ras, Rho, Rab, Arf, and Ran are omnipresent molecular switches in regulating key cellular functions. Their dysregulation is a therapeutic target for tumors, neurodegeneration, cardiomyopathies, and infection. However, small GTPases have been historically recognized as "undruggable". Targeting KRAS, one of the most frequently mutated oncogenes, has only come into reality in the last decade due to the development of breakthrough strategies such as fragment-based screening, covalent ligands, macromolecule inhibitors, and PROTACs. Two KRASG12C covalent inhibitors have obtained accelerated approval for treating KRASG12C mutant lung cancer, and allele-specific hotspot mutations on G12D/S/R have been demonstrated as viable targets. New methods of targeting KRAS are quickly evolving, including transcription, immunogenic neoepitopes, and combinatory targeting with immunotherapy. Nevertheless, the vast majority of small GTPases and hotspot mutations remain elusive, and clinical resistance to G12C inhibitors poses new challenges. In this article, we summarize diversified biological functions, shared structural properties, and complex regulatory mechanisms of small GTPases and their relationships with human diseases. Furthermore, we review the status of drug discovery for targeting small GTPases and the most recent strategic progress focused on targeting KRAS. The discovery of new regulatory mechanisms and development of targeting approaches will together promote drug discovery for small GTPases.
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Affiliation(s)
- Guowei Yin
- The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, 518107, China.
| | - Jing Huang
- State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Sun Yat-sen University Cancer Center, Guangzhou, 510060, China
| | - Johnny Petela
- Wake Forest University School of Medicine, Winston-Salem, NC, 27101, USA
| | - Hongmei Jiang
- The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, 518107, China
| | - Yuetong Zhang
- State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Sun Yat-sen University Cancer Center, Guangzhou, 510060, China
| | - Siqi Gong
- The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, 518107, China
- School of Medicine, Sun Yat-Sen University, Shenzhen, 518107, China
| | - Jiaxin Wu
- State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Sun Yat-sen University Cancer Center, Guangzhou, 510060, China
| | - Bei Liu
- National Biomedical Imaging Center, School of Future Technology, Peking University, Beijing, 100871, China
| | - Jianyou Shi
- Department of Pharmacy, Personalized Drug Therapy Key Laboratory of Sichuan Province, Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology, Chengdu, 610072, China.
| | - Yijun Gao
- State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Sun Yat-sen University Cancer Center, Guangzhou, 510060, China.
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7
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Moran AL, Carter SP, Kaylor JJ, Jiang Z, Broekman S, Dillon ET, Gómez Sánchez A, Minhas SK, van Wijk E, Radu RA, Travis GH, Carey M, Blacque OE, Kennedy BN. Dawn and dusk peaks of outer segment phagocytosis, and visual cycle function require Rab28. FASEB J 2022; 36:e22309. [PMID: 35471581 PMCID: PMC9322422 DOI: 10.1096/fj.202101897r] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 03/14/2022] [Accepted: 03/29/2022] [Indexed: 12/12/2022]
Abstract
RAB28 is a farnesylated, ciliary G-protein. Patient variants in RAB28 are causative of autosomal recessive cone-rod dystrophy (CRD), an inherited human blindness. In rodent and zebrafish models, the absence of Rab28 results in diminished dawn, photoreceptor, outer segment phagocytosis (OSP). Here, we demonstrate that Rab28 is also required for dusk peaks of OSP, but not for basal OSP levels. This study further elucidated the molecular mechanisms by which Rab28 controls OSP and inherited blindness. Proteomic profiling identified factors whose expression in the eye or whose expression at dawn and dusk peaks of OSP is dysregulated by loss of Rab28. Notably, transgenic overexpression of Rab28, solely in zebrafish cones, rescues the OSP defect in rab28 KO fish, suggesting rab28 gene replacement in cone photoreceptors is sufficient to regulate Rab28-OSP. Rab28 loss also perturbs function of the visual cycle as retinoid levels of 11-cRAL, 11cRP, and atRP are significantly reduced in larval and adult rab28 KO retinae (p < .05). These data give further understanding on the molecular mechanisms of RAB28-associated CRD, highlighting roles of Rab28 in both peaks of OSP, in vitamin A metabolism and in retinoid recycling.
