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Maia N, Ibarluzea N, Misra-Isrie M, Koboldt DC, Marques I, Soares G, Santos R, Marcelis CLM, Keski-Filppula R, Guitart M, Gabau Vila E, Lehman A, Hickey S, Mori M, Terhal P, Valenzuela I, Lasa-Aranzasti A, Cueto-González AM, Chhouk BH, Yeh RC, Neil JE, Abu-Libde B, Kleefstra T, Elting MW, Császár A, Kárteszi J, Bessenyei B, van Bokhoven H, Jorge P, van Hagen JM, de Brouwer APM. Missense MED12 variants in 22 males with intellectual disability: From nonspecific symptoms to complete syndromes. Am J Med Genet A 2023; 191:135-143. [PMID: 36271811 PMCID: PMC10092556 DOI: 10.1002/ajmg.a.63004] [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: 05/05/2022] [Revised: 07/26/2022] [Accepted: 08/13/2022] [Indexed: 12/14/2022]
Abstract
We describe the phenotype of 22 male patients (20 probands) carrying a hemizygous missense variant in MED12. The phenotypic spectrum is very broad ranging from nonspecific intellectual disability (ID) to the three well-known syndromes: Opitz-Kaveggia syndrome, Lujan-Fryns syndrome, or Ohdo syndrome. The identified variants were randomly distributed throughout the gene (p = 0.993, χ2 test), but mostly outside the functional domains (p = 0.004; χ2 test). Statistical analyses did not show a correlation between the MED12-related phenotypes and the locations of the variants (p = 0.295; Pearson correlation), nor the protein domain involved (p = 0.422; Pearson correlation). In conclusion, establishing a genotype-phenotype correlation in MED12-related diseases remains challenging. Therefore, we think that patients with a causative MED12 variant are currently underdiagnosed due to the broad patients' clinical presentations.
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Affiliation(s)
- Nuno Maia
- Unidade de Genética Molecular, Centro de Genética Médica Doutor Jacinto de Magalhães (CGM), Centro Hospitalar Universitário do Porto (CHUPorto); Unit for Multidisciplinary Research In Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), and ITR - Laboratory for Integrative and Translational Research in Population Health, University of Porto, Porto, Portugal
| | | | - Mala Misra-Isrie
- Department of Human Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Daniel C Koboldt
- Steve and Cindy Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, USA.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, USA
| | - Isabel Marques
- Unidade de Genética Molecular, Centro de Genética Médica Doutor Jacinto de Magalhães (CGM), Centro Hospitalar Universitário do Porto (CHUPorto); Unit for Multidisciplinary Research In Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), and ITR - Laboratory for Integrative and Translational Research in Population Health, University of Porto, Porto, Portugal
| | - Gabriela Soares
- Unidade de Genética Médica, Centro de Genética Médica Doutor Jacinto de Magalhães (CGM), Centro Hospitalar Universitário do Porto (CHUPorto), Porto, Portugal
| | - Rosário Santos
- Unidade de Genética Molecular, Centro de Genética Médica Doutor Jacinto de Magalhães (CGM), Centro Hospitalar Universitário do Porto (CHUPorto); Unit for Multidisciplinary Research In Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), and ITR - Laboratory for Integrative and Translational Research in Population Health, University of Porto, Porto, Portugal
| | - Carlo L M Marcelis
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Riikka Keski-Filppula
- Department of Clinical Genetics, Oulu University Hospital, Medical Research Center Oulu and PEDEGO Research Unit, University of Oulu, Oulu, Finland
| | - Miriam Guitart
- Paediatric Unit, ParcTaulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí, I3PTUniversitat Autònoma de Barcelona, Sabadell, Spain
| | - Elisabeth Gabau Vila
- Paediatric Unit, ParcTaulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí, I3PTUniversitat Autònoma de Barcelona, Sabadell, Spain
| | - April Lehman
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, USA.,Division of Genetic & Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Scott Hickey
