ORCID
https://orcid.org/0000-0003-0022-9975
Date of Award
12-19-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Matrin-3 (MATR3) is a disordered DNA- and RNA-binding protein which has been implicated in amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) through pathological inclusions and patient mutations. Despite the development of various higher order models of MATR3 proteinopathy, the intrinsic properties of MATR3, molecular determinants of its proteotoxicity, and impact of its disease-associated mutations remain unclear. To address these key gaps, we developed a yeast model and a recombinant protein model of MATR3 which provide platforms to study MATR3 outside of its native environment. In our yeast model, we found that exogenous MATR3 expression is toxic and forms dynamic shell-like nuclear puncta. Introduction of MATR3 disease-associated mutations altered condensate morphology and dynamics. The genetic tractability of our yeast model allowed investigation of the molecular determinants of MATR3 proteotoxicity through domain deletion and truncation constructs. We observed that MATR3 RNA recognition motifs drove cellular toxicity. Coexpression of MATR3 with potentiated variants of Hsp104, a yeast protein disaggregase, rescued its cellular toxicity presumably through protein remodeling. We utilized our recombinant protein model of MATR3 to investigate its intrinsic phase separation and aggregation properties. Surprisingly, we observed that MATR3 forms nanometer-scale size-limited spherical and worm-like microphases rather than amorphous aggregates or amyloid fibers. Additionally, micron-scale crowder-induced assemblies of MATR3 lacked liquid-like features such as fusion and increasing size. We observed that the presence of short RNA probes or mutations in MATR3 RNA recognition motifs restricted worm-like microphase length. In contrast, MATR3 disease-associated mutations formed elongated worm-like microphases which persisted in the presence of RNA. Collectively, this work uncovered foundational knowledge about the intrinsic material properties of MATR3 and the molecular determinants of its proteotoxicity. We have discovered that MATR3 assemblies are governed by microphase separation, which is distinct from canonical liquid-liquid phase separation governing many disordered RNA binding proteins in ALS/FTD. In both our yeast and recombinant protein models, we have elucidated that MATR3 assembly morphologies and dynamics are dysregulated by ALS/FTD-associated mutations in MATR3.
Language
English (en)
Chair and Committee
Meredith Jackrel
Recommended Citation
Sprunger, Macy L., "Determinants and Dysregulation of Matrin-3 Material Properties in Amyotrophic Lateral Sclerosis" (2023). Arts & Sciences Electronic Theses and Dissertations. 3208.
https://openscholarship.wustl.edu/art_sci_etds/3208