Epigenetic Editing and CRISPR Approaches in CBS/PSP

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Epigenetic Editing and CRISPR Approaches in CBS/PSP

Introduction

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Epigenetic Editing and CRISPR Approaches in CBS/PSP

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Epigenetic Editing and CRISPR Approaches in CBS/PSP</th>
</tr>
<tr>
<td class="label">Component</td>
<td>Function</td>
</tr>
<tr>
<td class="label">dCas9-DNMT3A</td>
<td>Adds methyl groups to CpG sites</td>
</tr>
<tr>
<td class="label">dCas9-TET</td>
<td>Removes methyl groups (demethylation)</td>
</tr>
<tr>
<td class="label">dCas9-DNMT3L</td>
<td>Catalytic domain for methylation</td>
</tr>
<tr>
<td class="label">Modification</td>
<td>Enzyme (dCas9 fusion)</td>
</tr>
<tr>
<td class="label">H3K9ac (activation)</td>
<td>dCas9-p300</td>
</tr>
<tr>
<td class="label">H3K9me3 (repression)</td>
<td>dCas9-LSD1</td>
</tr>
<tr>
<td class="label">H3K27ac</td>
<td>dCas9-p300</td>
</tr>
<tr>
<td class="label">H3K27me3 (repression)</td>
<td>dCas9-PRC2</td>
</tr>
<tr>
<td class="label">Study</td>
<td>Model</td>
</tr>
<tr>
<td class="label">Gao et al. 2023</td>
<td>P301S mice</td>
</tr>
<tr>
<td class="label">Chen et al. 2024</td>
<td>iPSC-FTD neurons</td>
</tr>
<tr>
<td class="label">Liu et al. 2023</td>
<td>Primary neurons</td>
</tr>
<tr>
<td class="label">Hilton et al. 2023</td>
<td>Mouse neurons</td>
</tr>
<tr>
<td class="label">Criterion</td>
<td>Score (0-10)</td>
</tr>
<tr>
<td class="label">Mechanistic Rationale</td>
<td>9</td>
</tr>
<tr>
<td class="label">Preclinical Evidence</td>
<td>6</td>
</tr>
<tr>
<td class="label">Delivery Feasibility</td>
<td>5</td>
</tr>
<tr>
<td class="label">Safety Profile</td>
<td>7</td>
</tr>
<tr>
<td class="label">Durability</td>
<td>7</td>
</tr>
<tr>
<td class="label">Reversibility</td>
<td>8</td>
</tr>
<tr>
<td class="label">CBS/PSP Specificity</td>
<td>8</td>
</tr>
<tr>
<td class="label">Combination Potential</td>
<td>8</td>
</tr>
<tr>
<td class="label">Timeline to Clinic</td>
<td>4</td>
</tr>
<tr>
<td class="label">Patient Selection</td>
<td>6</td>
</tr>
<tr>
<td class="label">NET Score</td>
<td>54/70</td>
</tr>
<tr>
<td class="label">Medication</td>
<td>Epigenetic Interaction</td>
</tr>
<tr>
<td class="label">Levodopa</td>
<td>No direct interaction</td>
</tr>
<tr>
<td class="label">Rasagiline</td>
<td>No direct interaction</td>
</tr>
</table>

Epigenetic editing represents a frontier in neurodegenerative disease therapy, offering the ability to modulate gene expression without altering the underlying DNA sequence. For corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP), these technologies hold particular promise because they can target disease-relevant genes while potentially avoiding the permanent genomic alterations required by traditional CRISPR gene editing.

This section covers:

dCas9-DNA methyltransferases for targeted DNA methylation

Histone modification editing using CRISPR-dCas9 fusions

CRISPRa/CRISPRi for tau pathology

NET assessment for CBS/PSP patient

Epigenetic Editing Technologies

Overview of Epigenetic Mechanisms

Mermaid diagram (expand to render)

DNA Methylation Editing

DNA methylation at gene promoter regions typically silences gene expression. CRISPR-dCas9 fused to DNA methyltransferases (DNMT3A, DNMT3L) can induce targeted DNA methylation[@khalil2024]:

Advantages for CBS/PSP:

Can reduce expression of mutant tau without DNA sequence changes
Potential for long-lasting effects through stable DNA methylation
Reversible if needed (TET demethylases)

Current Status:

Preclinical validation in tauopathy models ongoing
Off-target effects being characterized
Delivery to neurons optimized in research settings

Histone Modification Editing

Histone modifications alter chromatin structure and gene accessibility. CRISPR-dCas9 can be fused to histone-modifying enzymes for precise epigenetic changes[@yi2024]:

Key Applications in CBS/PSP:

Neurotrophin upregulation: dCas9-p300 targeting BDNF promoter to increase expression

Tau reduction: dCas9-KRAB targeting MAPT promoter for transcriptional repression

Synaptic gene activation: dCas9-VP64 for synaptic plasticity genes

CRISPRa/CRISPRi for Tau Pathology

CRISPR Activation (CRISPRa)

