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Elert-Dobkowska E, Stepniak I, Radziwonik-Fraczyk W, Jahic A, Beetz C, Sulek A. SPAST Intragenic CNVs Lead to Hereditary Spastic Paraplegia via a Haploinsufficiency Mechanism. Int J Mol Sci 2024; 25:5008. [PMID: 38732227 PMCID: PMC11084448 DOI: 10.3390/ijms25095008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 04/26/2024] [Accepted: 04/30/2024] [Indexed: 05/13/2024] Open
Abstract
The most common form of hereditary spastic paraplegia (HSP), SPG4 is caused by single nucleotide variants and microrearrangements in the SPAST gene. The high percentage of multi-exonic deletions or duplications observed in SPG4 patients is predisposed by the presence of a high frequency of Alu sequences in the gene sequence. In the present study, we analyzed DNA and RNA samples collected from patients with different microrearrangements in SPAST to map gene breakpoints and evaluate the mutation mechanism. The study group consisted of 69 individuals, including 50 SPG4 patients and 19 healthy relatives from 18 families. Affected family members from 17 families carried varying ranges of microrearrangements in the SPAST gene, while one individual had a single nucleotide variant in the 5'UTR of SPAST. To detect the breakpoints of the SPAST gene, long-range PCR followed by sequencing was performed. The breakpoint sequence was detected for five different intragenic SPAST deletions and one duplication, revealing Alu-mediated microhomology at breakpoint junctions resulting from non-allelic homologous recombination in these patients. Furthermore, SPAST gene expression analysis was performed using patient RNA samples extracted from whole blood. Quantitative real-time PCR tests performed in 14 patients suggest no expression of transcripts with microrearrangements in 5 of them. The obtained data indicate that nonsense-mediated decay degradation is not the only mechanism of hereditary spastic paraplegia in patients with SPAST microrearrangements.
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Affiliation(s)
- Ewelina Elert-Dobkowska
- Department of Genetics, Institute of Psychiatry and Neurology, 02-957 Warsaw, Poland; (E.E.-D.); (I.S.); (W.R.-F.)
| | - Iwona Stepniak
- Department of Genetics, Institute of Psychiatry and Neurology, 02-957 Warsaw, Poland; (E.E.-D.); (I.S.); (W.R.-F.)
| | - Wiktoria Radziwonik-Fraczyk
- Department of Genetics, Institute of Psychiatry and Neurology, 02-957 Warsaw, Poland; (E.E.-D.); (I.S.); (W.R.-F.)
| | - Amir Jahic
- Institute of Diagnostic Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Charité–Universitätsmedizin, 10117 Berlin, Germany;
| | - Christian Beetz
- Department of Chemistry and Laboratory Medicine, Jena University Hospital, 07747 Jena, Germany;
- Centogene, 18055 Rostock, Germany
| | - Anna Sulek
- Faculty of Medicine, Lazarski University, 02-662 Warsaw, Poland
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2
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Chen YJ, Wang MW, Qiu YS, Yuan RY, Wang N, Lin X, Chen WJ. Alu Retrotransposition Event in SPAST Gene as a Novel Cause of Hereditary Spastic Paraplegia. Mov Disord 2023; 38:1750-1755. [PMID: 37394769 DOI: 10.1002/mds.29522] [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: 01/31/2023] [Revised: 06/05/2023] [Accepted: 06/12/2023] [Indexed: 07/04/2023] Open
Abstract
OBJECTIVES To diagnose the molecular cause of hereditary spastic paraplegia (HSP) observed in a four-generation family with autosomal dominant inheritance. METHODS Multiplex ligation-dependent probe amplification (MLPA), whole-exome sequencing (WES), and RNA sequencing (RNA-seq) of peripheral blood leukocytes were performed. Reverse transcription polymerase chain reaction (RT-PCR) and Sanger sequencing were used to characterize target regions of SPAST. RESULTS A 121-bp AluYb9 insertion with a 30-bp poly-A tail flanked by 15-bp direct repeats on both sides was identified in the edge of intron 16 in SPAST that segregated with the disease phenotype. CONCLUSIONS We identified an intronic AluYb9 insertion inducing splicing alteration in SPAST causing pure HSP phenotype that was not detected by routine WES analysis. Our findings suggest RNA-seq is a recommended implementation for undiagnosed cases by first-line diagnostic approaches. © 2023 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Yi-Jun Chen
- Department of Neurology and Institute of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
- Department of Geriatrics, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
- Department of Geriatrics, National Regional Medical Center, Binhai Campus of the First Affiliated Hospital, Fujian Medical University, Fuzhou, China
| | - Meng-Wen Wang
- Department of Neurology and Institute of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Yu-Sen Qiu
- Department of Neurology and Institute of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Ru-Ying Yuan
- Department of Neurology and Institute of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Ning Wang
- Department of Neurology and Institute of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
| | - Xiang Lin
- Department of Neurology and Institute of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
| | - Wan-Jin Chen
- Department of Neurology and Institute of Neurology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Molecular Neurology, Fujian Medical University, Fuzhou, China
