1. Biallelic variants in LIG3 cause a novel mitochondrial neurogastrointestinal encephalomyopathy.
- Author
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Bonora E, Chakrabarty S, Kellaris G, Tsutsumi M, Bianco F, Bergamini C, Ullah F, Isidori F, Liparulo I, Diquigiovanni C, Masin L, Rizzardi N, Cratere MG, Boschetti E, Papa V, Maresca A, Cenacchi G, Casadio R, Martelli P, Matera I, Ceccherini I, Fato R, Raiola G, Arrigo S, Signa S, Sementa AR, Severino M, Striano P, Fiorillo C, Goto T, Uchino S, Oyazato Y, Nakamura H, Mishra SK, Yeh YS, Kato T, Nozu K, Tanboon J, Morioka I, Nishino I, Toda T, Goto YI, Ohtake A, Kosaki K, Yamaguchi Y, Nonaka I, Iijima K, Mimaki M, Kurahashi H, Raams A, MacInnes A, Alders M, Engelen M, Linthorst G, de Koning T, den Dunnen W, Dijkstra G, van Spaendonck K, van Gent DC, Aronica EM, Picco P, Carelli V, Seri M, Katsanis N, Duijkers FAM, Taniguchi-Ikeda M, and De Giorgio R
- Subjects
- Animals, Female, Gastrointestinal Diseases pathology, Humans, Male, Mitochondrial Encephalomyopathies pathology, Mutation, Pedigree, Zebrafish, DNA Ligase ATP genetics, Gastrointestinal Diseases genetics, Gastrointestinal Motility genetics, Mitochondrial Encephalomyopathies genetics, Poly-ADP-Ribose Binding Proteins genetics
- Abstract
Abnormal gut motility is a feature of several mitochondrial encephalomyopathies, and mutations in genes such as TYMP and POLG, have been linked to these rare diseases. The human genome encodes three DNA ligases, of which only one, ligase III (LIG3), has a mitochondrial splice variant and is crucial for mitochondrial health. We investigated the effect of reduced LIG3 activity and resulting mitochondrial dysfunction in seven patients from three independent families, who showed the common occurrence of gut dysmotility and neurological manifestations reminiscent of mitochondrial neurogastrointestinal encephalomyopathy. DNA from these patients was subjected to whole exome sequencing. In all patients, compound heterozygous variants in a new disease gene, LIG3, were identified. All variants were predicted to have a damaging effect on the protein. The LIG3 gene encodes the only mitochondrial DNA (mtDNA) ligase and therefore plays a pivotal role in mtDNA repair and replication. In vitro assays in patient-derived cells showed a decrease in LIG3 protein levels and ligase activity. We demonstrated that the LIG3 gene defects affect mtDNA maintenance, leading to mtDNA depletion without the accumulation of multiple deletions as observed in other mitochondrial disorders. This mitochondrial dysfunction is likely to cause the phenotypes observed in these patients. The most prominent and consistent clinical signs were severe gut dysmotility and neurological abnormalities, including leukoencephalopathy, epilepsy, migraine, stroke-like episodes, and neurogenic bladder. A decrease in the number of myenteric neurons, and increased fibrosis and elastin levels were the most prominent changes in the gut. Cytochrome c oxidase (COX) deficient fibres in skeletal muscle were also observed. Disruption of lig3 in zebrafish reproduced the brain alterations and impaired gut transit in vivo. In conclusion, we identified variants in the LIG3 gene that result in a mitochondrial disease characterized by predominant gut dysmotility, encephalopathy, and neuromuscular abnormalities., (© The Author(s) (2021). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For permissions, please email: journals.permissions@oup.com.)
- Published
- 2021
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