Podcast Summary: The Peter Attia Drive #323 – CRISPR and the Future of Gene Editing with Feng Zhang, Ph.D.

Release Date: October 28, 2024

In Episode #323 of The Peter Attia Drive, host Dr. Peter Attia engages in a comprehensive conversation with Dr. Feng Zhang, a pioneering figure in the field of gene editing and a key contributor to the development of the CRISPR-Cas9 system. This episode delves deep into the scientific advancements, therapeutic potentials, and ethical considerations surrounding CRISPR technology. Below is a detailed summary capturing the essence of their discussion.

1. Introduction to Feng Zhang and His Background

Dr. Feng Zhang, a Professor of Neuroscience at MIT and an investigator at the Howard Hughes Medical Institute, shares his academic journey and contributions to neuroscience and gene editing.

• Education and Early Career:
  Dr. Zhang earned his Bachelor's degree in Chemistry and Physics from Harvard University, followed by a Ph.D. in Chemical and Biological Engineering at Stanford University. During his time at Stanford, he collaborated with Carl Deisseroth in developing optogenetics—a technique that allows precise control of neuronal activity using light.

• Transition to Gene Editing:
  Reflecting on his early work in optogenetics, Dr. Zhang identifies a significant bottleneck: the difficulty in inserting algal genes into specific genomic locations. This challenge pivoted his focus towards making gene editing more accessible and robust, leading to his extensive work with the CRISPR-Cas9 system.

2. The Origins and Mechanics of CRISPR-Cas9

Dr. Zhang provides an in-depth exploration of the CRISPR-Cas9 system, tracing its discovery and elucidating its role in bacterial immunity and gene editing.

• Discovery of CRISPR:
  Originally identified in the 1980s through the study of repetitive DNA sequences in E. coli, CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) systems were initially misunderstood. It wasn't until the early 2000s that research by scientists like Francisco Mojica highlighted the system's role in bacterial defense against viruses.

• Functionality of CRISPR-Cas9:
  The CRISPR-Cas9 system functions as an adaptive immune mechanism in bacteria. When a bacteriophage (a virus that infects bacteria) invades, CRISPR sequences capture snippets of the viral DNA, incorporating them into the bacterial genome. These sequences then guide the Cas9 enzyme to recognize and cleave the viral DNA upon subsequent infections, effectively neutralizing the threat.

  Dr. Feng Zhang [22:27]: "It's usually 30 letters long. And that is enough for the bacteria to uniquely recognize the virus."

• Cas Proteins and Their Roles:
  Various Cas (CRISPR-associated) proteins work in tandem with CRISPR RNA to target and eliminate viral genetic material. Cas9, the most widely used protein in gene editing, has revolutionized the ability to make precise modifications in the genome.

3. From Optogenetics to CRISPR: Bridging Neuroscience and Gene Editing

Dr. Zhang discusses how his work in optogenetics led to broader explorations in gene editing, emphasizing the transition from basic neuroscience tools to therapeutic applications.

• Limitations of Early Gene Insertion Techniques:
  Traditional methods of gene insertion lacked specificity, making it challenging to target precise genomic locations. This limitation was a significant hurdle in advancing optogenetics and other genetic therapies.

  Dr. Feng Zhang [06:14]: "The way that you would put a gene into the brain is usually by using a virus... by injecting the virus into a brain area that you want to study."

• The Promise of CRISPR in Neuroscience:
  Recognizing CRISPR's potential, Dr. Zhang and his team at MIT and the Broad Institute focused on harnessing this technology to overcome previous limitations, enabling more precise and efficient gene editing.

4. Gene Editing Technologies: CRISPR vs. Zinc Finger Nucleases and TALENs

A comparative analysis of existing gene editing technologies highlights why CRISPR-Cas9 emerged as the preferred tool.

• Zinc Finger Nucleases (ZFNs):
  ZFNs required intricate protein engineering to recognize specific DNA sequences, making them cumbersome and less efficient for widespread use.