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3
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Pinto A, Cunha C, Chaves R, Butchbach MER, Adega F. Comprehensive In Silico Analysis of Retrotransposon Insertions within the Survival Motor Neuron Genes Involved in Spinal Muscular Atrophy. BIOLOGY 2022; 11:824. [PMID: 35741345 PMCID: PMC9219815 DOI: 10.3390/biology11060824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 05/19/2022] [Accepted: 05/25/2022] [Indexed: 11/16/2022]
Abstract
Transposable elements (TEs) are interspersed repetitive and mobile DNA sequences within the genome. Better tools for evaluating TE-derived sequences have provided insights into the contribution of TEs to human development and disease. Spinal muscular atrophy (SMA) is an autosomal recessive motor neuron disease that is caused by deletions or mutations in the Survival Motor Neuron 1 (SMN1) gene but retention of its nearly perfect orthologue SMN2. Both genes are highly enriched in TEs. To establish a link between TEs and SMA, we conducted a comprehensive, in silico analysis of TE insertions within the SMN1/2 loci of SMA, carrier and healthy genomes. We found an Alu insertion in the promoter region and one L1 element in the 3'UTR that may play an important role in alternative promoter as well as in alternative transcriptional termination. Additionally, several intronic Alu repeats may influence alternative splicing via RNA circularization and causes the presence of new alternative exons. These Alu repeats present throughout the genes are also prone to recombination events that could lead to SMN1 exons deletions and, ultimately, SMA. TE characterization of the SMA genomic region could provide for a better understanding of the implications of TEs on human disease and genomic evolution.
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Affiliation(s)
- Albano Pinto
- Laboratory of Cytogenomics and Animal Genomics (CAG), Department of Genetics and Biotechnology (DGB), University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal; (A.P.); (C.C.); (R.C.)
- BioISI-Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, 1749-016 Lisbon, Portugal
| | - Catarina Cunha
- Laboratory of Cytogenomics and Animal Genomics (CAG), Department of Genetics and Biotechnology (DGB), University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal; (A.P.); (C.C.); (R.C.)
- BioISI-Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, 1749-016 Lisbon, Portugal
| | - Raquel Chaves
- Laboratory of Cytogenomics and Animal Genomics (CAG), Department of Genetics and Biotechnology (DGB), University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal; (A.P.); (C.C.); (R.C.)
- BioISI-Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, 1749-016 Lisbon, Portugal
| | - Matthew E. R. Butchbach
- Division of Neurology, Nemours Children’s Hospital Delaware, Wilmington, DE 19803, USA;
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
- Department of Pediatrics, Sidney Kimmel College of Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Filomena Adega
- Laboratory of Cytogenomics and Animal Genomics (CAG), Department of Genetics and Biotechnology (DGB), University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal; (A.P.); (C.C.); (R.C.)
- BioISI-Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, 1749-016 Lisbon, Portugal
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4
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Prakrithi P, Singhal K, Sharma D, Jain A, Bhoyar RC, Imran M, Senthilvel V, Divakar MK, Mishra A, Scaria V, Sivasubbu S, Mukerji M. An Alu insertion map of the Indian population: identification and analysis in 1021 genomes of the IndiGen project. NAR Genom Bioinform 2022; 4:lqac009. [PMID: 35178516 PMCID: PMC8846365 DOI: 10.1093/nargab/lqac009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 12/21/2021] [Accepted: 01/25/2022] [Indexed: 11/14/2022] Open
Abstract
Abstract
Actively retrotransposing primate-specific Alu repeats display insertion-deletion (InDel) polymorphism through their insertion at new loci. In the global datasets, Indian populations remain under-represented and so do their Alu InDels. Here, we report the genomic landscape of Alu InDels from the recently released 1021 Indian Genomes (IndiGen) (available at https://clingen.igib.res.in/indigen). We identified 9239 polymorphic Alu insertions that include private (3831), rare (3974) and common (1434) insertions with an average of 770 insertions per individual. We achieved an 89% PCR validation of the predicted genotypes in 94 samples tested. About 60% of identified InDels are unique to IndiGen when compared to other global datasets; 23% of sites were shared with both SGDP and HGSVC; among these, 58% (1289 sites) were common polymorphisms in IndiGen. The insertions not only show a bias for genic regions, with a preference for introns but also for the associated genes showing enrichment for processes like cell morphogenesis and neurogenesis (P-value < 0.05). Approximately, 60% of InDels mapped to genes present in the OMIM database. Finally, we show that 558 InDels can serve as ancestry informative markers to segregate global populations. This study provides a valuable resource for baseline Alu InDels that would be useful in population genomics.