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio, USA.,Division of Genetic & Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Mari Mori
- Division of Genetic & Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio, USA.,Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Paulien Terhal
- Division Laboratories, Pharmacy and Biomedical Genetics, Wilhelmina Children's Hospital, Utrecht, The Netherlands
| | - Irene Valenzuela
- Department of Clinical and Molecular Genetics, Vall d'Hebron University Hospital and Medicine Genetics Group, Vall d'Hebron Research Institute, Barcelona, Spain
| | - Amaia Lasa-Aranzasti
- Department of Clinical and Molecular Genetics, Vall d'Hebron University Hospital and Medicine Genetics Group, Vall d'Hebron Research Institute, Barcelona, Spain
| | - Anna Maria Cueto-González
- Department of Clinical and Molecular Genetics, Vall d'Hebron University Hospital and Medicine Genetics Group, Vall d'Hebron Research Institute, Barcelona, Spain
| | - Brian H Chhouk
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Rebecca C Yeh
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Jennifer E Neil
- Division of Genetics and Genomics and Howard Hughes Medical Institute, Boston Children's Hospital, Boston, Massachusetts, USA
| | | | - Tjitske Kleefstra
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Mariet W Elting
- Department of Human Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Andrea Császár
- Paediatric Ward, Hospital of Zala County, Zalaegerszeg, Hungary
| | - Judit Kárteszi
- Genetic Counselling, Hospital of Zala County, Zalaegerszeg, Hungary
| | - Beáta Bessenyei
- Division of Clinical Genetics, Department of Laboratory Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Hans van Bokhoven
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Paula Jorge
- Unidade de Genética Molecular, Centro de Genética Médica Doutor Jacinto de Magalhães (CGM), Centro Hospitalar Universitário do Porto (CHUPorto); Unit for Multidisciplinary Research In Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), and ITR - Laboratory for Integrative and Translational Research in Population Health, University of Porto, Porto, Portugal
| | - Johanna M van Hagen
- Department of Human Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Arjan P M de Brouwer
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, Nijmegen, The Netherlands
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Chang KT, Jezek J, Campbell AN, Stieg DC, Kiss ZA, Kemper K, Jiang P, Lee HO, Kruger WD, van Hasselt PM, Strich R. Aberrant cyclin C nuclear release induces mitochondrial fragmentation and dysfunction in MED13L syndrome fibroblasts. iScience 2022; 25:103823. [PMID: 35198885 PMCID: PMC8844603 DOI: 10.1016/j.isci.2022.103823] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 11/02/2021] [Accepted: 01/21/2022] [Indexed: 12/25/2022] Open
Abstract
MED13L syndrome is a haploinsufficiency developmental disorder characterized by intellectual disability, heart malformation, and hypotonia. MED13L controls transcription by tethering the cyclin C-Cdk8 kinase module (CKM) to the Mediator complex. In addition, cyclin C has CKM-independent roles in the cytoplasm directing stress-induced mitochondrial fragmentation and regulated cell death. Unstressed MED13L S1497 F/fs patient fibroblasts exhibited aberrant cytoplasmic cyclin C localization, mitochondrial fragmentation, and a 6-fold reduction in respiration. In addition, the fibroblasts exhibited reduced mtDNA copy number, reduction in mitochondrial membrane integrity, and hypersensitivity to oxidative stress. Finally, transcriptional analysis of MED13L mutant fibroblasts revealed reduced mRNA levels for several genes necessary for normal mitochondrial function. Pharmacological or genetic approaches preventing cyclin C-mitochondrial localization corrected the fragmented mitochondrial phenotype and partially restored organelle function. In conclusion, this study found that mitochondrial dysfunction is an underlying defect in cells harboring the MED13L S1497 F/fs allele and identified cyclin C mis-localization as the likely cause. These results provide a new avenue for understanding this disorder.
