# Mechanisms of A-I RNA editing-mediated nuclear export of TDP-43

> **NIH NIH R21** · ST. JOSEPH'S HOSPITAL AND MEDICAL CENTER · 2022 · $345,566

## Abstract

TAR DNA binding protein – 43 (TDP-43) is a critical RNA binding protein that is intimately involved in many  aspects of RNA metabolism. While primarily localized to the nucleus, TDP-43 shuttles between the nucleus and  the cytoplasm performing its physiological functions. As an aggregation prone protein, TDP-43 is known to  accumulate and from prion-like solid aggregates in the cytoplasm of cells leading to the sequestration of nuclear  TDP-43. This behavior of TDP-43 has been well established as a pathological hallmark of a neurodegenerative  disease spectrum encompassing amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD) and has  been described in Alzheimer’s disease and related dementias. Pathological cytoplasmic TDP-43 inclusions have  been hypothesized to contribute to disease pathogenesis through both a nuclear depletion and the cytoplasmic  aggregation. Despite extensive research, mechanisms that initiate this pathology under disease conditions  remain elusive. Recent studies in our laboratory showed that aberrant RNA A-I editing is present in multiple brain  regions of C9orf72 ALS/FTD, where we detected bidirectional changes in A-I editing. Since then, we have  generated preliminary data suggesting that TDP-43 nuclear export can be regulated via Adenosine Deaminase  Acting on double stranded RNA (ADAR)-mediated A-I RNA editing. We show that enhancing RNA A-I editing  through ADAR2 overexpression in mammalian cell lines induces TDP-43 translocation to the cytoplasm requiring functional RNA binding domains of TDP-43. In contrast, the overexpression of catalytically inactive ADAR2 does  not alter the nuclear localization of TDP-43. These findings led us to hypothesize that aberrant increases in A-I editing induces TDP-43 cytoplasmic mislocalization through an RNA dependent mechanism. To  determine if this editing induced TDP-43 nuclear export also occurs in a neuronal environment, we will expand  on our preliminary data and examine human induced pluripotent stem cell (iPSC) differentiated into motor  neurons for A-I editing-mediated TDP-43 nuclear export. We will validate A-I RNA editing mediated cytoplasmic  accumulation of TDP-43 in iPSC-MNs expressing doxycycline inducible Tet-On ADAR2 constructs: wildtype  ADAR2, a catalytically inactive ADAR2 (ADAR2E396A) and a catalytically hyperactive ADAR2 (ADAR2E488Q). To  address the effects of RNA-editing induced TDP-43 mislocalization on TDP-43 function, we will examine TDP-43 inclusions for disease-relevant characteristics (Aim1). To determine the identity of mRNAs bound to TDP-43  and potentially being necessary for A-I RNA editing-mediated mislocalization, we will perform eCLIP-seq on  iPSC-MNs genetically altered for hypo and hyper-editing as described in Aim1. In addition, we will perform eCLIP  in C9orf72 iPSC-MNs to compare RNA-editing induced TDP-43 bound transcripts to those associated with  endogenous disease (Aim 2). Finally, in Aim 3, we will perform exploratory studi...

## Key facts

- **NIH application ID:** 10575984
- **Project number:** 1R21NS130492-01
- **Recipient organization:** ST. JOSEPH'S HOSPITAL AND MEDICAL CENTER
- **Principal Investigator:** Rita Sattler
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $345,566
- **Award type:** 1
- **Project period:** 2022-09-22 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10575984

## Citation

> US National Institutes of Health, RePORTER application 10575984, Mechanisms of A-I RNA editing-mediated nuclear export of TDP-43 (1R21NS130492-01). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10575984. Licensed CC0.

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