A G4C2 hexanucleotide repeat expansion in the C9orf72 gene is the most common genetic cause of ALS and FTLD (C9-ALS/FTLD) with cytoplasmic TDP-43 inclusions observed in regions of neurodegeneration. The accumulation of repetitive RNAs and dipeptide repeat protein (DPR) are two proposed mechanisms of toxicity in C9-ALS/FTLD and linked to impaired nucleocytoplasmic transport. Nucleocytoplasmic transport is regulated by the phenylalanine-glycine nucleoporins (FG nups) that comprise the nuclear pore complex (NPC) permeability barrier. However, the relationship between FG nups and TDP-43 pathology remains elusive. Our studies show that nuclear depletion and cytoplasmic mislocalization of one FG nup, NUP62, is linked to TDP-43 mislocalization in C9-ALS/FTLD iPSC neurons. Poly-glycine arginine (GR) DPR accumulation initiates the formation of cytoplasmic RNA granules that recruit NUP62 and TDP-43. Cytoplasmic NUP62 and TDP-43 interactions promotes their insolubility and NUP62:TDP-43 inclusions are frequently found in C9orf72 ALS/FTLD as well as sporadic ALS/FTLD postmortem CNS tissue. Our findings indicate NUP62 cytoplasmic mislocalization contributes to TDP-43 proteinopathy in ALS/FTLD.

RNA-binding proteins (RBPs) are associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), but the underlying disease mechanisms remain unclear. In an unbiased screen in Drosophila for RBPs that genetically interact with TDP-43, we found that downregulation of the mRNA export factor Ref1 (fly orthologue to human ALYREF ) mitigated TDP-43 induced toxicity. Further, Ref1 depletion also reduced toxicity caused by expression of the C9orf72 GGGGCC repeat expansion. Ref1 knockdown lowered the mRNA levels for these related disease genes and reduced the encoded proteins with no effect on a wild-type Tau disease transgene or a control transgene. Interestingly, expression of TDP-43 or the GGGGCC repeat expansion increased endogenous Ref1 mRNA levels in the fly brain. Further, the human orthologue ALYREF was upregulated by immunohistochemistry in ALS motor neurons, with the strongest upregulation occurring in ALS cases harboring the GGGGCC expansion in C9orf72 . These data support ALYREF as a contributor to ALS/FTD and highlight its downregulation as a potential therapeutic target that may affect co-existing disease etiologies. Electronic supplementary material The online version of this article (10.1186/s40478-019-0710-x) contains supplementary material, which is available to authorized users.

Purpose Epidermal growth factor receptor variant 3 (EGFRvIII) has been detected in several cancers where tumors expressing this truncated growth factor receptor demonstrate more aggressive behavior. The molecular mechanisms that contribute to EGFRvIII-mediated tumor progression that are amenable to targeted therapy are incompletely understood. The present study aimed to better define the role of src family kinases in EGFRvIII mediated cell motility and tumor growth of head and neck squamous cell carcinomas (HNSCC). Experimental Design HNSCC models expressing EGFRvIII were treated with dasatinib, a pharmacologic inhibitor of src family kinases (SFKs). Results SFK inhibition significantly decreased cell proliferation, migration and invasion of EGFRvIII-expressing HNSCC cells. Administration of dasatinib to mice bearing EGFRvIII-expressing HNSCC xenografts resulted in a significant reduction of tumor volume compared with controls. Immunoprecipitation with anti- c-Src, Lyn, Fyn and Yes antibodies followed by immunoblotting for phosphorylation of the SFK activation site (Y416) demonstrated specific activation of Lyn kinase in EGFRvIII expressing HNSCC cell lines and human HNSCC tumor specimens. Selective inhibition of Lyn using siRNA decreased cell migration and invasion of EGFRvIII- expressing HNSCC compared to vector-control cells. Conclusions These findings demonstrate that Lyn mediates tumor progression of EGFRvIII-expressing HNSCC where strategies to inhibit SFK may represent an effective therapeutic strategy.

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