Cell environment shapes TDP-43 function: implications in neuronal and muscle disease

Abstract

TDP-43 aggregation and redistribution have been recognised as a hallmark of amyotrophic lateral sclerosis, frontotemporal dementia and other neurological disorders. While TDP-43 has been studied extensively in neuronal tissues, TDP-43 inclusions have also been described in the muscle of inclusion body myositis patients, highlighting the need to understand the role of TDP-43 beyond the central nervous system. Using RNA-seq we performed the first direct comparison of TDP-43-mediated transcription and alternative splicing in muscle (C2C12) and neuronal (NSC34) mouse cells. Our results clearly show that TDP-43 displays a tissue-characteristic behaviour targeting unique transcripts in each cell type. This is not due to variable transcript abundance but rather due to cell-specific expression of RNA-binding proteins, which influences TDP-43 performance. Among splicing events commonly dysregulated in both cell lines, we identified some that are TDP-43-dependent also in human cells and show that inclusion levels of these alternative exons appear to be differentially altered in affected tissues of FTLD and IBM patients. We therefore propose that TDP-43 dysfunction, reflected in aberrant splicing, contributes to disease development but it does so in a tissue- and disease-specific manner.

Unraveling the toxic effects mediated by the neurodegenerative disease–associated S375G mutation of TDP-43 and its S375E phosphomimetic variant

“…As a second functional analysis, we then compared the levels of endogenous POLDIP3 exon 3 inclusion in all three stable clones after 48 h upon the induction. The event was chosen because it represents one of the best readouts of TDP-43 splicing activity (31,32). Figure 1C shows that following induction, both the S375G and S375E mutants behaved exactly like the WT protein, in terms of keeping the same inclusion/ exclusion ratio of exon 3 following their induction (i.e., 80% POLDIP3 exon 3 inclusion).…”

Truncating Variants in RFC1 in Cerebellar Ataxia, Neuropathy, and Vestibular Areflexia Syndrome

“…In order to validate anti-RFC1-p140 mouse monoclonal (1:2'500, kind gift of Ulrich Hubscher 27 ), we performed RFC1 gene silencing as described in 28 . Briefly, HEK293 human neuroblastoma (ECACC) were cultured in a T75 flask and maintained in DMEM (Thermo Fisher Scientific) supplemented with 10% FBS (Thermo Fisher Scientific) at 37°C in a 5% CO2 humidified incubator.…”

Expanding the TDP-43 Proteinopathy Pathway From Neurons to Muscle: Physiological and Pathophysiological Functions

“…When looking at splicing, tissue-specific functions for TDP-43 emerge, namely between neuronal and muscular tissues. In neurons, TDP-43 regulates the splicing patterns of transcripts encoding proteins involved in neuronal processes and the number of splicing events is higher when compared to muscle cells (Šušnjar et al, 2021;Tollervey et al, 2011). The repertory of RNA binding proteins (RBPs) present in neurons is different from that in muscle cells, which also exhibit relatively higher expression levels.…”