Spinocerebellar ataxia type 17 mutation as a causative and susceptibility gene in parkinsonism.
OBJECTIVE
To investigate the role of spinocerebellar ataxia type 17 (SCA17) in the development of parkinsonism.


METHODS
We screened 1,155 parkinsonian patients (931 with Parkinson disease and 224 with multiple system atrophy) and 400 normal subjects for SCA17. 99mTc-TRODAT-1 SPECT was used to evaluate the striatal dopamine transporter (DAT) status.


RESULTS
Trinucleotide expansion in the SCA17 gene was found in 10 parkinsonian patients (8 with Parkinson disease, 2 with multiple system atrophy) using 42 repeats as an upper normal limit. The repeat sizes in the patients ranged from 43 to 46, which are considered to be low-range expansions. All patients had interrupted sequences. Three probands and three asymptomatic carriers underwent 99mTc-TRODAT-1 SPECT. Striatal DAT binding was markedly reduced in all probands and mildly decreased in one asymptomatic carrier. Among the 400 normal control subjects, there was one individual with an expansion of 44 repeats, another with 43 repeats, and two with 42 repeats. Striatal DAT binding was decreased not only in the control subjects with 44 or 43 repeats, but in ones with 42 repeats, suggesting that an expansion as low as 42 repeats might constitute a susceptibility gene for parkinsonism.


CONCLUSIONS
Low-range expansion of the SCA17 gene is not a rare genetic cause of parkinsonism without ataxia in our population. Reduced penetrance or variable expressivity in low-range expansion might be an explanation for the blurred cutoff point for normal expansion in SCA17.
Kim
J-Y
JY
Department of Neurology, Neuroscience Research Institute, Korea.
Kim
S Y
SY
Kim
J-M
JM
Kim
Y K
YK
Yoon
K-Y
KY
Kim
J Y
JY
Lee
B C
BC
Kim
J S
JS
Paek
S H
SH
Park
S S
SS
Kim
S E
SE
Jeon
B S
BS
D000368:Aged; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology; D004252:DNA Mutational Analysis; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005820:Genetic Testing; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000000981:diagnostic imaging / Q000235:genetics / Q000503:physiopathology; D009154:Mutation / Q000235:genetics*; D015609:Organotechnetium Compounds; D020734:Parkinsonian Disorders / Q000000981:diagnostic imaging / Q000235:genetics* / Q000503:physiopathology; D011237:Predictive Value of Tests; D013378:Substantia Nigra / Q000378:metabolism / Q000503:physiopathology; D035181:TATA-Box Binding Protein / Q000235:genetics*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014326:Tropanes
D015415:Biomarkers; D050483:Dopamine Plasma Membrane Transport Proteins; D015609:Organotechnetium Compounds; D035181:TATA-Box Binding Protein; C509817:TBP protein, human; D014326:Tropanes; C104196:technetium Tc 99m TRODAT-1