Abbassi, Y. | bioRxiv Science

bioRxiv2023

Axon guidance genes are regulated by TDP-43 and RGNEF through the rate of long-intron processing.

Rho guanine nucleotide exchange factor (RGNEF) is a guanine nucleotide exchange factor (GEF) mainly involved in regulating the activity of Rho-family GTPases. Previous work has shown that RGNEF inclusions in the spinal motor neurons of ALS patients co-localise with TDP-43, the major RNA binding protein aggregating in the brain and spinal cord of ALS patients. To further characterise their relationship, we have compared the transcriptomic profiles of neuronal-like cells depleted of TDP-43 and RGNEF and show that these two factors predominantly act in an antagonistic manner when regulating the expression of axon guidance genes. From a mechanistic point of view, our experiments show that the effect of these factors on the processivity of long introns can explain their mode of action. Our findings highlight that neurodegenerative processes at the RNA level can often represent the result of combinatorial interactions between different RNA binding factors, leading to a better understanding of pathogenic mechanisms occurring in patients where more than one specific protein may be aggregating in their neurons.

neuroscience↗

bioRxiv2021

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

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.

neuroscience↗