Confirming TDP2 mutation in spinocerebellar ataxia autosomal recessive 23 (SCAR23)
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Abstract
Objective To address the relationship between mutations in the DNA strand break repair protein tyrosyl DNA phosphodiesterase 2 (TDP2) and spinocerebellar ataxia autosomal recessive 23 (SCAR23) and to characterize the cellular phenotype of primary fibroblasts from this disease.
Methods We have used exome sequencing, Sanger sequencing, gene editing and cell biology, biochemistry, and subcellular mitochondrial analyses for this study.
Results We have identified a patient in the United States with SCAR23 harboring the same homozygous TDP2 mutation as previously reported in 3 Irish siblings (c.425+1G>A). The current and Irish patients share the same disease haplotype, but the current patient lacks a homozygous variant present in the Irish siblings in the closely linked gene ZNF193, eliminating this as a contributor to the disease. The current patient also displays symptoms consistent with mitochondrial dysfunction, although levels of mitochondrial function in patient primary skin fibroblasts are normal. However, we demonstrate an inability in patient primary fibroblasts to rapidly repair topoisomerase-induced DNA double-strand breaks (DSBs) in the nucleus and profound hypersensitivity to this type of DNA damage.
Conclusions These data confirm the TDP2 mutation as causative for SCAR23 and highlight the link between defects in nuclear DNA DSB repair, developmental delay, epilepsy, and ataxia.
Glossary
- DSB=
- double-strand break;
- ETC=
- electron transport chain;
- FCS=
- fetal calf serum;
- NHEJ=
- nonhomologous end joining;
- SCAR23=
- spinocerebellar ataxia, autosomal recessive 23;
- TDP2=
- tyrosyl DNA phosphodiesterase 2;
- WCE=
- whole-cell extract;
- WES=
- Whole-exome sequencing
Footnotes
↵* Current address: Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy.
Funding information and disclosures are provided at the end of the article. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/NG.
The Article Processing Charge was funded by the authors.
- Received December 20, 2017.
- Accepted in final form May 24, 2018.
- Copyright © 2018 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.
This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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