CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeats) genome editing technologies have transformed the therapeutic landscape for [neurodegenerative /diseases by enabling precise correction or inactivation of disease-causing genes. Unlike antisense-oligonucleotide-therapy (ASOs), which require repeated dosing and produce temporary knockdown, CRISPR can achieve permanent genetic modification in a single treatment—a transformative prospect for monogenic neurodegenerative disorders such as huntington-pathway (HD), familial alzheimers (fAD), familial parkinsons (fPD), and als (ALS). [@akyuz2024]
The CRISPR toolkit has expanded beyond the original Cas9 nuclease to include base editors, prime editors, CRISPRi/CRISPRa for gene regulation, and RNA-targeting Cas13 systems—each offering distinct advantages for neurological applications where off-target DNA cuts in post-mitotic neurons pose irreversible risks (Akyuz et al., 2024; Bhatt et al., 2025). [@bhatt2025]
The canonical system uses the Cas9 nuclease guided by a single-guide RNA (sgRNA) to create a double-strand break (DSB) at a specific genomic locus. In neurons, DSBs are repaired primarily by non-homologous end joining (NHEJ), which can inactivate a gene by introducing insertions/deletions (indels). [@bhatt2025a]
Applications: Disruption of mutant alleles (e.g., mutant htt, sod1-protein, app [@ref]
Limitations: Off-target DSBs in post-mitotic neurons are permanent and uncorrectable; risk of large deletions, translocations, or chromothripsis. [@refa]
Base editors (cytosine base editors, CBE; adenine base editors, ABE) convert one base pair to another (C→T or A→G) without creating DSBs. This is safer for neurons and ideal for correcting point mutations. [@ekman2019]
Applications: Correcting psen1 and psen2 missense mutations in familial AD; lrrk2 G2019S mutation in PD; specific sod1-protein mutations in ALS. [@refb]
Prime editors use a Cas9 nickase fused to a reverse transcriptase, guided by a prime editing guide RNA (pegRNA) that encodes the desired edit. Prime editing can make all 12 types of point mutations, small insertions, and small deletions without DSBs. [@lin2018]
Applications: Precise correction of expanded CAG repeats in HD; correction of specific mutations in fAD and fPD. [@refc]
Catalytically dead Cas9 (dCas9) fused to transcriptional repressors (CRISPRi) or activators (CRISPRa) modulates gene expression without altering DNA sequence. [@gillmore2021]
Advantages: No permanent DNA alteration; reversible; lower risk of off-target damage. [@bhatt2025b]
Cas13 systems target and degrade specific RNA transcripts, functioning as programmable RNA knockdown tools. Unlike DNA-targeting systems, Cas13 leaves the genome intact. [@bhatt2025c]
Applications: Degradation of mutant htt mRNA, c9orf72 repeat RNA, or toxic tdp-43 transcripts. [@bhatt2025d]
HD is the most advanced neurodegenerative target for CRISPR, given its monogenic etiology (expanded CAG repeat in [HTT): [@bhatt2025e]
Allele-specific silencing: CRISPR-Cas9 can selectively inactivate the mutant htt allele while preserving normal htt by targeting SNPs linked to the disease haplotype. This avoids the problem of total htt loss-of-function, which is developmentally lethal (Monteys et al., 2017). [@doudna2014]
Repeat excision: Cas9 with two flanking sgRNAs can excise the expanded CAG repeat, replacing it with a normal-length repeat. This has been demonstrated in HD patient-derived iPSC neurons (Dabrowska et al., 2018).
CRISPRi approach: dCas9-KRAB targeted to the htt promoter region suppresses mutant htt expression by 60-80% in mouse striatal neurons without DNA cleavage.
In vivo delivery: AAV-packaged CRISPR targeting mutant htt reduced huntingtin aggregates and improved motor function in HD mouse models (Ekman et al., 2019).
CRISPR approaches in AD target multiple pathogenic genes:
app editing: CRISPR-mediated introduction of the protective A673T (Icelandic) mutation in app reduces amyloid-beta production by ~40%. This mutation decreases bace1.
psen1 correction: Base editing can correct specific presenilin mutations that cause familial Alzheimer's Disease. Over 300 psen1 mutations are known, many of which are single nucleotide changes amenable to base editing.
