CRISPR/CasRx-Mediated Silencing of HTT Shows Therapeutic Potential in Huntington’s Disease Models

Huntington's disease (HD) is a devastating neurodegenerative disorder caused by the expansion of CAG repeats in exon 1 of the huntingtin-encoding gene, HTT. Strategies to silence the expression of mutated huntingtin protein have been explored as a new therapeutic avenue to treat HD, and recent advances in gene-editing and RNA-targeting raise hopes that new treatments are on the horizon for HD patients.

In a recent study, researchers in China sought to silence mutant human HTT exon 1 using CasRx – a programmable CRISPR–Cas system that targets RNA for efficient knockdown and splicing modulation – in conjunction with target-specific guide RNAs.

They tested their strategy in various models including human embryonic kidney (HEK) 293T cells, a mouse model of HD known as HD 140Q-KI mice and a pig model of HD. Among their key findings were that targeting exon 1 with CRISPR/CasRx significantly reduced HTT mRNA levels and mutant HTT protein expression in all tested models, while the treatment coincided with improved motor function and reduced HD symptoms in both mouse and pig models.

Experiments in HD 140Q-KI mice revealed that silencing of HTT exon 1 effectively alleviated gliosis (inflammation) at different disease stages, while in HD-KI pigs, the treatment reduced neurodegeneration and partially normalised HTT gene expression dysregulation. The researchers report that their approach showed high specificity without significant off-target effects, where off-targets were assessed using a combination of RT-PCR and RNA sequencing on a panel of predicted off-targets for each guide RNA used.

The findings, which were published yesterday in Molecular Neurodegeneration, suggest that CRISPR/CasRx-mediated RNA editing could be a promising therapeutic strategy for HD, as it reduces mutant HTT expression and alleviates HD-associated neuropathology in human cells and animal models of HD.

Read the full open-access article entitled 'RNA-Targeting CRISPR/CasRx system relieves disease symptoms in Huntington’s disease models' in Molecular Neurodegeneration here.