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Affiliation(s)
- P Prakrithi
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
| | - Khushboo Singhal
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Disha Sharma
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Abhinav Jain
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Rahul C Bhoyar
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
| | - Mohamed Imran
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Vigneshwar Senthilvel
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Mohit Kumar Divakar
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Anushree Mishra
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
| | - Vinod Scaria
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Sridhar Sivasubbu
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - Mitali Mukerji
- CSIR Institute of Genomics and Integrative Biology, Mathura Road, New Delhi 110025, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
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5
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Kishita Y, Shimura M, Kohda M, Fushimi T, Nitta KR, Yatsuka Y, Hirose S, Ideguchi H, Ohtake A, Murayama K, Okazaki Y. Genome sequencing and RNA-seq analyses of mitochondrial complex I deficiency revealed Alu insertion-mediated deletion in NDUFV2. Hum Mutat 2021; 42:1422-1428. [PMID: 34405929 DOI: 10.1002/humu.24274] [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: 03/02/2021] [Revised: 06/25/2021] [Accepted: 07/15/2021] [Indexed: 11/08/2022]
Abstract
Isolated complex I deficiency is the most common cause of pediatric mitochondrial disease. Exome sequencing (ES) has revealed many complex I causative genes. However, there are limitations associated with identifying causative genes by ES analysis. In this study, we performed multiomics analysis to reveal the causal variants. We here report two cases with mitochondrial complex I deficiency. In both cases, ES identified a novel c.580G>A (p.Glu194Lys) variant in NDUFV2. One case additionally harbored c.427C>T (p.Arg143*), but no other variants were observed in the other case. RNA sequencing showed aberrant exon splicing of NDUFV2 in the unsolved case. Genome sequencing revealed a novel heterozygous deletion in NDUFV2, which included one exon and resulted in exon skipping. Detailed examination of the breakpoint revealed that an Alu insertion-mediated rearrangement caused the deletion. Our report reveals that combined use of transcriptome sequencing and GS was effective for diagnosing cases that were unresolved by ES.
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Affiliation(s)
- Yoshihito Kishita
- Diagnostics and Therapeutics of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan.,Department of Life Science, Faculty of Science and Engineering, Kindai University, Osaka, Japan
| | - Masaru Shimura
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
| | - Masakazu Kohda
- Diagnostics and Therapeutics of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan
| | - Takuya Fushimi
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
| | - Kazuhiro R Nitta
- Diagnostics and Therapeutics of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan
| | - Yukiko Yatsuka
- Diagnostics and Therapeutics of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan
| | - Shinichi Hirose
- General Medical Research Center, School of Medicine, Fukuoka University, Fukuoka, Japan
| | - Hiroshi Ideguchi
- Department of Pediatrics, Fukuoka Sanno Hospital, Fukuoka, Japan
| | - Akira Ohtake
- Department of Pediatrics & Clinical Genomics, Faculty of Medicine, Saitama Medical University, Saitama, Japan.,Center for Intractable Diseases, Saitama Medical University Hospital, Saitama, Japan
| | - Kei Murayama
- Diagnostics and Therapeutics of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan.,Department of Metabolism, Chiba Children's Hospital, Chiba, Japan.,Center for Medical Genetics, Chiba Children's Hospital, Chiba, Japan
| | - Yasushi Okazaki
- Diagnostics and Therapeutics of Intractable Diseases, Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo, Japan.,Laboratory for Comprehensive Genomic Analysis, RIKEN Centre for Integrative Medical Sciences, Kanagawa, Japan
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6
