Abstract
TDP-43 is a central RNA binding protein (RBP) involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). Post-mortem tissue from about 97 percent of individuals with ALS presents TDP-43 aggregates, and TDP-43 proteinopathy is also common in other neurodegenerative diseases such as Dementia.
Mutations in TDP-43 that cause ALS affect its condensation properties. Less is known about the role of TDP-43 condensation in the selection of specific endogenous RNA binding sites, and thereby regulation of RNAs. To address the question of TDP-43’s RNA specificity, Martina Hallegger and colleagues created different TDP-43 variants in several cell systems. They introduced deletions and mutations into the C-terminal intrinsically disordered region (IDR) of TDP-43 that change the condensation properties on a gradient from negative to positive effects both in vitro and in vivo.
Using UV crosslinking and immunoprecipitation (iCLIP) and 3′ mRNA-seq, the team showed that TDP-43 condensation promotes its efficient assembly on a subset of RNA binding sites that are characterized by unique sequence features, including a highly multivalent arrangement of GU-rich motifs.
Hallegger and colleagues established that the conserved region (CR) within the IDR is crucial for efficient condensation of TDP-43 and evaluated how CR mutations that affect condensation properties impact TDP-43’s RNA binding and regulatory functions. Notably, they find that point mutations in the CR have the same gradient of effects at multiple levels: in vitro condensation, the formation and dynamics of TDP-43 foci in cell nuclei, binding to specific RNA sequences across the transcriptome, and regulation of RNA-processing. Their findings established that altered condensation properties of TDP-43 can selectively fine-tune its RNA-regulatory networks by modulating its RNA interactions. They speculated that ALS-associated alteration in condensation would interfere with this proper network regulation, particularly early in disease, and have profound effects on TDP-43 autoregulation.
Speaker’s biography
Martina Hallegger, PhD
RNA-network Biochemist
The Francis Crick Institute
Martina Hallegger’s most recent position was as the MND Association Lady Edith Wolfson Senior Non-Clinical Fellow at the Institute of Neurology, University College London and the Francis Crick Institute, where she is currently an independent senior research fellow. She began her scientific career during her postgraduate work at the University of Vienna and in a post-doctoral post in the department of biochemistry in Cambridge with the main objective of uncovering how genetic information is amplified by combinatorial mechanisms of alternative splicing and RNA editing. Hallegger developed a strong background in molecular and RNA biology and global transcriptome analysis. At the University of Oxford, she investigated how non-coding RNAs shape cell function, particularly in neurons affected in Parkinson’s disease.
Hallegger’s current research investigates how deregulated RNA metabolism contributes to the earliest events in the molecular pathogenesis of ALS and dementia and how to modulate this for therapeutic interventions. By applying high-throughput methods like iCLIP (cross-linking Immuno-precipitation), RNAseq, and proteomics, Hallegger investigates the central role of RNA-protein condensates in these diseases. The concentration of biopolymers via condensation is fundamental to cellular organization and physiology, and her research focuses on its effect on gene regulation. Hallegger is particularly interested in how the altered condensation properties of the RNA-binding protein TDP-43, which is central to ALS pathology, contribute to altered RNA metabolism in cell lines and in vitro.