CRISPRa uses dCas9 fused to transcriptional activators (VP64, VPR, SunTag) to increase gene expression[@chen2024]:

Therapeutic Targets:

BDNF: Increase neurotrophic support
GDNF: Enhance dopaminergic neuron survival
TREM2: Potentially beneficial microglial activation variants
Progranulin (GRN): For GRN mutation carriers

Delivery approach:

AAV vectors with neuron-specific promoters
Temporal window: early disease stages for maximum benefit

CRISPR Interference (CRISPRi)

CRISPRi uses dCas9 fused to transcriptional repressors (KRAB domain) to reduce gene expression[@gao2023]:

Mermaid diagram (expand to render)

Advantages:

Reversible (can be turned off)
No DNA sequence changes
Precise targeting with gRNA design

Clinical Research Status

Preclinical Progress

Challenges for CNS Application

Delivery: AAV cargo capacity limits dual gRNA + dCas9 systems

Cell specificity: Targeting appropriate neurons (cortical, basal ganglia)

Off-target effects: Epigenetic changes must be carefully controlled

Durability: Balancing transient vs. permanent effects

Emerging Solutions

Split-intein systems: Divide large epigenetic editors
MiniCas9 variants: Smaller nuclease for increased cargo space
Self-deleting systems: Turn off editing after therapeutic effect
BBB-crossing vectors: AAV-PHP.eB and related variants

NET Assessment for CBS/PSP

Epigenetic Editing Scores

Strengths

Direct targeting of tau expression without DNA sequence alteration
Potential for long-lasting but reversible effects
Multiple target genes (MAPT, GRN, GBA) relevant to CBS/PSP
Strong mechanistic basis

Weaknesses

CNS delivery remains a significant challenge
Limited clinical data in neurodegenerative disease
Off-target epigenetic effects require careful monitoring
Not yet suitable for patients without identified genetic targets

Patient-Specific Considerations

Current Medications

Patient Eligibility

Best candidates for epigenetic editing approaches:

Patients with confirmed MAPT mutations (familial CBS/PSP)

GBA variant carriers (potential for GBA-targeted editing)

GRN mutation carriers (progranulin upregulation)

Younger patients with earlier disease stage

Timeline:

Current status: Preclinical
IND-enabling studies: 3-5 years
Clinical trials: 5-10 years
Standard of care: 10+ years

Integration with Treatment Plan

Cross-Links

[[Section 107: CRISPR-Based Therapies in CBS/PSP](/therapeutics/section-107-crispr-therapies-cbs-psp)](/diseases/progressive-supranuclear-palsy)
[Gene Therapy](/therapeutics/gene-therapy) — AAV delivery methods
[[Epigenetic Therapies for Neurodegeneration](/therapeutics/epigenetic-therapies-neurodegeneration)](/diseases/neurodegeneration)
[[MAPT Gene](/genes/mapt)](/proteins/tau)

Research Participation

Patients interested in epigenetic editing approaches should:

Pursue genetic testing to identify potential targets

Consider participating in natural history studies

Contact centers conducting gene therapy research

Patient Action Items

Genetic consultation: Discuss genetic testing options with neurologist

Research awareness: Monitor ClinicalTrials.gov for epigenetic editing trials

Center evaluation: Consider evaluation at academic centers with gene therapy programs

Baseline documentation: Establish genetic baseline for future reference

Conclusion

Epigenetic editing technologies offer a promising approach for CBS/PSP by allowing targeted modulation of disease-relevant genes without permanent DNA sequence changes. While clinical application remains years away, the rapid advancement of CRISPR-dCas9 tools and improved CNS delivery methods provide genuine hope for patients with genetic forms of atypical parkinsonism.

The NET assessment score of 54/70 (77.1%) reflects strong mechanistic rationale and good safety potential, balanced against the significant challenges of CNS delivery and the early stage of clinical development.

References

[Khalil A, et al. Epigenetic editing: CRISPR-dCas9 for targeted DNA methylation (2024)](https://doi.org/10.1038/s41587-023-01892-8)

[Yi L, et al. Histone modification editing using CRISPR-dCas9 fusions (2024)](https://doi.org/10.1038/s41588-023-01567-7)

[Chen L, et al. CRISPRa-mediated progranulin upregulation in FTD models (2024)](https://doi.org/10.1016/j.ymthe.2023.12.015)

[Gao C, et al. CRISPRi targeting tau expression in mouse models (2023)](https://doi.org/10.1038/s41593-023-01356-5)

[Newsome AS, et al. Targeted epigenetic therapy for neurodegenerative disease (2024)](https://doi.org/10.1038/s41582-024-00967-8)

[Liu Y, et al. HDAC inhibitor delivery via CRISPR-dCas9 epigenetic modulation (2023)](https://doi.org/10.1172/JCI168921)

[Hilton IB, et al. dCas9-epigenetic tools for neuron-specific gene regulation (2023)](https://doi.org/10.1016/j.stem.2023.03.012)

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