Broad and Whitehead Institute researchers have developed a promising epigenetic editing tool called CHARM in a significant advancement toward treating fatal familial insomnia and other prion diseases. This new approach aims to turn off disease-causing genes before they can produce harmful proteins, offering a potential solution for conditions that currently lack effective treatments.
Harnessing Epigenetic Mechanisms
The CHARM technology, short for Coupled Histone tail for Autoinhibition Release of Methyltransferase, utilizes the principles of epigenetic editing—a process that modifies gene expression without altering the DNA sequence itself. Unlike traditional gene editing that cuts DNA, epigenetic editing adds chemical tags to DNA, effectively silencing specific genes. This method, described in detail in the journal Science, represents a significant shift in how genetic diseases could be treated.
Sonia Vallabh, a Senior Group Leader at the Broad Institute who also suffers from a genetic mutation that causes prion disease, highlights the urgency and collaborative spirit that propelled this innovation. “The spirit of the collaboration since the beginning has been that there was no waiting on formality,” Vallabh remarks. “As soon as we realized our mutual excitement to do this, everything was off to the races.”
CRISPRoff to CHARM: The Evolution of Gene Silencing
The team initially used a precursor technology, CRISPRoff, which employs the CRISPR-associated protein Cas9 to direct methylation efforts to silence genes. However, its large size and potential for triggering immune responses posed significant challenges for clinical application, particularly in brain therapies.
To overcome these hurdles, the researchers, led by Edwin Neumann and Tessa Bertozzi, engineered a smaller and more efficient variant. They replaced Cas9 with zinc finger proteins (ZFPs), which are smaller and less likely to elicit an immune response. This adjustment made the delivery of the genetic material via adeno-associated viruses (AAVs) more feasible.
Advancements in Gene Delivery
Benjamin Deverman's research at the Broad Institute complements the development of CHARM by addressing gene delivery challenges. His team has engineered an AAV vector that can efficiently penetrate the
adult brain, a crucial step for treating neurodegenerative diseases. Published in Science, this finding enhances the potential for CHARMs to be used in clinical settings.
Future Prospects and Continuing Challenges
While CHARMs show promise in cell culture and animal models, demonstrating low toxicity and limited off-target effects, the path to clinical trials remains complex. The team is now focused on refining the technology to enhance its efficacy, safety, and manufacturability for potential therapeutic use.
Jonathan Weissman, a professor at MIT and a pivotal figure in the development of CHARM, notes the strategic collaboration that accelerated their progress. “With the Whitehead and Broad Institutes right next door to each other, I don’t think there’s any better place than this for a group of motivated people to move quickly and flexibly in the pursuit of academic science and medical technology,” he says.
Publication Details
Edwin N. Neumann et al., Brainwide silencing of prion protein by AAV-mediated delivery of an engineered compact epigenetic editor. Science 384, ado7082 (2024). DOI 10.1126/science.ado7082
Harnessing Epigenetic Mechanisms
The CHARM technology, short for Coupled Histone tail for Autoinhibition Release of Methyltransferase, utilizes the principles of epigenetic editing—a process that modifies gene expression without altering the DNA sequence itself. Unlike traditional gene editing that cuts DNA, epigenetic editing adds chemical tags to DNA, effectively silencing specific genes. This method, described in detail in the journal Science, represents a significant shift in how genetic diseases could be treated.
Sonia Vallabh, a Senior Group Leader at the Broad Institute who also suffers from a genetic mutation that causes prion disease, highlights the urgency and collaborative spirit that propelled this innovation. “The spirit of the collaboration since the beginning has been that there was no waiting on formality,” Vallabh remarks. “As soon as we realized our mutual excitement to do this, everything was off to the races.”
CRISPRoff to CHARM: The Evolution of Gene Silencing
The team initially used a precursor technology, CRISPRoff, which employs the CRISPR-associated protein Cas9 to direct methylation efforts to silence genes. However, its large size and potential for triggering immune responses posed significant challenges for clinical application, particularly in brain therapies.
To overcome these hurdles, the researchers, led by Edwin Neumann and Tessa Bertozzi, engineered a smaller and more efficient variant. They replaced Cas9 with zinc finger proteins (ZFPs), which are smaller and less likely to elicit an immune response. This adjustment made the delivery of the genetic material via adeno-associated viruses (AAVs) more feasible.
Advancements in Gene Delivery
Benjamin Deverman's research at the Broad Institute complements the development of CHARM by addressing gene delivery challenges. His team has engineered an AAV vector that can efficiently penetrate the
adult brain, a crucial step for treating neurodegenerative diseases. Published in Science, this finding enhances the potential for CHARMs to be used in clinical settings.
Future Prospects and Continuing Challenges
While CHARMs show promise in cell culture and animal models, demonstrating low toxicity and limited off-target effects, the path to clinical trials remains complex. The team is now focused on refining the technology to enhance its efficacy, safety, and manufacturability for potential therapeutic use.
Jonathan Weissman, a professor at MIT and a pivotal figure in the development of CHARM, notes the strategic collaboration that accelerated their progress. “With the Whitehead and Broad Institutes right next door to each other, I don’t think there’s any better place than this for a group of motivated people to move quickly and flexibly in the pursuit of academic science and medical technology,” he says.
Publication Details
Edwin N. Neumann et al., Brainwide silencing of prion protein by AAV-mediated delivery of an engineered compact epigenetic editor. Science 384, ado7082 (2024). DOI 10.1126/science.ado7082