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Rodrigues Alves Barbosa V, Maroilley T, Diao C, Colvin-James L, Perrier R, Tarailo-Graovac M. Single variant, yet "double trouble": TSC and KBG syndrome because of a large de novo inversion. Life Sci Alliance 2024; 7:e202302115. [PMID: 38253421 PMCID: PMC10803213 DOI: 10.26508/lsa.202302115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 01/24/2024] Open
Abstract
Despite the advances in high-throughput sequencing, many rare disease patients remain undiagnosed. In particular, the patients with well-defined clinical phenotypes and established clinical diagnosis, yet missing or partial genetic diagnosis, may hold a clue to more complex genetic mechanisms of a disease that could be missed by available clinical tests. Here, we report a patient with a clinical diagnosis of Tuberous sclerosis, combined with unusual secondary features, but negative clinical tests including TSC1 and TSC2 Short-read whole-genome sequencing combined with advanced bioinformatics analyses were successful in uncovering a de novo pericentric 87-Mb inversion with breakpoints in TSC2 and ANKRD11, which explains the TSC clinical diagnosis, and confirms a second underlying monogenic disorder, KBG syndrome. Our findings illustrate how complex variants, such as large inversions, may be missed by clinical tests and further highlight the importance of well-defined clinical diagnoses in uncovering complex molecular mechanisms of a disease, such as complex variants and "double trouble" effects.
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Affiliation(s)
- Victoria Rodrigues Alves Barbosa
- https://ror.org/03yjb2x39 Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
| | - Tatiana Maroilley
- https://ror.org/03yjb2x39 Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
| | - Catherine Diao
- https://ror.org/03yjb2x39 Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
| | - Leslie Colvin-James
- https://ror.org/03yjb2x39 Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
| | - Renee Perrier
- https://ror.org/03yjb2x39 Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
| | - Maja Tarailo-Graovac
- https://ror.org/03yjb2x39 Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada
- https://ror.org/03yjb2x39 Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
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Maroilley T, Tsai MH, Mascarenhas R, Diao C, Khanbabaei M, Kaya S, Depienne C, Tarailo-Graovac M, Klein KM. A novel FAME1 repeat configuration in a European family identified using a combined genomics approach. Epilepsia Open 2023. [PMID: 36740228 DOI: 10.1002/epi4.12702] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 01/28/2023] [Indexed: 02/07/2023] Open
Abstract
Familial adult myoclonic epilepsy (FAME) is an adult-onset neurological disease characterized by cortical tremor, myoclonus, and seizures due to a pentanucleotide repeat expansion: a combination of pathogenic TTTCA expansion associated with a TTTTA repeat in introns of six different genes. Repeat-primed PCR (RP-PCR) is an inexpensive test for expansions at known loci. The analysis of the SAMD12 locus revealed that the repeats have different size, configuration, and composition. The TTTCA repeats can be very long (>1000 repeats) but also very short (14 being the shortest identified). Here, we report siblings of European descent with the clinical diagnosis of FAME yet a negative RP-PCR test. Using short-read genome sequencing, we identified the pentanucleotide expansion in intron 4 of SAMD12, which was confirmed by CRIPSR-Cas9-mediated enrichment and long-read sequencing to be of (TTTTA)~879 (TTTCA)3 (TTTTA)7 (TTTCA)7 configuration. Our finding is the first to associate the SAMD12 locus in European patients with FAME and currently represents the shortest identified TTTCA expansion. Our results suggest that the SAMD12 locus should be tested in patients with suspected FAME independent of ethnicity. Furthermore, RP-PCR may miss the underlying mutation, and genome sequencing may be needed to confirm the pathogenic repeat.
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Affiliation(s)
- Tatiana Maroilley
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Meng-Han Tsai
- Department of Neurology and Medical Research, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.,School of Medicine, College of Medicine, Taoyuan, Chang Gung University, Taoyuan City, Taiwan
| | - Rumika Mascarenhas
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Catherine Diao
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Maryam Khanbabaei
- Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada
| | - Sabine Kaya
- Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Christel Depienne
- Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Maja Tarailo-Graovac
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Karl Martin Klein
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.,Epilepsy Center Frankfurt Rhine-Main, Department of Neurology, Center of Neurology and Neurosurgery, University Hospital, Center for Personalized Translational Epilepsy Research (CePTER), Goethe-University Frankfurt, Frankfurt, Germany
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Sarkar A, Panati K, Narala VR. Code inside the codon: The role of synonymous mutations in regulating splicing machinery and its impact on disease. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2022; 790:108444. [PMID: 36307006 DOI: 10.1016/j.mrrev.2022.108444] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 10/10/2022] [Accepted: 10/21/2022] [Indexed: 11/06/2022]
Abstract
In eukaryotes, precise pre-mRNA processing, including alternative splicing, is essential to carry out the intricate protein translation process. Both point mutations (that alter the translated protein sequence) and synonymous mutations (that do not alter the translated protein sequence) are capable of affecting the splicing process. Synonymous mutations are known to affect gene expression via altering mRNA stability, mRNA secondary structure, splicing processes, and translational kinetics. In higher eukaryotes, precise splicing is regulated by three weakly conserved cis-elements, 5' and 3' splice sites and the branch site. Many other cis-acting elements (exonic/intronic splicing enhancers and silencers) and trans-acting splicing factors (serine and arginine-rich proteins and heterogeneous nuclear ribonucleoproteins) have also been found to enhance or suppress the splicing process. The appearance of synonymous mutations in cis-acting elements can alter the splicing process by changing the binding pattern of splicing factors to exonic splicing enhancers or silencer motifs. This results in exon skipping, intron retention, and various other forms of alternative splicing, eventually leading to the emergence of a wide range of diseases. The focus of this review is to elucidate the role of synonymous mutations and their impact on abnormal splicing mechanisms. Further, this study highlights the function of synonymous mutation in mediating abnormal splicing in cancer and development of X-linked, and autosomal inherited diseases.
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Affiliation(s)
- Avik Sarkar
- Department of Zoology, Vidyasagar University, Midnapore, West Bengal 721102, India
| | - Kalpana Panati
- Department of Biotechnology, Government College for Men, Kadapa 516004, India
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