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An atypical form of AOA2 with myoclonus associated with mutations in SETX and AFG3L2.

Authors :
Cecilia Mancini
Laura Orsi
Yiran Guo
Jiankang Li
Yulan Chen
Fengxiang Wang
Lifeng Tian
Xuanzhu Liu
Jianguo Zhang
Hui Jiang
Bruce Shike Nmezi
Takashi Tatsuta
Giorgio, Elisa
Di Gregorio, Eleonora
Cavalieri, Simona
Pozzi, Elisa
Mortara, Paolo
Caglio, Maria Marcella
Balducci, Alessandro
Pinessi, Lorenzo
Source :
BMC Medical Genetics; 2015, Vol. 16 Issue 1, p1-7, 7p
Publication Year :
2015

Abstract

Background: Hereditary ataxias are a heterogeneous group of neurodegenerative disorders, where exome sequencing may become an important diagnostic tool to solve clinically or genetically complex cases. Methods: We describe an Italian family in which three sisters were affected by ataxia with postural/intentional myoclonus and involuntary movements at onset, which persisted during the disease. Oculomotor apraxia was absent. Clinical and genetic data did not allow us to exclude autosomal dominant or recessive inheritance and suggest a disease gene. Results: Exome sequencing identified a homozygous c.6292C > T (p.Arg2098*) mutation in SETX and a heterozygous c.346G > A (p.Gly116Arg) mutation in AFG3L2 shared by all three affected individuals. A fourth sister (II.7) had subclinical myoclonic jerks at proximal upper limbs and perioral district, confirmed by electrophysiology, and carried the p.Gly116Arg change. Three siblings were healthy. Pathogenicity prediction and a yeast-functional assay suggested p.Gly116Arg impaired m-AAA (ATPases associated with various cellular activities) complex function. Conclusions: Exome sequencing is a powerful tool in identifying disease genes. We identified an atypical form of Ataxia with Oculoapraxia type 2 (AOA2) with myoclonus at onset associated with the c.6292C > T (p.Arg2098*) homozygous mutation. Because the same genotype was described in six cases from a Tunisian family with a typical AOA2 without myoclonus, we speculate this latter feature is associated with a second mutated gene, namely AFG3L2 (p.Gly116Arg variant). We suggest that variant phenotypes may be due to the combined effect of different mutated genes associated to ataxia or related disorders, that will become more apparent as the costs of exome sequencing progressively will reduce, amplifying its diagnostics use, and meanwhile proposing significant challenges in the interpretation of the data. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
14712350
Volume :
16
Issue :
1
Database :
Complementary Index
Journal :
BMC Medical Genetics
Publication Type :
Academic Journal
Accession number :
101990940
Full Text :
https://doi.org/10.1186/s12881-015-0159-0