Electronic Thesis and Dissertation Repository

Thesis Format



Master of Science


Pathology and Laboratory Medicine


Strong, Michael J.


The presence of neuronal cytoplasmic inclusions (NCIs) composed of RNA-binding proteins (RBPs) and neurofilaments is considered to be ALS’s neuropathological hallmark. RGNEF has been previously shown to interact with TDP-43 and to have a regulatory effect on the expression levels of NEFL mRNA and NFL protein in vitro. Here, I examined the mechanism of the RGNEF N-terminus, leucine-rich domain (LeuR) domain’s interaction with TDP-43. I observed that the minimal domain required is 110 amino acids (LeuR110), that the Ankyrin domain adjacent to LeuR110 does not participate, and that LeuR110 forms of a high molecular weight complex with TDP-43 in vitro consistent with the co-aggregation of LeuR242 and TDP-43 in double transgenic drosophila melanogaster. I also observed that RGNEF interacts directly with and destabilizes the TARDBP mRNA 3’UTR. These findings support that RGNEF interacts with TDP-43 through the formation of a high molecular weight complex and the down-regulation of its expression.

Summary for Lay Audience

Amyotrophic Lateral Sclerosis (ALS) is a progressive, adult-onset disease characterized by the degeneration of motor neurons. In the cytoplasm of neuronal cells, the buildup of RNA-binding proteins (RBPs), neurofilaments and other proteins are considered to be the disease’s hallmark. Among these proteins, Rho guanine nucleotide exchange factor (RGNEF) has been identified as a key element in the development of ALS, where it accumulates in the cytoplasm of motor neurons. Previously, RGNEF has been shown to interact with another protein TDP-43 and to regulate a neurofilament protein NFL. Here, I focused on the mechanism of interaction between TDP-43 and a region of RGNEF, leucine-rich (LeuR). I observed that a minimal domain of LeuR interacts with TDP-43 by forming a complex of proteins, consistent with our observations in the brain and eye tissue of an ALS fly model. In addition to the interacting mechanism, I studied the role of RGNEF in the regulation of TDP-43. I observed that in the presence of the LeuR, there is a downregulation in TDP-43 levels. By defining the role of the interaction between two ALS-associated RBPs, RGNEF and TDP-43, we can get a step further into identifying a potential therapeutic target in ALS.