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Ann Neurol. 2018 Jun;83(6):1075-1088. doi: 10.1002/ana.25220. Epub 2018 Jun 30.

Mutations in VPS13D lead to a new recessive ataxia with spasticity and mitochondrial defects.

Author information

1
Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, MI.
2
Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI.
3
Institute of Neurogenetics, University of Lübeck, Lübeck, Germany.
4
Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands.
5
Department of Neurology, University of Lübeck, Lübeck, Germany.
6
Department of Human Genetics, University of Michigan, Ann Arbor, MI.
7
Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI.
8
Department of Pediatrics, Section on Medical Genetics, Wake Forest School of Medicine, Winston-Salem, NC.
9
Department of Clinical Genetics, Erasmus MC, Rotterdam, the Netherlands.
10
Departments of Neurology and Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI.
11
Department of Neurology, Donders Institute for Brain, Cognition, and Behavior, Radboud University Medical Centre, Nijmegen, the Netherlands.
12
Department of Psychiatry, University of Michigan, Ann Arbor, MI.

Abstract

OBJECTIVE:

To identify novel causes of recessive ataxias, including spinocerebellar ataxia with saccadic intrusions, spastic ataxias, and spastic paraplegia.

METHODS:

In an international collaboration, we independently performed exome sequencing in 7 families with recessive ataxia and/or spastic paraplegia. To evaluate the role of VPS13D mutations, we evaluated a Drosophila knockout model and investigated mitochondrial function in patient-derived fibroblast cultures.

RESULTS:

Exome sequencing identified compound heterozygous mutations in VPS13D on chromosome 1p36 in all 7 families. This included a large family with 5 affected siblings with spinocerebellar ataxia with saccadic intrusions (SCASI), or spinocerebellar ataxia, recessive, type 4 (SCAR4). Linkage to chromosome 1p36 was found in this family with a logarithm of odds score of 3.1. The phenotypic spectrum in our 12 patients was broad. Although most presented with ataxia, additional or predominant spasticity was present in 5 patients. Disease onset ranged from infancy to 39 years, and symptoms were slowly progressive and included loss of independent ambulation in 5. All but 2 patients carried a loss-of-function (nonsense or splice site) mutation on one and a missense mutation on the other allele. Knockdown or removal of Vps13D in Drosophila neurons led to changes in mitochondrial morphology and impairment in mitochondrial distribution along axons. Patient fibroblasts showed altered morphology and functionality including reduced energy production.

INTERPRETATION:

Our study demonstrates that compound heterozygous mutations in VPS13D cause movement disorders along the ataxia-spasticity spectrum, making VPS13D the fourth VPS13 paralog involved in neurological disorders. Ann Neurol 2018.

PMID:
29604224
PMCID:
PMC6105379
[Available on 2019-06-30]
DOI:
10.1002/ana.25220

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