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Rahikkala E, Urpa L, Ghimire B, Topa H, Kurki MI, Koskela M, Airavaara M, Hämäläinen E, Pylkäs K, Körkkö J, Savolainen H, Suoranta A, Bertoli-Avella A, Rolfs A, Mattila P, Daly M, Palotie A, Pietiläinen O, Moilanen J, Kuismin O. A novel variant in SMG9 causes intellectual disability, confirming a role for nonsense-mediated decay components in neurocognitive development. Eur J Hum Genet 2022; 30:619-627. [PMID: 35087184 PMCID: PMC9090808 DOI: 10.1038/s41431-022-01046-5] [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: 07/13/2021] [Revised: 12/04/2021] [Accepted: 01/11/2022] [Indexed: 12/13/2022] Open
Abstract
Biallelic loss-of-function variants in the SMG9 gene, encoding a regulatory subunit of the mRNA nonsense-mediated decay (NMD) machinery, are reported to cause heart and brain malformation syndrome. Here we report five patients from three unrelated families with intellectual disability (ID) and a novel pathogenic SMG9 c.551 T > C p.(Val184Ala) homozygous missense variant, identified using exome sequencing. Sanger sequencing confirmed recessive segregation in each family. SMG9 c.551T > C p.(Val184Ala) is most likely an autozygous variant identical by descent. Characteristic clinical findings in patients were mild to moderate ID, intention tremor, pyramidal signs, dyspraxia, and ocular manifestations. We used RNA sequencing of patients and age- and sex-matched healthy controls to assess the effect of the variant. RNA sequencing revealed that the SMG9 c.551T > C variant did not affect the splicing or expression level of SMG9 gene products, and allele-specific expression analysis did not provide evidence that the nonsense mRNA-induced NMD was affected. Differential gene expression analysis identified prevalent upregulation of genes in patients, including the genes SMOX, OSBP2, GPX3, and ZNF155. These findings suggest that normal SMG9 function may be involved in transcriptional regulation without affecting nonsense mRNA-induced NMD. In conclusion, we demonstrate that the SMG9 c.551T > C missense variant causes a neurodevelopmental disorder and impacts gene expression. NMD components have roles beyond aberrant mRNA degradation that are crucial for neurocognitive development.
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Affiliation(s)
- Elisa Rahikkala
- Department of Clinical Genetics, PEDEGO Research Unit and Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
- Institute of Biomedicine, University of Turku, Turku, Finland.
| | - Lea Urpa
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Bishwa Ghimire
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Hande Topa
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Mitja I Kurki
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
- Psychiatric & Neurodevelopmental Genetics Unit, Massachusetts General Hospital, Boston, MA, USA
- The Stanley Center for Psychiatric Research, The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Maryna Koskela
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Mikko Airavaara
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
- Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Eija Hämäläinen
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Katri Pylkäs
- Cancer and Translational Medicine Research Unit and Biocenter Oulu, University of Oulu, NordLab Oulu, Oulu, Finland
| | - Jarmo Körkkö
- Center for Intellectual Disability Care, Oulu University Hospital, Oulu, Finland
| | - Helena Savolainen
- Center for Intellectual Disability Care, Oulu University Hospital, Oulu, Finland
| | - Anu Suoranta
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | | | - Arndt Rolfs
- Centogene GmbH, 18055, Rostock, Germany
- Medical Faculty, University of Rostock, Rostock, Germany
| | - Pirkko Mattila
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Mark Daly
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
- Psychiatric & Neurodevelopmental Genetics Unit, Massachusetts General Hospital, Boston, MA, USA
- The Stanley Center for Psychiatric Research, The Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Analytic and Translational Genetics Unit, Department of Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Aarno Palotie
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
- Psychiatric & Neurodevelopmental Genetics Unit, Massachusetts General Hospital, Boston, MA, USA
- The Stanley Center for Psychiatric Research, The Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Analytic and Translational Genetics Unit, Department of Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Olli Pietiläinen
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
- The Stanley Center for Psychiatric Research, The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Jukka Moilanen
- Department of Clinical Genetics, PEDEGO Research Unit and Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
| | - Outi Kuismin
- Department of Clinical Genetics, PEDEGO Research Unit and Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
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Yang Q, Qin Z, Zhang Q, Yi S, Yi S, Luo J. Identification of a novel compound heterozygous SMG9 variants in a Chinese family with heart and brain malformation syndrome using whole exome sequencing. BMC Med Genomics 2022; 15:67. [PMID: 35321723 PMCID: PMC8943999 DOI: 10.1186/s12920-022-01217-9] [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: 01/18/2022] [Accepted: 03/17/2022] [Indexed: 11/13/2022] Open
Abstract