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Affiliation(s)
- Kai-Ti Chang
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Jan Jezek
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Alicia N Campbell
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - David C Stieg
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Zachary A Kiss
- Department of Medicine, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Kevin Kemper
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Ping Jiang
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Hyung-Ok Lee
- Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | | | - Peter M van Hasselt
- Department of Metabolic and Endocrine Disease, University of Utrecht Medical Center, Utrecht, 3584 CX, the Netherlands
| | - Randy Strich
- Department of Molecular Biology, Graduate School of Biomedical Sciences, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
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van de Plassche SR, de Brouwer APM. MED12-Related (Neuro)Developmental Disorders: A Question of Causality. Genes (Basel) 2021; 12:663. [PMID: 33925166 PMCID: PMC8146938 DOI: 10.3390/genes12050663] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 04/22/2021] [Accepted: 04/23/2021] [Indexed: 12/24/2022] Open
Abstract
MED12 is a member of the Mediator complex that is involved in the regulation of transcription. Missense variants in MED12 cause FG syndrome, Lujan-Fryns syndrome, and Ohdo syndrome, as well as non-syndromic intellectual disability (ID) in hemizygous males. Recently, female patients with de novo missense variants and de novo protein truncating variants in MED12 were described, resulting in a clinical spectrum centered around ID and Hardikar syndrome without ID. The missense variants are found throughout MED12, whether they are inherited in hemizygous males or de novo in females. They can result in syndromic or nonsyndromic ID. The de novo nonsense variants resulting in Hardikar syndrome that is characterized by facial clefting, pigmentary retinopathy, biliary anomalies, and intestinal malrotation, are found more N-terminally, whereas the more C-terminally positioned variants are de novo protein truncating variants that cause a severe, syndromic phenotype consisting of ID, facial dysmorphism, short stature, skeletal abnormalities, feeding difficulties, and variable other abnormalities. This broad range of distinct phenotypes calls for a method to distinguish between pathogenic and non-pathogenic variants in MED12. We propose an isogenic iNeuron model to establish the unique gene expression patterns that are associated with the specific MED12 variants. The discovery of these patterns would help in future diagnostics and determine the causality of the MED12 variants.
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Affiliation(s)
| | - Arjan P. M. de Brouwer
- Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands;
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Tian T, Cao X, Chen Y, Jin L, Li Z, Han X, Lin Y, Wlodarczyk BJ, Finnell RH, Yuan Z, Wang L, Ren A, Lei Y. Somatic and de novo Germline Variants of MEDs in Human Neural Tube Defects. Front Cell Dev Biol 2021; 9:641831. [PMID: 33748132 PMCID: PMC7969791 DOI: 10.3389/fcell.2021.641831] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/15/2021] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Neural tube defects (NTDs) are among the most common and severe congenital defects in humans. Their genetic etiology is complex and remains poorly understood. The Mediator complex (MED) plays a vital role in neural tube development in animal models. However, no studies have yet examined the role of its human homolog in the etiology of NTDs. METHODS In this study, 48 pairs of neural lesion site and umbilical cord tissues from NTD and 21 case-parent trios were involved in screening for NTD-related somatic and germline de novo variants. A series of functional cell assays were performed. We generated a Med12 p.Arg1784Cys knock-in mouse using CRISPR/Cas9 technology to validate the human findings. RESULTS One somatic variant, MED12 p.Arg1782Cys, was identified in the lesion site tissue from an NTD fetus. This variant was absent in any other normal tissue from different germ layers of the same case. In 21 case-parent trios, one de novo stop-gain variant, MED13L p.Arg1760∗, was identified. Cellular functional studies showed that MED12 p.Arg1782Cys decreased MED12 protein level and affected the regulation of MED12 on the canonical-WNT signaling pathway. The Med12 p.Arg1784Cys knock-in mouse exhibited exencephaly and spina bifida. CONCLUSION These findings provide strong evidence that functional variants of MED genes are associated with the etiology of some NTDs. We demonstrated a potentially important role for somatic variants in the occurrence of NTDs. Our study is the first study in which an NTD-related variant identified in humans was validated in mice using CRISPR/Cas9 technology.
