A pathogenic proteolysis–resistant huntingtin isoform induced by an antisense oligonucleotide maintains huntingtin function
Hyeongju Kim, Sophie Lenoir, Angela Helfricht, Taeyang Jung, Zhana K. Karneva, Yejin Lee, Wouter Beumer, Geert B. van der Horst, Herma Anthonijsz, Levi C.M. Buil, Frits van der Ham, Gerard J. Platenburg, Pasi Purhonen, Hans Hebert, Sandrine Humbert, Frédéric Saudou, Pontus Klein, Ji-Joon Song
Hyeongju Kim, Sophie Lenoir, Angela Helfricht, Taeyang Jung, Zhana K. Karneva, Yejin Lee, Wouter Beumer, Geert B. van der Horst, Herma Anthonijsz, Levi C.M. Buil, Frits van der Ham, Gerard J. Platenburg, Pasi Purhonen, Hans Hebert, Sandrine Humbert, Frédéric Saudou, Pontus Klein, Ji-Joon Song
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Research Article Neuroscience

A pathogenic proteolysis–resistant huntingtin isoform induced by an antisense oligonucleotide maintains huntingtin function

Abstract

Huntington’s disease (HD) is a late-onset neurological disorder for which therapeutics are not available. Its key pathological mechanism involves the proteolysis of polyglutamine-expanded (polyQ-expanded) mutant huntingtin (mHTT), which generates N-terminal fragments containing polyQ, a key contributor to HD pathogenesis. Interestingly, a naturally occurring spliced form of HTT mRNA with truncated exon 12 encodes an HTT (HTTΔ12) with a deletion near the caspase-6 cleavage site. In this study, we used a multidisciplinary approach to characterize the therapeutic potential of targeting HTT exon 12. We show that HTTΔ12 was resistant to caspase-6 cleavage in both cell-free and tissue lysate assays. However, HTTΔ12 retained overall biochemical and structural properties similar to those of wt-HTT. We generated mice in which HTT exon 12 was truncated and found that the canonical exon 12 was dispensable for the main physiological functions of HTT, including embryonic development and intracellular trafficking. Finally, we pharmacologically induced HTTΔ12 using the antisense oligonucleotide (ASO) QRX-704. QRX-704 showed predictable pharmacology and efficient biodistribution. In addition, it was stable for several months and inhibited pathogenic proteolysis. Furthermore, QRX-704 treatments resulted in a reduction of HTT aggregation and an increase in dendritic spine count. Thus, ASO-induced HTT exon 12 splice switching from HTT may provide an alternative therapeutic strategy for HD.

Authors

Hyeongju Kim, Sophie Lenoir, Angela Helfricht, Taeyang Jung, Zhana K. Karneva, Yejin Lee, Wouter Beumer, Geert B. van der Horst, Herma Anthonijsz, Levi C.M. Buil, Frits van der Ham, Gerard J. Platenburg, Pasi Purhonen, Hans Hebert, Sandrine Humbert, Frédéric Saudou, Pontus Klein, Ji-Joon Song

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Figure 6

HTTΔ12 does not influence cilia assembly.

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HTTΔ12 does not influence cilia assembly. (A) Representative images of p...
(A) Representative images of primary cilia (Arl13b immunostaining) induced by serum starvation in fibroblasts transfected with ASO or Scrb. (Arrows indicate cells with primary cilia and stars indicate cells without cilia. Scale bars: 10 μm and 5 μm for higher magnification.) (B) Bar graphs show the percentage of cells with primary cilia in control (Scrb) or HTT-depleted (ASO) fibroblasts. Results were obtained from 7 cultures from 4 independent experiments in which n = 59 regions of interest (ROI) were analyzed. D’Agostino-Pearson normality test followed by unpaired 2-tailed Student’s t test: *P < 0.05. (C) Representative images of primary cilia (Arl13b immunostaining) of HTT or HTTΔ12 fibroblasts. (Arrows indicate cells with primary cilia and stars indicate cells without cilia. Scale bars: 10 μm and 5 μm for higher magnification.) (D) Bar graphs show the percentage of cells with primary cilia in HTT and HTTΔ12 fibroblasts. Results were obtained from 6–8 cultures from 3 independent experiments in which n = 46 HTT and n = 62 HTTΔ12 ROI were analyzed (Supplemental Data 1). D’Agostino-Pearson normality test followed by unpaired 2-tailed Student’s t test.