High-throughput mutational analysis of TOR1A in primary dystonia

Jianfeng Xiao,Andrew Blitzer,Yu Zhao,Daniel Tarsy,Sat Dev Batish,Peter Hedera,Morvarid Karimi,Shusheng Gong ,Samer D Tabbal ,Ronald F Pfeiffer ,Zbigniew K Wszołek ,Karen Frei ,Ryan J Uitti ,Brad A Racette ,David K Simon ,Daniel Truong ,Joel S Perlmutter ,Randal C Paniello ,Robert W Bastian ,Mark S Ledoux

doi:10.1186/1471-2350-10-24

Abstract

BackgroundAlthough the c.904_906delGAG mutation in Exon 5 of TOR1A typically manifests as early-onset generalized dystonia, DYT1 dystonia is genetically and clinically heterogeneous. Recently, another Exon 5 mutation (c.863G>A) has been associated with early-onset generalized dystonia and some ΔGAG mutation carriers present with late-onset focal dystonia. The aim of this study was to identify TOR1A Exon 5 mutations in a large cohort of subjects with mainly non-generalized primary dystonia.MethodsHigh resolution melting (HRM) was used to examine the entire TOR1A Exon 5 coding sequence in 1014 subjects with primary dystonia (422 spasmodic dysphonia, 285 cervical dystonia, 67 blepharospasm, 41 writer's cramp, 16 oromandibular dystonia, 38 other primary focal dystonia, 112 segmental dystonia, 16 multifocal dystonia, and 17 generalized dystonia) and 250 controls (150 neurologically normal and 100 with other movement disorders). Diagnostic sensitivity and specificity were evaluated in an additional 8 subjects with known ΔGAG DYT1 dystonia and 88 subjects with ΔGAG-negative dystonia.ResultsHRM of TOR1A Exon 5 showed high (100%) diagnostic sensitivity and specificity. HRM was rapid and economical. HRM reliably differentiated the TOR1A ΔGAG and c.863G>A mutations. Melting curves were normal in 250/250 controls and 1012/1014 subjects with primary dystonia. The two subjects with shifted melting curves were found to harbor the classic ΔGAG deletion: 1) a non-Jewish Caucasian female with childhood-onset multifocal dystonia and 2) an Ashkenazi Jewish female with adolescent-onset spasmodic dysphonia.ConclusionFirst, HRM is an inexpensive, diagnostically sensitive and specific, high-throughput method for mutation discovery. Second, Exon 5 mutations in TOR1A are rarely associated with non-generalized primary dystonia.

Highlights

The c.904_906delGAG mutation in Exon 5 of TOR1A typically manifests as early-onset generalized dystonia, DYT1 dystonia is genetically and clinically heterogeneous
Genetic factors likely play a major role in late-onset primary dystonia since 8–27% of patients with primary late-onset dystonia have one or more family members affected with dystonia [5,6,7,8,9] and several of the primary dystonias inherited in Mendelian fashion (DYT1, DYT5, DYT6, DYT11, and DYT12) begin focally, show incomplete penetrance and exhibit variable anatomical expressivity [10,11,12]
Our results indicate that mutations in Exon 5 of TOR1A are rare in non-generalized primary dystonia

Summary

Introduction

The c.904_906delGAG mutation in Exon 5 of TOR1A typically manifests as early-onset generalized dystonia, DYT1 dystonia is genetically and clinically heterogeneous. Genetic factors likely play a major role in late-onset primary dystonia since 8–27% of patients with primary late-onset dystonia have one or more family members affected with dystonia [5,6,7,8,9] and several of the primary dystonias inherited in Mendelian fashion (DYT1, DYT5, DYT6, DYT11, and DYT12) begin focally, show incomplete penetrance and exhibit variable anatomical expressivity [10,11,12] These facts suggest that sporadic late-onset dystonia, much like Parkinson's disease, is a complex disorder with contributions from multiple genes and environmental factors. Late-onset sporadic dystonia could be associated with a number of distinct mutations of low penetrance

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