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Affiliation(s)
- Tian Tian
- National Health Commission Key Laboratory of Reproductive Health, Institute of Reproductive and Child Health, Peking University, Beijing, China
- Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
| | - Xuanye Cao
- Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, United States
| | - Yongyan Chen
- National Health Commission Key Laboratory of Reproductive Health, Institute of Reproductive and Child Health, Peking University, Beijing, China
- Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
| | - Lei Jin
- National Health Commission Key Laboratory of Reproductive Health, Institute of Reproductive and Child Health, Peking University, Beijing, China
- Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
| | - Zhiwen Li
- National Health Commission Key Laboratory of Reproductive Health, Institute of Reproductive and Child Health, Peking University, Beijing, China
- Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
| | - Xiao Han
- Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, United States
| | - Ying Lin
- Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, United States
| | - Bogdan J. Wlodarczyk
- Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, United States
| | - Richard H. Finnell
- Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, United States
- Departments of Molecular and Human Genetics and Medicine, Baylor College of Medicine, Houston, TX, United States
| | - Zhengwei Yuan
- Key Laboratory of Health Ministry for Congenital Malformation, Shengjing Hospital, China Medical University, Shenyang, China
| | - Linlin Wang
- National Health Commission Key Laboratory of Reproductive Health, Institute of Reproductive and Child Health, Peking University, Beijing, China
- Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
| | - Aiguo Ren
- National Health Commission Key Laboratory of Reproductive Health, Institute of Reproductive and Child Health, Peking University, Beijing, China
- Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
| | - Yunping Lei
- Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, United States
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De novo variants in MED12 cause X-linked syndromic neurodevelopmental disorders in 18 females. Genet Med 2020; 23:645-652. [DOI: 10.1038/s41436-020-01040-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 11/01/2020] [Accepted: 11/02/2020] [Indexed: 11/08/2022] Open
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De novo loss-of-function variants in X-linked MED12 are associated with Hardikar syndrome in females. Genet Med 2020; 23:637-644. [PMID: 33244166 DOI: 10.1038/s41436-020-01031-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 10/15/2020] [Indexed: 12/21/2022] Open
Abstract
PURPOSE Hardikar syndrome (MIM 612726) is a rare multiple congenital anomaly syndrome characterized by facial clefting, pigmentary retinopathy, biliary anomalies, and intestinal malrotation, but with preserved cognition. Only four patients have been reported previously, and none had a molecular diagnosis. Our objective was to identify the genetic basis of Hardikar syndrome (HS) and expand the phenotypic spectrum of this disorder. METHODS We performed exome sequencing on two previously reported and five unpublished female patients with a clinical diagnosis of HS. X-chromosome inactivation (XCI) studies were also performed. RESULTS We report clinical features of HS with previously undescribed phenotypes, including a fatal unprovoked intracranial hemorrhage at age 21. We additionally report the discovery of de novo pathogenic nonsense and frameshift variants in MED12 in these seven individuals and evidence of extremely skewed XCI in all patients with informative testing. CONCLUSION Pathogenic missense variants in the X-chromosome gene MED12 have previously been associated with Opitz-Kaveggia syndrome, Lujan syndrome, Ohdo syndrome, and nonsyndromic intellectual disability, primarily in males. We propose a fifth, female-specific phenotype for MED12, and suggest that nonsense and frameshift loss-of-function MED12 variants in females cause HS. This expands the MED12-associated phenotype in females beyond intellectual disability.
