BioTech IP Review

Brainwide silencing of prion protein by AAV‑mediated delivery of an engineered compact epigenetic editor

  • Journal: Science
  • Publication Date: June 28, 2024
  • DOI: 10.1126/science.ado7082
  • Lead Authors: Edwin N. Neumann, Tessa M. Bertozzi, Elaine Wu, et al.
  • Institutions: Broad Institute of MIT and Harvard, Whitehead Institute, MIT, and collaborators.

What This Paper Covers

This study reports the development and in vivo application of a compact, AAV‑deliverable epigenetic editor designed to silence the prion protein gene (Prnp) across the entire brain — a long‑standing challenge in treating prion diseases such as Creutzfeldt‑Jakob disease, which are rapidly progressive and universally fatal once symptoms begin.

  • The researchers engineered a system called CHARM (“Coupled Histone tail for Autoinhibition Release of Methyltransferase”), which recruits the cell’s own DNA methylation machinery to a specific gene locus to stably silence gene expression. Unlike typical CRISPR gene editing, this method modifies epigenetics (gene activity) rather than cutting or altering the DNA sequence.
  • Efficient brainwide silencing of PrP: When delivered systemically via an adeno‑associated virus (AAV) vector capable of crossing the blood–brain barrier, the CHARM editor abolished expression of the prion protein throughout the mouse brain.
  • Reduced toxicity and improved delivery: The design minimizes transgene size and cytotoxicity — key barriers in delivering gene‑modifying systems to the brain.
  • Temporal control: The team also demonstrated strategies to control the duration of CHARM expression, which could reduce safety concerns associated with long‑term activity of editing tools in the brain.

Why This is Important

  • Therapeutic potential for prion diseases: Prion diseases currently have no effective treatments. Silencing the prion protein at its genetic source could halt disease progression if translated to humans, representing a paradigm shift in treating these fatal neurodegenerative disorders.
  • Epigenetic editing as a general platform: Beyond prion disease, this work demonstrates a versatile epigenetic editing platform that might be used to repress other harmful genes (e.g., toxic proteins in Alzheimer’s, Parkinson’s, Huntington’s, or other disorders) without permanently altering the DNA sequence.
  • Advances in in vivo delivery: Achieving widespread editing effects across the brain via systemic delivery is a major step toward feasible in vivo therapies for central nervous system targets.

Summary

This Science paper represents a landmark advance in epigenetic editing and therapeutic gene modulation — demonstrating, for the first time, efficient brainwide silencing of a disease‑causing gene using an engineered epigenetic editor delivered by viral vector. Its proof‑of‑concept may open new avenues for treating previously intractable neurodegenerative diseases.

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