Biallelic GGGCC repeat expansion leading to NAXE-related mitochondrial encephalopathy
Abstract Repeat expansions cause at least 50 hereditary disorders, including Friedreich ataxia and other diseases known to cause mitochondrial dysfunction. We identified a patient with NAXE-related mitochondrial encephalopathy and novel biallelic GGGCC repeat expansion as long as ~200 repeats in the...
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| Main Authors: | , , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2024-10-01
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| Series: | npj Genomic Medicine |
| Online Access: | https://doi.org/10.1038/s41525-024-00429-5 |
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| Summary: | Abstract Repeat expansions cause at least 50 hereditary disorders, including Friedreich ataxia and other diseases known to cause mitochondrial dysfunction. We identified a patient with NAXE-related mitochondrial encephalopathy and novel biallelic GGGCC repeat expansion as long as ~200 repeats in the NAXE promoter region using long-read sequencing. In addition to a marked reduction in the RNA and protein, we found a marked reduction in nascent RNA in the promoter using native elongating transcript-cap analysis of gene expression (NET-CAGE), suggesting transcriptional suppression. Accordingly, CpG hypermethylation was observed in the repeat region. Genetic analyses determined that homozygosity in the patient was due to maternal chromosome 1 uniparental disomy (UPD). We assessed short variants within NAXE including the repeat region in the undiagnosed mitochondrial encephalopathy cohort of 242 patients. This study identified the GGGCC repeat expansion causing a mitochondrial disease and suggests that UPD could significantly contribute to homozygosity for rare repeat-expanded alleles. |
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| ISSN: | 2056-7944 |