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Wang C, Lin L, Xue Y, Wang Y, Liu Z, Ou Z, Wu S, Lan X, Zhang Y, Yuan F, Luo X, Wang C, Xi J, Sun X, Chen Y. MED12-Related Disease in a Chinese Girl: Clinical Characteristics and Underlying Mechanism. Front Genet 2020; 11:129. [PMID: 32174975 PMCID: PMC7056888 DOI: 10.3389/fgene.2020.00129] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 02/03/2020] [Indexed: 11/13/2022] Open
Abstract
The RNA polymerase II transcription subunit 12 homolog (MED12) is a member of the mediator complex, which plays a critical role in RNA transcription. Mutations in MED12 cause X-linked intellectual disability and other anomalies collectively grouped as MED12-related disorders. While MED12 mutations have been most commonly reported in male patients, we present the case of a 1-year-old girl with clinical characteristics similar to MED12-related disorders. To explore the clinical characteristics of the condition and its possible pathogenesis, we analyzed the patient's clinical data; genetic testing by whole-exome sequencing revealed a de novo heterozygous mutation (c.1249-1G > C) in MED12. Further cDNA experiments revealed that the patient had an abnormal splicing at the skipping of exon9, which may have produced a truncated protein. qPCR showed decreased MED12 gene expression level in the patient, and an X-chromosome inactivation test confirmed a skewed inactivation of the X-chromosome. The lymphoblast transcription levels of the genes involved in the Gli3-dependent sonic hedgehog (SHH) signaling pathway, namely, CREB5, BMP4, and NEUROG2, were found to be significantly elevated compared with those of her parents and sex- and age-matched controls. Our results support the view that MED12 mutations may dysregulate the SHH signaling pathway, which may have accounted for the aberrant craniofacial morphology of our patient.
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Affiliation(s)
- Chao Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Longlong Lin
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Yan Xue
- Institute of Medical Science, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yilin Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Zhao Liu
- Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL, United States
| | - Zicheng Ou
- Department of Pediatrics, JianNing General Hospital, Fujian, China
| | - Shengnan Wu
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaoping Lan
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Yuanfeng Zhang
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Fang Yuan
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaona Luo
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Chunmei Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Jiaming Xi
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaomin Sun
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Yucai Chen
- Department of Neurology, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
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Tejada MI, Ibarluzea N. Non-syndromic X linked intellectual disability: Current knowledge in light of the recent advances in molecular and functional studies. Clin Genet 2020; 97:677-687. [PMID: 31898314 DOI: 10.1111/cge.13698] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 12/09/2019] [Accepted: 12/24/2019] [Indexed: 12/23/2022]
Abstract
Since the discovery of the FMR1 gene and the clinical and molecular characterization of Fragile X Syndrome in 1991, more than 141 genes have been identified in the X-chromosome in these 28 years thanks to applying continuously evolving molecular techniques to X-linked intellectual disability (XLID) families. In the past decade, array comparative genomic hybridization and next generation sequencing technologies have accelerated gene discovery exponentially. Classically, XLID has been subdivided in syndromic intellectual disability (S-XLID)-where intellectual disability (ID) is always associated with other recognizable physical and/or neurological features-and non-specific or non-syndromic intellectual disability (NS-XLID) where the only common feature is ID. Nevertheless, new advances on the study of these entities have showed that this classification is not always clear-cut because distinct variants in several of these XLID genes can result in S-XLID as well as in NS-XLID. This review focuses on the current knowledge on the XLID genes involved in non-syndromic forms, with the emphasis on their pathogenic mechanism, thus allowing the possibility to elucidate why some of them can give both syndromic and non-syndromic phenotypes.
