C9orf72 poly-PR condensation induces nuclear TDP-43 pathology and is inhibited by RNA in an optogenetic cell model
Proteinaceous inclusions formed by C9orf72 derived dipeptide-repeat (DPR) proteins are a histopathological hallmark in ~50% of familial amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) cases. However DPR aggregation/inclusion formation could not be efficiently recapitulated in cell models for four out of five DPRs. In this study, using optogenetics, we achieved chemical-free poly-PR condensation/aggregation in cultured cells, with spatial and temporal control. Strikingly, nuclear poly-PR condensates had anisotropic, hollow-centre appearance, resembling anisosomes formed by aberrant TDP-43 species, and their growth was limited by RNA. These condensates induced abnormal TDP-43 granulation in the nucleus without the activation of stress response. Cytoplasmic poly-PR aggregates that formed under prolonged light stimulation were more persistent than its nuclear condensates, selectively sequestered TDP-43 in a demixed state and surrounded spontaneous stress granules. Our data suggest that poly-PR anisotropic condensation in the nucleus, causative of nuclear TDP-43 dysfunction, may constitute an early pathological event in C9-ALS/FTD. Anisosome-type condensates may represent a more common cellular pathology in neurodegeneration than previously thought. Highlights- Optogenetics can be used to model C9orf72 DPR condensation in cultured cells. - Opto-PR forms hollow nuclear condensates, and RNA limits their growth by fusion. - Opto-PR condensation leads to stress-independent TDP-43 pathology in the nucleus. - Cytoplasmic poly-PR assemblies are persistent and selectively sequester TDP-43. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=100 SRC="FIGDIR/small/581933v2_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@ccce86org.highwire.dtl.DTLVardef@ae2b3org.highwire.dtl.DTLVardef@a9880eorg.highwire.dtl.DTLVardef@236c32_HPS_FORMAT_FIGEXP M_FIG C_FIG