Linking RNA methylation and TDP43 pathology in ALS/FTD models

PROJECT SUMMARY/ABSTRACT Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are related neurodegenerative diseases with few available disease-modifying therapies. In over 95% of individuals with ALS and 50% of individuals with FTD, affected neurons display cytoplasmic mislocalization and accumulation of transactive response element DNA/RNA binding protein of 43 kDa (TDP43). TDP43 is an essential regulator of RNA splicing and stability and is normally localized to the nucleus. As such, pathologic redistribution of TDP43 to the cytoplasm causes pervasive changes in gene expression, disrupting many integral cellular processes. Accumulating evidence underscores TDP43’s contribution to ALS/FTD pathogenesis, yet the mechanisms underlying its mislocalization remain unclear. We and others determined that TDP43 localization is heavily influenced by its RNA binding. In line with this, our recent work revealed widespread methylation of TDP43 substrates at the nitrogen-6 position of adenosine (m6A), a prevalent RNA modification. Physiologically, m6A modifications promote substrate binding by TDP43. Several TDP43 substrates are abnormally hypermethylated in ALS patient tissues, suggesting a potential mechanism for RNA dysregulation in disease. Based on these findings, I hypothesize that disease- associated RNA hypermethylation fundamentally increases RNA binding by TDP43, resulting in its cytoplasmic mislocalization and subsequent dysfunction. I will test this hypothesis in Aim 1 by examining the relationship between RNA methylation and TDP43 mislocalization in ALS post-mortem samples and human neuron disease models. In Aim 2, I will investigate how m6A modulates TDP43’s RNA binding on a site-specific basis. Ultimately, the goal of this proposal is to elucidate the mechanisms by which m6A modifications impact TDP43 binding, localization, and function. These studies may uncover novel mechanisms of neurodegeneration in ALS/FTD and identify potential therapeutic strategies to restore RNA homeostasis in these diseases. Additionally, the work outlined in this proposal will provide me the opportunity to develop key skills in experimental design, bioinformatics analysis, and collaborative research.