SMG9-deficiency syndrome, also known as heart and brain malformation syndrome, is a very rare congenital genetic disorder mainly characterized by brain, heart, and growth and developmental abnormalities. This syndrome is an autosomal recessive disease resulting from mutations in the SMG9 gene, which encodes a critical component of nonsense-mediated mRNA decay. Thus far, only twelve SMG9 deficiency patients have been reported with five novel homozygous SMG9 mutations. The most frequent characteristic features of these patients are facial dysmorphism, severe global developmental delay, intellectual disability, congenital heart disease, growth restriction, microcephaly, and brain abnormalities. Herein, whole exome sequencing was performed to identify novel compound heterozygous SMG9 variants (NM_019108.3: c.1318_1319delAG (p.Ser440*) and c.947A>G (p.His316Arg)) in the proband, who exhibited syndromic intellectual disability. Mutations were confirmed as segregating in his affected sister and other unaffected family members by Sanger sequencing. The patients we describe here have a similar dysmorphology profile associated with SMG9-deficiency syndrome. Comparing the phenotype with that of patients in published reports, our patients can walk independently and their growth parameters are normal. In addition, short stature, failure to thrive, and microcephaly were not observed. Possible residual function of the H316R SMG9 variant could explain the milder phenotype observed in our patients. Our report is the first description of a non-consanguineous Chinese pedigree with novel compound heterozygous variants in the SMG9 gene. The molecular confirmation of the patient expands the genetic spectrum of SMG9-deficiency syndrome, and the manifestation of SMG9-deficiency syndrome in the patient provides additional clinical information regarding this syndrome.
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Affiliation(s)
- Qi Yang
- Guangxi Key Laboratory of Birth Defects Research and Prevention, Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, No. 59, Xiangzhu Road, Nanning, China.,Department of Genetic and Metabolic Central Laboratory, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Zailong Qin
- Guangxi Key Laboratory of Birth Defects Research and Prevention, Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, No. 59, Xiangzhu Road, Nanning, China.,Department of Genetic and Metabolic Central Laboratory, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Qinle Zhang
- Guangxi Key Laboratory of Birth Defects Research and Prevention, Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, No. 59, Xiangzhu Road, Nanning, China.,Department of Genetic and Metabolic Central Laboratory, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Shang Yi
- Guangxi Key Laboratory of Birth Defects Research and Prevention, Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, No. 59, Xiangzhu Road, Nanning, China.,Department of Genetic and Metabolic Central Laboratory, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Sheng Yi
- Guangxi Key Laboratory of Birth Defects Research and Prevention, Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, No. 59, Xiangzhu Road, Nanning, China.,Department of Genetic and Metabolic Central Laboratory, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China
| | - Jingsi Luo
- Guangxi Key Laboratory of Birth Defects Research and Prevention, Guangxi Key Laboratory of Reproductive Health and Birth Defects Prevention, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, No. 59, Xiangzhu Road, Nanning, China. .,Department of Genetic and Metabolic Central Laboratory, Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region, Nanning, China.
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Abdel-Salam GMH, Duan R, Abdel-Hamid MS, Sayed ISM, Jhangiani SN, Khan Z, Du H, Gibbs RA, Posey JE, Marafi D, Lupski JR. Expanding the phenotypic and allelic spectrum of SMG8: Clinical observations reveal overlap with SMG9-associated disease trait. Am J Med Genet A 2021; 188:648-657. [PMID: 34761517 DOI: 10.1002/ajmg.a.62561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 10/03/2021] [Accepted: 10/22/2021] [Indexed: 11/06/2022]
Abstract
SMG8 (MIM *617315) is a regulatory subunit involved in nonsense-mediated mRNA decay (NMD), a cellular protective pathway that regulates mRNA transcription, transcript stability, and degrades transcripts containing premature stop codons. SMG8 binds SMG9 and SMG1 to form the SMG1C complex and inhibit the kinase activity of SMG1. Biallelic deleterious variants in SMG9 are known to cause a heart and brain malformation syndrome (HBMS; MIM #616920), whereas biallelic deleterious variants in SMG8 were recently described to cause a novel neurodevelopmental disorder (NDD) with dysmorphic facies and cataracts, now defined as Alzahrani-Kuwahara syndrome (ALKUS: MIM #619268). Only eight subjects from four families with ALKUS have been described to date. Through research reanalysis of a nondiagnostic clinical exome, we identified a subject from a fifth unrelated family with a homozygous deleterious variant in SMG8 and features consistent with ALKUS. Interestingly, the subject also had unilateral microphthalmia, a clinical feature that has been described in SMG9-related disorder. Our study expands the phenotypic spectrum of SMG8-related disorder, demonstrates an overlapping phenotype between SMG8- and SMG9-related rare disease traits, provides further evidence for the SMG8 and SMG9 protein interactions, and highlights the importance of revisiting nondiagnostic exome data to identify and affirm emerging novel genes for rare disease traits.