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Affiliation(s)
- María Isabel Tejada
- Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, Barakaldo, Spain.,Biocruces-Bizkaia Health Research Institute, Barakaldo, Spain.,Clinical Group, Centre for Biomedical Research on Rare Diseases (CIBERER), Valencia, Spain
| | - Nekane Ibarluzea
- Biocruces-Bizkaia Health Research Institute, Barakaldo, Spain.,Clinical Group, Centre for Biomedical Research on Rare Diseases (CIBERER), Valencia, Spain
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Poot M. Mutations in Mediator Complex Genes CDK8, MED12, MED13, and MEDL13 Mediate Overlapping Developmental Syndromes. Mol Syndromol 2019; 10:239-242. [PMID: 32021594 DOI: 10.1159/000502346] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2019] [Indexed: 12/18/2022] Open
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10
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Srivastava S, Niranjan T, May MM, Tarpey P, Allen W, Hackett A, Jouk P, Raymond L, Briault S, Skinner C, Toutain A, Gecz J, Heath W, Stevenson RE, Schwartz CE, Wang T. Dysregulations of sonic hedgehog signaling in MED12-related X-linked intellectual disability disorders. Mol Genet Genomic Med 2019; 7:e00569. [PMID: 30729724 PMCID: PMC6465656 DOI: 10.1002/mgg3.569] [Citation(s) in RCA: 10] [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: 07/20/2018] [Revised: 12/05/2018] [Accepted: 12/11/2018] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Mutations in mediator of RNA polymerase II transcription subunit 12 homolog (MED12, OMIM 300188) cause X-linked intellectual disability (XLID) disorders including FG, Lujan, and Ohdo syndromes. The Gli3-dependent Sonic Hedgehog (SHH) signaling pathway has been implicated in the original FG syndrome and Lujan syndrome. How are SHH-signaling defects related to the complex clinical phenotype of MED12-associated XLID syndromes are not fully understood. METHODS Quantitative RT-PCR was used to study expression levels of three SHH-signaling genes in lymophoblast cell lines carrying four MED12 mutations from four unrelated XLID families. Genotype and phenotype correlation studies were performed on these mutations. RESULTS Three newly identified and one novel MED12 mutations in six affected males from four unrelated XLID families were studied. Three mutations (c.2692A>G; p.N898D, c.3640C>T; p.R1214C, and c.3884G>A; p.R1295H) are located in the LS domain and one (c.617G>A; p.R206Q) is in the L domain of MED12. These mutations involve highly conserved amino acid residues and segregate with ID and related congenital malformations in respective probands families. Patients with the LS-domain mutations share many features of FG syndrome and some features of Lujan syndrome. The patient with the L-domain mutation presented with ID and predominant neuropsychiatric features but little dysmorphic features of either FG or Lujan syndrome. Transcript levels of three Gli3-dependent SHH-signaling genes, CREB5, BMP4, and NEUROG2, were determined by quantitative RT-PCR and found to be significantly elevated in lymphoblasts from patients with three mutations in the MED12-LS domain. CONCLUSIONS These results support a critical role of MED12 in regulating Gli3-dependent SHH signaling and in developing ID and related congenital malformations in XLID syndromes. Differences in the expression profile of SHH-signaling genes potentially contribute to variability in clinical phenotypes in patients with MED12-related XLID disorders.
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Affiliation(s)
- Siddharth Srivastava
- Institute of Genetic Medicine and Department of PediatricsJohns Hopkins UniversityBaltimoreMaryland
| | - Tejasvi Niranjan
- Institute of Genetic Medicine and Department of PediatricsJohns Hopkins UniversityBaltimoreMaryland
| | | | | | | | - Anna Hackett
- Genetics of Learning Disability ServiceHunter GeneticsWaratahNSWAustralia
| | | | - Lucy Raymond
- Cambridge Institute of Medical ResearchCambridgeUK
| | | | | | - Annick Toutain
- Service de Génétique Clinique, Hôpital BretonneauToursFrance
| | - Jozef Gecz
- Adelaide Medical School and Robinson Research InstituteThe University of AdelaideAdelaideAustralia
| | - William Heath
- J.I. Riddle Developmental CenterMorgantonNorth Carolina
| | | | | | - Tao Wang
- Institute of Genetic Medicine and Department of PediatricsJohns Hopkins UniversityBaltimoreMaryland
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