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Shi M, Chen X, Zeng L, Li Z, Liang D, Wu L. The rare Alus element-mediated chimerism of multiple de novo complex rearrangement sequences in GAN result in giant axonal neuropathy. Clin Chim Acta 2019; 502:91-98. [PMID: 31877298 DOI: 10.1016/j.cca.2019.12.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/16/2019] [Accepted: 12/20/2019] [Indexed: 02/02/2023]
Abstract
Giant axonal neuropathy (GAN) is a rare and grievous autosomal recessive neurodegenerative disease due to loss-of-function mutation in GAN. However, the chimerism of complex rearrangement sequences of GAN has not been reported so far, and the mechanism for its complex rearrangements remains to be determined. We identified a family with clinical symptoms of GAN and aimed to reveal a genetic cause underlying this disease. By whole-exome sequencing in the patient we identified a novel homozygous frameshift mutation with 1 bp deletion (c.27delC) in GAN. However, when analyzed the patient's genomic DNA (gDNA) by quantitative real-time PCR and breakpoint DNA sequencing, we found the chimerism of multiple complex rearrangement sequences encompassing exon 1 of GAN in the patient's genome. The microhomology and localization of the breakpoint indicated that they may be caused by Alu repeat elements. We also found that the mRNA expression level of GAN in patient's lymphocyte was decreased, confirming the pathogenicity of these mutations. Our study is the first reported on many complex rearrangement sequences mosaic in GAN mediated by Alu element. The patient here is not a simple homozygous frameshift mutation, but a compound heterozygous paternal c.27delC mutation and the chimerism of multiple de novo complex rearrangement sequences in GAN. Our results may also provide new insights into the formation and pathogenicity of complex rearrangement in GAN, and may be helpful to genetic counseling and genetic testing. It also enriches the Alu-mediated disease-associated database which are important for correct clinical interpretation.
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Affiliation(s)
- Meizhen Shi
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, PR China
| | - Xin Chen
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, PR China
| | - Lanlan Zeng
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, PR China
| | - Zhuo Li
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, PR China
| | - Desheng Liang
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, PR China.
| | - Lingqian Wu
- Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, 110 Xiangya Road, Changsha, Hunan 410078, PR China.
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8
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Krestel H, Meier JC. RNA Editing and Retrotransposons in Neurology. Front Mol Neurosci 2018; 11:163. [PMID: 29875629 PMCID: PMC5974252 DOI: 10.3389/fnmol.2018.00163] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 04/30/2018] [Indexed: 12/28/2022] Open
Abstract
Compared to sites in protein-coding sequences many more targets undergoing adenosine to inosine (A-to-I) RNA editing were discovered in non-coding regions of human cerebral transcripts, particularly in genetic transposable elements called retrotransposons. We review here the interaction mechanisms of RNA editing and retrotransposons and their impact on normal function and human neurological diseases. Exemplarily, A-to-I editing of retrotransposons embedded in protein-coding mRNAs can contribute to protein abundance and function via circular RNA formation, alternative splicing, and exonization or silencing of retrotransposons. Interactions leading to disease are not very well understood. We describe human diseases with involvement of the central nervous system including inborn errors of metabolism, neurodevelopmental disorders, neuroinflammatory and neurodegenerative and paroxysmal diseases, in which retrotransposons (Alu and/or L1 elements) appear to be causally involved in genetic rearrangements. Sole binding of single-stranded retrotransposon transcripts by RNA editing enzymes rather than enzymatic deamination may have a homeostatic effect on retrotransposon turnover. We also review evidence in support of the emerging pathophysiological function of A-to-I editing of retrotransposons in inflammation and its implication for different neurological diseases including amyotrophic lateral sclerosis, frontotemporal dementia, Alzheimer's and Parkinson's disease, and epilepsy.