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Affiliation(s)
- Ailís L. Moran
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
| | - Stephen P. Carter
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
| | - Joanna J. Kaylor
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
| | - Zhichun Jiang
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
| | - Sanne Broekman
- Department of OtorhinolaryngologyRadboud University Medical CenterNijmegenThe Netherlands
- Donders Institute for Brain, Cognition, and BehaviorNijmegenThe Netherlands
| | | | - Alicia Gómez Sánchez
- UCD Conway InstituteUniversity College DublinDublinIreland
- Ocupharm Diagnostic Group ResearchFaculty of Optic and OptometryUniversidad Complutense de MadridMadridSpain
| | - Sajal K. Minhas
- UCD School of Mathematics & StatisticsUniversity College DublinDublinIreland
| | - Erwin van Wijk
- Department of OtorhinolaryngologyRadboud University Medical CenterNijmegenThe Netherlands
- Donders Institute for Brain, Cognition, and BehaviorNijmegenThe Netherlands
| | - Roxana A. Radu
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
| | - Gabriel H. Travis
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
- Department of Biological ChemistryUniversity of CaliforniaLos Angeles School of MedicineLos AngelesCaliforniaUSA
| | - Michelle Carey
- UCD School of Mathematics & StatisticsUniversity College DublinDublinIreland
| | - Oliver E. Blacque
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
| | - Breandán N. Kennedy
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
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Villanueva-Mendoza C, Tuson M, Apam-Garduño D, de Castro-Miró M, Tonda R, Trotta JR, Marfany G, Valero R, Cortés-González V, Gonzàlez-Duarte R. The Genetic Landscape of Inherited Retinal Diseases in a Mexican Cohort: Genes, Mutations and Phenotypes. Genes (Basel) 2021; 12:genes12111824. [PMID: 34828430 PMCID: PMC8624043 DOI: 10.3390/genes12111824] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 11/16/2021] [Accepted: 11/17/2021] [Indexed: 12/16/2022] Open
Abstract
In this work, we aimed to provide the genetic diagnosis of a large cohort of patients affected with inherited retinal dystrophies (IRDs) from Mexico. Our data add valuable information to the genetic portrait in rare ocular diseases of Mesoamerican populations, which are mostly under-represented in genetic studies. A cohort of 144 unrelated probands with a clinical diagnosis of IRD were analyzed by next-generation sequencing using target gene panels (overall including 346 genes and 65 intronic sequences). Four unsolved cases were analyzed by whole-exome sequencing (WES). The pathogenicity of new variants was assessed by in silico prediction algorithms and classified following the American College of Medical Genetics and Genomics (ACMG) guidelines. Pathogenic or likely pathogenic variants were identified in 105 probands, with a final diagnostic yield of 72.9%; 17 cases (11.8%) were partially solved. Eighteen patients were clinically reclassified after a genetic diagnostic test (17.1%). In our Mexican cohort, mutations in 48 genes were found, with ABCA4, CRB1, RPGR and USH2A as the major contributors. Notably, over 50 new putatively pathogenic variants were identified. Our data highlight cases with relevant clinical and genetic features due to mutations in the RAB28 and CWC27 genes, enrich the novel mutation repertoire and expand the IRD landscape of the Mexican population.
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Affiliation(s)
| | - Miquel Tuson
- DBGen Ocular Genomics, 08028 Barcelona, Spain; (M.T.); (M.d.C.-M.); (G.M.)
| | - David Apam-Garduño
- Asociación para Evitar la Ceguera en México, Mexico City 04030, Mexico; (C.V.-M.); (D.A.-G.)
| | | | - Raul Tonda
- CNAG-CRG, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08036 Barcelona, Spain; (R.T.); (J.R.T.)
| | - Jean Remi Trotta
- CNAG-CRG, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08036 Barcelona, Spain; (R.T.); (J.R.T.)
| | - Gemma Marfany
- DBGen Ocular Genomics, 08028 Barcelona, Spain; (M.T.); (M.d.C.-M.); (G.M.)
- Department of Genetics, Microbiology and Statistics, Faculty of Biology, University of Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red en Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, 08028 Barcelona, Spain
| | - Rebeca Valero
- DBGen Ocular Genomics, 08028 Barcelona, Spain; (M.T.); (M.d.C.-M.); (G.M.)
- Correspondence: (R.V.); (V.C.-G.); (R.G.-D.)
| | - Vianney Cortés-González
- Asociación para Evitar la Ceguera en México, Mexico City 04030, Mexico; (C.V.-M.); (D.A.-G.)
- Correspondence: (R.V.); (V.C.-G.); (R.G.-D.)
| | - Roser Gonzàlez-Duarte
- DBGen Ocular Genomics, 08028 Barcelona, Spain; (M.T.); (M.d.C.-M.); (G.M.)
- Correspondence: (R.V.); (V.C.-G.); (R.G.-D.)
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9
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Expanding the Clinical and Genetic Spectrum of RAB28-Related Cone-Rod Dystrophy: Pathogenicity of Novel Variants in Italian Families. Int J Mol Sci 2020; 22:ijms22010381. [PMID: 33396523 PMCID: PMC7795990 DOI: 10.3390/ijms22010381] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 12/28/2020] [Accepted: 12/28/2020] [Indexed: 12/11/2022] Open
Abstract
The small Ras-related GTPase Rab-28 is highly expressed in photoreceptor cells, where it possibly participates in membrane trafficking. To date, six alterations in the RAB28 gene have been associated with autosomal recessive cone-rod dystrophies. Confirmed variants include splicing variants, missense and nonsense mutations. Here, we present a thorough phenotypical and genotypical characterization of five individuals belonging to four Italian families, constituting the largest cohort of RAB28 patients reported in literature to date. All probands displayed similar clinical phenotype consisting of photophobia, decreased visual acuity, central outer retinal thinning, and impaired color vision. By sequencing the four probands, we identified: a novel homozygous splicing variant; two novel nonsense variants in homozygosis; a novel missense variant in compound heterozygous state with a previously reported nonsense variant. Exhaustive molecular dynamics simulations of the missense variant p.(Thr26Asn) in both its active and inactive states revealed an allosteric structural mechanism that impairs the binding of Mg2+, thus decreasing the affinity for GTP. The impaired GTP-GDP exchange ultimately locks Rab-28 in a GDP-bound inactive state. The loss-of-function mutation p.(Thr26Asn) was present in a compound heterozygosis with the nonsense variant p.(Arg137*), which does not cause mRNA-mediated decay, but is rather likely degraded due to its incomplete folding. The frameshift p.(Thr26Valfs4*) and nonsense p.(Leu13*) and p.(Trp107*) variants, if translated, would lack several key structural components necessary for the correct functioning of the encoded protein.
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