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Marques I, Sá MJ, Soares G, Mota MDC, Pinheiro C, Aguiar L, Amado M, Soares C, Calado A, Dias P, Sousa AB, Fortuna AM, Santos R, Howell KB, Ryan MM, Leventer RJ, Sachdev R, Catford R, Friend K, Mattiske TR, Shoubridge C, Jorge P. Unraveling the pathogenesis of ARX polyalanine tract variants using a clinical and molecular interfacing approach. Mol Genet Genomic Med 2015; 3:203-14. [PMID: 26029707 PMCID: PMC4444162 DOI: 10.1002/mgg3.133] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 01/13/2015] [Accepted: 01/15/2015] [Indexed: 12/22/2022] Open
Abstract
The Aristaless-related homeobox (ARX) gene is implicated in intellectual disability with the most frequent pathogenic mutations leading to expansions of the first two polyalanine tracts. Here, we describe analysis of the ARX gene outlining the approaches in the Australian and Portuguese setting, using an integrated clinical and molecular strategy. We report variants in the ARX gene detected in 19 patients belonging to 17 families. Seven pathogenic variants, being expansion mutations in both polyalanine tract 1 and tract 2, were identifyed, including a novel mutation in polyalanine tract 1 that expands the first tract to 20 alanines. This precise number of alanines is sufficient to cause pathogenicity when expanded in polyalanine tract 2. Five cases presented a probably non-pathogenic variant, including the novel HGVS: c.441_455del, classified as unlikely disease causing, consistent with reports that suggest that in frame deletions in polyalanine stretches of ARX rarely cause intellectual disability. In addition, we identified five cases with a variant of unclear pathogenic significance. Owing to the inconsistent ARX variants description, publications were reviewed and ARX variant classifications were standardized and detailed unambiguously according to recommendations of the Human Genome Variation Society. In the absence of a pathognomonic clinical feature, we propose that molecular analysis of the ARX gene should be included in routine diagnostic practice in individuals with either nonsyndromic or syndromic intellectual disability. A definitive diagnosis of ARX-related disorders is crucial for an adequate clinical follow-up and accurate genetic counseling of at-risk family members.
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Affiliation(s)
- Isabel Marques
- Unidade de Genética Molecular, Centro de Genética Médica Doutor Jacinto Magalhães, Centro Hospitalar do Porto, EPE Porto, Portugal ; Unit for Multidisciplinary Research in Biomedicine, UMIB, ICBAS-UP Porto, Portugal
| | - Maria João Sá
- Unidade de Genética Médica, Centro de Genética Médica Doutor Jacinto Magalhães, Centro Hospitalar do Porto, EPE Porto, Portugal ; Unit for Multidisciplinary Research in Biomedicine, UMIB, ICBAS-UP Porto, Portugal
| | - Gabriela Soares
- Unidade de Genética Médica, Centro de Genética Médica Doutor Jacinto Magalhães, Centro Hospitalar do Porto, EPE Porto, Portugal
| | - Maria do Céu Mota
- Department of Pediatrics, Centro Hospitalar do Porto, EPE Porto, Portugal
| | - Carla Pinheiro
- Department of Pediatrics, Hospital Santa Maria Maior, EPE Barcelos, Portugal
| | - Lisa Aguiar
- Department of Pediatrics, Hospital Distrital de Santarém, EPE Santarém, Portugal
| | - Marta Amado
- Department of Pediatrics, Unidade Hospitalar de Portimão, Centro Hospitalar do Algarve Portimão, Portugal
| | - Christina Soares
- Department of Pediatrics, Unidade Hospitalar de Portimão, Centro Hospitalar do Algarve Portimão, Portugal
| | - Angelina Calado
- Department of Pediatrics, Unidade Hospitalar de Portimão, Centro Hospitalar do Algarve Portimão, Portugal
| | - Patrícia Dias
- Department of Genetics, Hospital de Santa Maria Lisboa, Portugal
| | - Ana Berta Sousa
- Department of Genetics, Hospital de Santa Maria Lisboa, Portugal
| | - Ana Maria Fortuna
- Unidade de Genética Médica, Centro de Genética Médica Doutor Jacinto Magalhães, Centro Hospitalar do Porto, EPE Porto, Portugal ; Unit for Multidisciplinary Research in Biomedicine, UMIB, ICBAS-UP Porto, Portugal
| | - Rosário Santos
- Unidade de Genética Molecular, Centro de Genética Médica Doutor Jacinto Magalhães, Centro Hospitalar do Porto, EPE Porto, Portugal ; Unit for Multidisciplinary Research in Biomedicine, UMIB, ICBAS-UP Porto, Portugal
| | - Katherine B Howell
- Department of Neurology, Royal Children's Hospital Melbourne, Victoria, Australia ; Murdoch Childrens Research Institute Melbourne, Victoria, Australia, 3052 ; University of Melbourne Department of Paediatrics Melbourne, Victoria, Australia, 3052
| | - Monique M Ryan
- Department of Neurology, Royal Children's Hospital Melbourne, Victoria, Australia ; Murdoch Childrens Research Institute Melbourne, Victoria, Australia, 3052 ; University of Melbourne Department of Paediatrics Melbourne, Victoria, Australia, 3052
| | - Richard J Leventer
- Department of Neurology, Royal Children's Hospital Melbourne, Victoria, Australia ; Murdoch Childrens Research Institute Melbourne, Victoria, Australia, 3052 ; University of Melbourne Department of Paediatrics Melbourne, Victoria, Australia, 3052
| | - Rani Sachdev
- Department of Medical Genetics, Sydney Children's Hospital High St., Randwick, New South Wales, 2031, Australia
| | - Rachael Catford
- SA Pathology at the Women's and Children's Hospital North Adelaide, South Australia, Australia
| | - Kathryn Friend
- SA Pathology at the Women's and Children's Hospital North Adelaide, South Australia, Australia
| | - Tessa R Mattiske
- Department of Paediatrics, University of Adelaide Adelaide, South Australia, 5006, Australia ; Robinson Research Institute, University of Adelaide Adelaide, South Australia, 5006, Australia
| | - Cheryl Shoubridge
- Department of Paediatrics, University of Adelaide Adelaide, South Australia, 5006, Australia ; Robinson Research Institute, University of Adelaide Adelaide, South Australia, 5006, Australia
| | - Paula Jorge
- Unidade de Genética Molecular, Centro de Genética Médica Doutor Jacinto Magalhães, Centro Hospitalar do Porto, EPE Porto, Portugal ; Unit for Multidisciplinary Research in Biomedicine, UMIB, ICBAS-UP Porto, Portugal
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