Abstract
The most common known cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is a hexanucleotide repeat expansion (HRE) in C9ORF72 that contributes to neurodegeneration by both loss-of-function (decreased C9ORF72 protein levels) and gain-of-function (e.g. dipeptide repeat protein production) mechanisms. Although therapeutics targeting the gain-of-function mechanisms are in clinical development, it is unclear if these will be efficacious given the contribution of C9ORF72 loss-of-function processes to neurodegeneration. Moreover, there is a lack of therapeutic strategies for C9ORF72 ALS/FTD with demonstrated efficacy in vivo. Here, we show that small molecule inhibition of PIKFYVE kinase rescues both loss- and gain-of-function C9ORF72 disease mechanisms in vivo. We find that the reduction of C9ORF72 in mouse motor neurons leads to a decrease in early endosomes. In contrast, treatment with the PIKFYVE inhibitor apilimod increases the number of endosomes and lysosomes. We show that reduced C9ORF72 levels increases glutamate receptor levels in hippocampal neurons in mice, and that apilimod treatment rescues this excitotoxicity-related phenotype in vivo. Finally, we show that apilimod also alleviates the gain-of-function pathology induced by the C9ORF72 HRE by decreasing levels of dipeptide repeat proteins derived from both sense and antisense C9ORF72 transcripts in hippocampal neurons in vivo. Our data demonstrate the neuroprotective effect of PIKFYVE kinase inhibition in both gain- and loss-of-function murine models of C9ORF72 ALS/FTD.
Footnotes
Staats, K. A. Kim.Staats.Work{at}gmail.com, Seah C. cseah{at}usc.edu, Sahimi, A. asahimi{at}usc.edu, Wang, Y. yaomingw{at}usc.edu, Koutsodendris, N. nkoutsodendris{at}gmail.com, Lin, S. shaoyuli{at}usc.edu, Kim, D. david.k.2015{at}gmail.com, Chang, W-H. wchang{at}acurastem.com, Gray, K. A. kag262{at}georgetown.edu, Shi, Y. shiyingxiao{at}gmail.com, Li, Y. yichen.li{at}st-annes.ox.ac.uk, Chateau, M. mchateau{at}usc.edu, Vangoor, V. R. V.Vangoor{at}umcutrecht.nl, Senthilkumar, K. K.Senthilkumar-2{at}umcutrecht.nl, Pasterkamp, R. J. R.J.Pasterkamp{at}umcutrecht.nl, Cannon, P. PCannon{at}usc.edu, Zlokovic, B.V. Zlokovic{at}usc.edu, Ichida, J. K. Ichida{at}usc.edu
List of abbreviations
- ALS
- amyotrophic lateral sclerosis
- CA
- Cornu Ammonis
- C9-ALS/FTD
- C9orf72 ALS/FTD
- C9-BAC mice
- C9orf72 containing 100-1000 GGGGCC repeats mice
- DG
- dentate gyrus
- DPR
- dipeptide repeat protein
- EEA1
- Early Endosome Antigen 1
- FTD
- frontotemporal dementia
- GP
- glycine-proline repeat DPR
- GR
- glycine-arginine repeat DPR
- HRE
- hexanucleotide repeat expansion
- HRP
- horseradish peroxidase
- iPSC
- induced pluripotent stem cell
- iMN
- induced motor neuron
- LAMP1
- Lysosomal Associated Membrane Protein 1
- NMDA
- N-methyl-D-aspartate
- PBS
- phosphate buffered saline
- PI5K
- Phosphatidylinositol 5-kinase
- PR
- proline-arginine repeat DPR
- RAN
- repeat-associated non-AUG