Precise Excision of the CAG Tract from the Huntingtin Gene by Cas9 Nickases

Area of Science:

• Genetics and Molecular Biology
• Neuroscience
• Gene Therapy

Background:

• Huntington's disease (HD) is a neurodegenerative disorder caused by expanded CAG repeats in the huntingtin gene (HTT).
• Mutant huntingtin protein accumulation leads to neuronal dysfunction and selective cell death in the striatum.
• Current therapies aim to reduce mutant HTT expression using antisense oligonucleotides, RNA interference, or CRISPR/Cas9.

Purpose of the Study:

• To investigate the precise excision of CAG repeat tracts from the HTT gene using a paired Cas9 nickase strategy.
• To evaluate the efficacy of this approach in inactivating the HTT gene and abrogating mutant huntingtin synthesis.
• To assess the potential of this method as a therapeutic tool for Huntington's disease and other polyglutamine disorders.

Main Methods:

• Utilized a paired Cas9 nickase strategy for precise excision of CAG repeat tracts.
• Employed Huntington's disease patient-derived fibroblasts with varying CAG repeat lengths as a model system.
• Assessed gene inactivation and huntingtin protein synthesis following repeat excision.

Main Results:

• Successfully demonstrated precise excision of the CAG repeat tract from the HTT gene.
• Achieved gene inactivation and abrogated huntingtin synthesis in a manner independent of CAG repeat length.
• Validated the safety and specificity of the Cas9 nickase approach.

Conclusions:

• The paired Cas9 nickase strategy offers a precise method for excising expanded CAG repeats in Huntington's disease.
• This approach effectively inactivates the HTT gene and halts mutant huntingtin production.
• This gene editing technique presents a promising therapeutic avenue for Huntington's disease and other polyglutamine disorders.