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Shimojima Yamamoto K, Tamura T, Okamoto N, Nishi E, Noguchi A, Takahashi I, Sawaishi Y, Shimizu M, Kanno H, Minakuchi Y, Toyoda A, Yamamoto T. Identification of small-sized intrachromosomal segments at the ends of INV-DUP-DEL patterns. J Hum Genet 2023; 68:751-757. [PMID: 37423943 DOI: 10.1038/s10038-023-01181-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 06/14/2023] [Accepted: 06/27/2023] [Indexed: 07/11/2023]
Abstract
The mechanism of chromosomal rearrangement associated with inverted-duplication-deletion (INV-DUP-DEL) pattern formation has been investigated by many researchers, and several possible mechanisms have been proposed. Currently, fold-back and subsequent dicentric chromosome formation has been established as non-recurrent INV-DUP-DEL pattern formation mechanisms. In the present study, we analyzed the breakpoint junctions of INV-DUP-DEL patterns in five patients using long-read whole-genome sequencing and detected 2.2-6.1 kb copy-neutral regions in all five patients. At the end of the INV-DUP-DEL, two patients exhibited chromosomal translocations, which are recognized as telomere capture, and one patient showed direct telomere healing. The remaining two patients had additional small-sized intrachromosomal segments at the end of the derivative chromosomes. These findings have not been previously reported but they may only be explained by the presence of telomere capture breakage. Further investigations are required to better understand the mechanisms underlying this finding.
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Affiliation(s)
- Keiko Shimojima Yamamoto
- Department of Transfusion Medicine and Cell Processing, Tokyo Women's Medical University, Tokyo, 162-8666, Japan
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, 162-8666, Japan
| | - Takeaki Tamura
- Department of Pediatrics and Child Health, Nihon University School of Medicine, Tokyo, 173-8610, Japan
- Division of Gene Medicine, Graduate Scholl of Medical Science, Tokyo Women's Medical University, Tokyo, 162-8666, Japan
| | - Nobuhiko Okamoto
- Department of Medical Genetics, Osaka Women's and Children's Hospital, Izumi, 594-1101, Japan
| | - Eriko Nishi
- Department of Medical Genetics, Osaka Women's and Children's Hospital, Izumi, 594-1101, Japan
| | - Atsuko Noguchi
- Department of Pediatrics, Akita University Graduate School of Medicine, Akita, 010-8543, Japan
| | - Ikuko Takahashi
- Department of Pediatrics, Akita University Graduate School of Medicine, Akita, 010-8543, Japan
| | - Yukio Sawaishi
- Department of Pediatrics, Akita Prefectural Center on Development and Disability, Akita, 010-0000, Japan
| | - Masaki Shimizu
- Department of Pediatrics and Developmental Biology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, 113-8519, Japan
| | - Hitoshi Kanno
- Department of Transfusion Medicine and Cell Processing, Tokyo Women's Medical University, Tokyo, 162-8666, Japan
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, 162-8666, Japan
| | - Yohei Minakuchi
- Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima, Shizuoka, 411-0801, Japan
| | - Atsushi Toyoda
- Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima, Shizuoka, 411-0801, Japan
| | - Toshiyuki Yamamoto
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, 162-8666, Japan.
- Division of Gene Medicine, Graduate Scholl of Medical Science, Tokyo Women's Medical University, Tokyo, 162-8666, Japan.
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Genomic Aberrations Associated with the Pathophysiological Mechanisms of Neurodevelopmental Disorders. Cells 2021; 10:cells10092317. [PMID: 34571966 PMCID: PMC8470284 DOI: 10.3390/cells10092317] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 08/30/2021] [Accepted: 09/03/2021] [Indexed: 12/27/2022] Open
Abstract
Genomic studies are increasingly revealing that neurodevelopmental disorders are caused by underlying genomic alterations. Chromosomal microarray testing has been used to reliably detect minute changes in genomic copy numbers. The genes located in the aberrated regions identified in patients with neurodevelopmental disorders may be associated with the phenotypic features. In such cases, haploinsufficiency is considered to be the mechanism, when the deletion of a gene is related to neurodevelopmental delay. The loss-of-function mutation in such genes may be evaluated using next-generation sequencing. On the other hand, the patients with increased copy numbers of the genes may exhibit different clinical symptoms compared to those with loss-of-function mutation in the genes. In such cases, the additional copies of the genes are considered to have a dominant negative effect, inducing cell stress. In other cases, not the copy number changes, but mutations of the genes are responsible for causing the clinical symptoms. This can be explained by the dominant negative effects of the gene mutations. Currently, the diagnostic yield of genomic alterations using comprehensive analysis is less than 50%, indicating the existence of more subtle alterations or genomic changes in the untranslated regions. Copy-neutral inversions and insertions may be related. Hence, better analytical algorithms specialized for the detection of such alterations are required for higher diagnostic yields.
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