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Loss of junctophilin‐3 contributes to huntington disease‐like 2 pathogenesis
Author(s) -
Seixas Ana I.,
Holmes Susan E.,
Takeshima Hiroshi,
Pavlovich Amira,
Sachs Nancy,
Pruitt Jennifer L.,
Silveira Isabel,
Ross Christopher A.,
Margolis Russell L.,
Rudnicki Dobrila D.
Publication year - 2012
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.22598
Subject(s) - pathogenesis , biology , huntington's disease , exon , trinucleotide repeat expansion , loss function , genetics , locus (genetics) , gene , disease , allele , medicine , phenotype , immunology
Abstract Objective: Huntington disease‐like 2 (HDL2) is a progressive, late onset autosomal dominant neurodegenerative disorder, with remarkable similarities to Huntington disease (HD). HDL2 is caused by a CTG/CAG repeat expansion. In the CTG orientation, the repeat is located within the alternatively spliced exon 2A of junctophilin‐3 ( JPH3 ), potentially encoding polyleucine and polyalanine, whereas on the strand antisense to JPH3 , the repeat is in frame to encode polyglutamine. The JPH3 protein product serves to stabilize junctional membrane complexes and regulate neuronal calcium flux. We have previously demonstrated the potential pathogenic properties of JPH3 transcripts containing expanded CUG repeats. The aim of this study was to test the possibility that loss of JPH3 expression or expanded amino acid tracts also contribute to HDL2 pathogenesis. Methods: Transcripts from the HDL2 locus, and their protein products, were examined in HDL2, HD, and control frontal cortex. The effect of loss of Jph3 was examined in mice with partial or complete loss of Jph3 . Results: Bidirectional transcription occurs at the HDL2 locus, although expression of antisense transcripts with expanded CAG repeats is limited. Protein products with expanded amino acid tracts were not detected in HDL2 brain. However, JPH3 transcripts and full‐length JPH3 protein are decreased in HDL2 brain, and Jph3 hemizygous and null mice exhibit abnormal motor function. Interpretation: Our results suggest that the pathogenic mechanism of HDL2 is multifactorial, involving both a toxic gain of function of JPH3 RNA and a toxic loss of JPH3 expression. Ann Neurol 2012;71:245–257