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Affiliation(s)
- Ghada M H Abdel-Salam
- Clinical Genetics Department, Human Genetics and Genome Research Division, National ResearchCentre, Cairo, Egypt
| | - Ruizhi Duan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Mohamed S Abdel-Hamid
- Medical Molecular Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Inas S M Sayed
- Orodental Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Shalini N Jhangiani
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA
| | - Ziad Khan
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA
| | - Haowei Du
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Richard A Gibbs
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.,Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA
| | - Jennifer E Posey
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Dana Marafi
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.,Department of Pediatrics, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - James R Lupski
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.,Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas, USA.,Texas Children's Hospital, Houston, Texas, USA.,Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
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4
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Altuwaijri N, Abdelbaky M, Alhashem A, Alrakaf M, Hashem M, Alzahrani F, Alkuraya FS. Further delineation of SMG9-related heart and brain malformation syndrome. Am J Med Genet A 2021; 185:1624-1630. [PMID: 33609422 DOI: 10.1002/ajmg.a.62139] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/08/2021] [Accepted: 02/08/2021] [Indexed: 11/05/2022]
Affiliation(s)
- Norah Altuwaijri
- Department of Translational Genomics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Mona Abdelbaky
- Department of Pediatrics, Prince Sultan Medical Military City, Riyadh, Saudi Arabia
| | - Amal Alhashem
- Department of Pediatrics, Prince Sultan Medical Military City, Riyadh, Saudi Arabia.,Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
| | - Maha Alrakaf
- Department of Obstetrics and Gynecology, Maternal fetal Medicine Division, Prince Sultan Medical Military City, Riyadh, Saudi Arabia
| | - Mais Hashem
- Department of Translational Genomics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Fatema Alzahrani
- Department of Translational Genomics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Fowzan S Alkuraya
- Department of Translational Genomics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.,Department of Pediatrics, Prince Sultan Medical Military City, Riyadh, Saudi Arabia.,Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
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Alzahrani F, Kuwahara H, Long Y, Al-Owain M, Tohary M, AlSayed M, Mahnashi M, Fathi L, Alnemer M, Al-Hamed MH, Lemire G, Boycott KM, Hashem M, Han W, Al-Maawali A, Al Mahrizi F, Al-Thihli K, Gao X, Alkuraya FS. Recessive, Deleterious Variants in SMG8 Expand the Role of Nonsense-Mediated Decay in Developmental Disorders in Humans. Am J Hum Genet 2020; 107:1178-1185. [PMID: 33242396 DOI: 10.1016/j.ajhg.2020.11.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 11/04/2020] [Indexed: 12/16/2022] Open
Abstract
We have previously described a heart-, eye-, and brain-malformation syndrome caused by homozygous loss-of-function variants in SMG9, which encodes a critical component of the nonsense-mediated decay (NMD) machinery. Here, we describe four consanguineous families with four different likely deleterious homozygous variants in SMG8, encoding a binding partner of SMG9. The observed phenotype greatly resembles that linked to SMG9 and comprises severe global developmental delay, microcephaly, facial dysmorphism, and variable congenital heart and eye malformations. RNA-seq analysis revealed a general increase in mRNA expression levels with significant overrepresentation of core NMD substrates. We also identified increased phosphorylation of UPF1, a key SMG1-dependent step in NMD, which most likely represents the loss of SMG8--mediated inhibition of SMG1 kinase activity. Our data show that SMG8 and SMG9 deficiency results in overlapping developmental disorders that most likely converge mechanistically on impaired NMD.
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