Development of a multiplex ligation-dependent probe amplification assay for diagnosis and estimation of the frequency of spinocerebellar ataxia type 15.
BACKGROUND
Spinocerebellar ataxia type 15 (SCA15) is a slowly progressive neurodegenerative disorder characterized by cerebellar ataxia. Mutation of the ITPR1 gene (inositol 1,4,5-triphosphate receptor, type 1) has been identified recently as the underlying cause, and in most cases the molecular defect is a multiexon deletion. To date, 5 different SCA15 families have been identified with ITPR1 gene deletion.


METHODS
We have designed a synthetic, dual-color multiplex ligation-dependent probe amplification (MLPA) assay that measures copy number with high precision in selected exons across the entire length of ITPR1 and the proximal region of the neighboring gene, SUMF1 (sulfatase modifying factor 1). We screened 189 idiopathic ataxic patients with this MLPA assay.


RESULTS
We identified ITPR1 deletion of exons 1-10 in the previously reported AUS1 family (4 members) and deletion of exons 1-38 in a new family (2 members). In addition to the multiexon deletions, apparent single-exon deletions identified in 2 other patients were subsequently shown to be due to single-nucleotide changes at the ligation sites.


CONCLUSIONS
The frequency of ITPR1 deletions is 2.7% in known familial cases. This finding suggests that SCA15 is one of the "less common" SCAs. Although the deletions in the 5 families identified worldwide thus far have been of differing sizes, all share deletion of exons 1-10. This region may be important, both in terms of the underlying pathogenetic mechanism and as a pragmatic target for an accurate, robust, and cost-effective diagnostic analysis.
Victorian Clinical Genetic Services and Murdoch Children's Research Institute, University of Melbourne, Department of Paediatrics, Royal Children's Hospital, Parkville, Victoria, Australia.
Devika
D
Ganesamoorthy
Damien L
DL
Bruno
Jacqueline
J
Schoumans
Elsdon
E
Storey
Martin B
MB
Delatycki
Danqing
D
Zhu
Morgan K
MK
Wei
Garth A
GA
Nicholson
R J
RJ
McKinlay Gardner
Howard R
HR
Slater
D001315:Australia / Q000453:epidemiology; D015342:DNA Probes; D005784:Gene Amplification; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics; D050862:Oxidoreductases Acting on Sulfur Group Donors; D017384:Sequence Deletion; D020754:Spinocerebellar Ataxias / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D013429:Sulfatases / Q000235:genetics
D015342:DNA Probes; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D050862:Oxidoreductases Acting on Sulfur Group Donors; C480483:SUMF1 protein, human; D013429:Sulfatases