# Precise excision of expanded GGC repeats in NOTCH2NLC via CRISPR/Cas9 for treating neuronal intranuclear inclusion disease

## TL;DR

Researchers developed a precise CRISPR-based gene-editing strategy to treat neuronal intranuclear inclusion disease by removing harmful GGC repeats in the NOTCH2NLC gene.

## Contribution

A highly specific CRISPR/spCas9 approach that excises GGC repeats in NOTCH2NLC without affecting similar genes is introduced.

## Key findings

- Precise excision of GGC repeats in NOTCH2NLC was achieved without off-target effects.
- The therapy alleviated neuropathological and behavioral abnormalities in NIID models.
- Efficacy was validated in human cell lines, iPSCs, and transgenic mouse models.

## Abstract

Neuronal intranuclear inclusion disease (NIID) is an adult-onset neurodegenerative disease caused by expanded GGC repeats in the 5’ untranslated region of the human-specific NOTCH2NLC gene. The high sequence similarity between NOTCH2NLC and its paralogs poses a significant challenge for precise gene editing. Here, we develop a CRISPR/spCas9-based gene-editing strategy that precisely excises the expanded GGC repeats in NOTCH2NLC without detectable off-target effects on the highly homologous NOTCH2/NOTCH2NL family genes (<2% sequence divergence at this locus). The efficacy, specificity and safety of this approach are rigorously validated across multiple experimental models, including human cell lines, NIID iPSCs, and our previously established transgenic NIID mouse model. Our results demonstrate that precise excision of the expanded GGC repeats effectively alleviates NIID-related neuropathological, molecular and behavioral abnormalities. This study establishes the proof of concept for genome editing as a therapeutic strategy for NIID and other related repeat expansion disorders.

NIID is a neurodegenerative disease caused by GGC repeat expansions within NOTCH2NLC gene. Here, authors develop a precise gene-editing therapy that effectively treats the disease in multiple models.