**apoe using base editors has been demonstrated in human iPSC-derived astrocytes and neurons, reducing amyloid-beta production and tau] hyperphosphorylation (Lin et al., 2018).
trem2 activation: CRISPRa to upregulate trem2 expression in microglia/entities/microglia. Adenine base editors can revert the pathogenic G→A mutation with high efficiency in patient iPSC-derived dopaminergic neurons.
alpha-synuclein (SNCA) reduction: CRISPRi-mediated downregulation of SNCA expression reduces alpha-synuclein aggregation. SNCA gene duplication/triplication causes familial PD, and even partial reduction of wild-type SNCA may be therapeutic.
gba correction: GBA1 mutations (the most common genetic risk factor for PD) can be corrected by base or prime editing, restoring glucocerebrosidase activity and improving lysosomal function.
pink1/prkn enhancement: CRISPRa to upregulate mitophagy genes, enhancing clearance of damaged mitochondrial-dynamics.
sod1-protein silencing: CRISPR-Cas9 disruption of mutant SOD1 in the SOD1-G93A mouse model reduced mutant SOD1 protein levels by ~50% and extended survival. This approach complements the tofersen strategy.
c9orf72 repeat excision: Cas9 with flanking guides can excise the hexanucleotide repeat expansion, eliminating both RNA foci and dipeptide repeat protein production (Selvaraj et al., 2018).
fus correction: Base editing of FUS mutations that disrupt nuclear localization (affecting the PY-NLS recognized by transportin-1), restoring proper nucleocytoplasmic transport.
| Disease | CRISPR Target | Approach |
|---|---|---|
| friedreichs-ataxia | GAA repeat in FXN | Repeat excision, CRISPRa for FXN upregulation |
| SCA (various) | Expanded CAG in ATXN genes | Allele-specific knockout or repeat excision |
| spinal-muscular-atrophy | SMN2 exon 7 inclusion | Base editing to convert SMN2 → SMN1-like |
| batten-disease | CLN gene mutations | Gene correction via HDR or base editing |
| wilson-disease | ATP7B mutations | Gene correction |
| rett-syndrome | MECP2 mutations | Gene correction, CRISPRa |
The greatest challenge for CRISPR-based neurotherapeutics is delivering editing machinery across the blood-brain-barrier to target cells in the CNS.
Adeno-associated virus (AAV):
Lentiviral vectors:
Lipid nanoparticles (LNPs):
Extracellular vesicles/exosomes:
Polymer nanoparticles:
CRISPR-Cas9 can cut at genomic sites with partial sgRNA complementarity. In post-mitotic neurons, off-target DSBs are irreversible and could activate oncogenes, inactivate tumor suppressors, or disrupt essential genes.
Mitigation strategies:
| Disease | Target | Stage | Notes |
|---|---|---|---|
| HD | htt | Preclinical (advanced) | Multiple AAV-CRISPR approaches in NHP studies |
| als (SOD1) | SOD1 | Preclinical | Complementing approved ASO (tofersen |
| AD (fAD) | app, psen1 | Preclinical | APOE4→APOE3 conversion in development |
| PD (LRRK2) | LRRK2 | Preclinical | Base editing approach |
| SCA | ATXN genes | Preclinical | AAV-delivered Cas9 |
| Transthyretin amyloidosis | TTR | Phase I (Intellia NTLA-2001) | First in vivo CRISPR therapy for a systemic disease; proof of concept for neurodegeneration |
The Intellia Therapeutics NTLA-2001 trial for transthyretin amyloidosis—using LNP-delivered Cas9 to inactivate TTR in the liver—demonstrated >90% reduction in serum transthyretin after a single dose, providing the first clinical proof that in vivo CRISPR editing is feasible and effective (Gillmore et al., 2021).
The study of Crispr Gene Editing For Neurodegenerative Diseases has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
| Method | Advantage | Disadvantage |
|---|---|---|
| AAV Vectors | Long-term expression | Small cargo capacity |
| Lentivirus | Large cargo | Integration risk |
| Lipid NPs | Safe, scalable | Transient effect |
| Electroporation | High efficiency | Invasive |
| Gene | Disease | Strategy |
|---|---|---|
| APP | AD | Reduce Aβ production |
| SNCA | PD | Reduce α-synuclein |
| SOD1 | ALS | Inactivate mutant |
| HTT | HD | Reduce mutant HTT |