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Open Access Research article

Exome sequencing reveals a novel TTC19 mutation in an autosomal recessive spinocerebellar ataxia patient

Hiroyuki Morino1*, Ryosuke Miyamoto1, Shizuo Ohnishi2, Hirofumi Maruyama1 and Hideshi Kawakami1

Author Affiliations

1 Department of Epidemiology, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Hiroshima 734-8553, Japan

2 Department of Neurology, Tanabe Neurological Hospital, Fujiidera, Osaka, Japan

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BMC Neurology 2014, 14:5  doi:10.1186/1471-2377-14-5

Published: 7 January 2014

Abstract

Background

Spinocerebellar ataxias (SCAs) are heterogeneous diseases characterized by progressive cerebellar ataxia associated with dysarthria, oculomotor abnormalities, and mental impairment. To identify the causative gene, we performed exome sequencing on a Japanese patient clinically diagnosed with recessive SCA.

Method

The patient is a 37-year-old Japanese woman with consanguineous parents. The head magnetic resonance imaging (MRI) showed cerebellar atrophy and T1 low/T2 high intensity at the bilateral inferior olives. Single-nucleotide polymorphism (SNP) genotyping and next-generation sequencing were performed, and the variants obtained were filtered and prioritized.

Results

After these manipulations, we identified a homozygous nonsense mutation of the TTC19 gene (p.Q277*). TTC19 has been reported to be a causative gene of a neurodegenerative disease in Italian and Portuguese families and to be involved in the pathogenesis of mitochondrial respiratory chain complex III (cIII) deficiency. This report is the first description of a TTC19 mutation in an Asian population. Clinical symptoms and neuroimaging are consistent with previous reports. The head MRI already showed abnormal features four years before her blood lactate and pyruvate levels were elevated.

Conclusions

We should consider the genetic analysis of TTC19 when we observe such characteristic MRI abnormalities. Genes associated with mitochondrial function cause many types of SCAs; the mutation we identified should help to elucidate the pathology of these disorders.

Keywords:
Exome sequencing; Mitochondrial respiratory chain complex III; Nonsense mutation; Spinocerebellar ataxia; TTC19