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Affiliation(s)
- Heinz Krestel
- Department of Neurology, Bern University Hospital and University of Bern, Bern, Switzerland.,Department for BioMedical Research, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Jochen C Meier
- Division Cell Physiology, Zoological Institute, Technical University Braunschweig, Braunschweig, Germany
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9
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Jahic A, Hinreiner S, Emberger W, Hehr U, Zuchner S, Beetz C. Doublet-Mediated DNA Rearrangement-A Novel and Potentially Underestimated Mechanism for the Formation of Recurrent Pathogenic Deletions. Hum Mutat 2016; 38:275-278. [PMID: 28008689 DOI: 10.1002/humu.23162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 12/02/2016] [Accepted: 12/14/2016] [Indexed: 11/09/2022]
Abstract
Deletions and duplications of genomic DNA contribute to evolution, phenotypic diversity, and human disease. The underlying mechanisms are incompletely understood. We identified deletions of exon 10 of the SPAST gene in two unrelated families with hereditary spastic paraplegia. We excluded a founder event, but observed that the breakpoints map to identical repeat regions. These regions likely represent an intragenic "doublet," that is, an enigmatic class of local duplications. The fusion sequences for both deletions are compatible with recombination-based as well as with replication-based mechanisms. Searching the literature, we identified a partial SLC24A4 deletion that involved two copies of another doublet, and was likely formed in an analogous way. Comparing the SPAST and the SLC24A4 doublets with doublets identified previously suggested that many additional doublets have a high potential for triggering rearrangements. Considering that doublets are still being formed in the human genome, and that they likely create high local instability, we suggest that a two-step mechanism consisting of doublet generation and subsequent doublet-mediated deletion/duplication may underlie certain copy-number changes for which other mechanisms are currently assumed. Further studies are necessary to delineate the significance of the thus-far understudied doublets for the formation of copy-number variation.
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Affiliation(s)
- Amir Jahic
- Department of Clinical Chemistry and Laboratory Medicine, Jena University Hospital, Jena, Germany
| | - Sophie Hinreiner
- Department of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Werner Emberger
- Department of Human Genetics, Graz Medical University, Graz, Austria
| | - Ute Hehr
- Department of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Stephan Zuchner
- John T. Macdonald Department of Human Genetics and John P. Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, Florida
| | - Christian Beetz
- Department of Clinical Chemistry and Laboratory Medicine, Jena University Hospital, Jena, Germany
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10
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Günther S, Elert-Dobkowska E, Soehn AS, Hinreiner S, Yoon G, Heller R, Hellenbroich Y, Hübner CA, Ray PN, Hehr U, Bauer P, Sulek A, Beetz C. High Frequency of Pathogenic Rearrangements in SPG11 and Extensive Contribution of Mutational Hotspots and Founder Alleles. Hum Mutat 2016; 37:703-9. [PMID: 27071356 DOI: 10.1002/humu.23000] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 03/11/2016] [Accepted: 03/29/2016] [Indexed: 12/27/2022]
Abstract
Biallelic loss-of-function mutations in SPG11 cause a wide spectrum of recessively inherited, neurodegenerative disorders including hereditary spastic paraplegia (HSP), amyotrophic lateral sclerosis, and Charcot-Marie-Tooth disease. By comprehensive screening of three large cohorts of HSP index patients, we identified 83 alleles with "small" mutations and 13 alleles that carry large genomic rearrangements. Including relevant data from previous studies, we estimate that copy number variants (CNVs) account for ∼19% of pathogenic SPG11 alleles. The breakpoints for all novel and some previously reported CNVs were determined by long-range PCR and sequencing. This revealed several Alu-associated recombination hotspots. We also found evidence for additional mutational mechanisms, including for a two-step event in which an Alu retrotransposition preceded the actual rearrangement. Apparently independent samples with identical breakpoints were analyzed by microsatellite PCRs. The resulting haplotypes suggested the existence of two rearrangement founder alleles. Our findings widen the spectra of mutations and mutational mechanisms in SPG11, underscore the pivotal role played by Alus, and are of high diagnostic relevance for a wide spectrum of clinical phenotypes including the most frequent form of recessive HSP.
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Affiliation(s)
- Sven Günther
- Department of Clinical Chemistry and Laboratory Medicine, Jena University Hospital, Jena, Germany
| | | | - Anne S Soehn
- Institute of Medical Genetics and Applied Genomics, University Hospital of Tuebingen, Tuebingen, Germany
| | - Sophie Hinreiner
- Center for Human Genetics, and Department of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Grace Yoon
- Division of Clinical and Metabolic Genetics, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada
| | - Raoul Heller
- Institute of Human Genetics, University Hospital of Cologne, Cologne, Germany
| | | | | | - Peter N Ray
- Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Ute Hehr
- Center for Human Genetics, and Department of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Peter Bauer
- Institute of Medical Genetics and Applied Genomics, University Hospital of Tuebingen, Tuebingen, Germany
| | - Anna Sulek
- Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Christian Beetz
- Department of Clinical Chemistry and Laboratory Medicine, Jena University Hospital, Jena, Germany
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