  Dr. Feng Zhang [31:36]: "Nature has solved this problem by forming zinc finger arrays. So they tether multiple fingers together... to achieve specificity."

• Transcription Activator-Like Effector Nucleases (TALENs):
  TALENs offered improved programmability over ZFNs but still faced challenges in scalability and efficiency due to their repetitive protein structures.

• CRISPR-Cas9 Advantages:
  Unlike ZFNs and TALENs, CRISPR-Cas9 uses RNA guides to target DNA sequences, simplifying the process and enhancing versatility.

  Dr. Feng Zhang [05:34]: "It was resolution at the level of the word rather than the page."

5. Therapeutic Applications of CRISPR-Cas9

The conversation shifts to the practical implications of CRISPR technology in treating genetic diseases, highlighting current successes and ongoing challenges.

• Sickle Cell Anemia:
  CRISPR-based therapies involve editing bone marrow stem cells to correct the genetic mutation causing sickle cell disease. This approach aims for a one-time treatment that can potentially cure the disease.

  Dr. Feng Zhang [55:37]: "They will get the patient harvest their bone marrow cells and these cells are going to be modified in the laboratory where researchers will take the messenger RNA for Cas9."

• Huntington's Disease:
  Targeting the Huntington gene involves precisely deleting expanded repeat sequences to mitigate neurodegeneration. However, challenges include delivering CRISPR components efficiently to brain cells.

• Liver and Eye Diseases:
  The liver is amenable to CRISPR therapies using lipid nanoparticles for delivery, while ocular diseases like Leber's Congenital Amaurosis (LCA) have seen successful gene therapies such as Luxturna.

  Dr. Feng Zhang [83:10]: "The eye is the first place where in the US a gene therapy was developed and approved."

6. Delivery Mechanisms: Overcoming the Bottleneck

Effective delivery of CRISPR components to target cells remains a significant hurdle in therapeutic applications.

• Lipid Nanoparticles:
  These have shown high efficacy in delivering CRISPR-Cas9 to liver cells, achieving up to 90% delivery efficiency.

  Dr. Feng Zhang [87:19]: "In the liver is quite robust. You can probably get 80, 90% in."

• Viral Vectors:
  Adenoviruses are commonly used to deliver CRISPR components to specific tissues, though their large size poses packaging challenges.

• Future Directions:
  Developing smaller Cas proteins and enhancing delivery technologies are critical areas of ongoing research.

  Dr. Feng Zhang [75:12]: "We're working on engineering them. And there's a lot of good progress turning those systems into specific and comparably active systems as Cas9."

7. Ethical Considerations in Gene Editing

A central part of the discussion revolves around the ethical implications of germline gene editing versus somatic cell editing.

• The CRISPR Baby Controversy:
  Highlighting the 2018 incident where a scientist in China edited the embryos of twin girls to confer HIV resistance, Dr. Zhang discusses the global backlash and the necessity for ethical guidelines.

  Dr. Feng Zhang [97:07]: "I think there's a lot of discussion going on, so it's certainly not a settled issue."

• Therapeutic vs. Enhancement Applications:
  Dr. Zhang advocates for gene editing to treat severe genetic disorders while cautioning against modifications for non-therapeutic traits like intelligence or height.

  Dr. Feng Zhang [105:17]: "For diseases that can be clearly addressed with genetic editing, it's something that is definitely doable and I think it's okay to improve the lives of those patients."

• International Regulations:
  While the U.S. maintains restrictions on germline editing, international consensus remains fragmented, necessitating ongoing dialogue and policy development.

8. The Role of AI and Future Technologies

Dr. Zhang touches upon the intersection of artificial intelligence with gene editing, particularly in protein engineering and drug development.

• AI in Protein Design:
  Innovations like DeepMind's AlphaFold have revolutionized protein structure prediction, aiding in the design of more efficient and compact Cas proteins.

  Dr. Feng Zhang [65:57]: "AI is very powerful for protein engineering... they were able to use AI to look at all of them and learn from that large database to then come up with a prediction system called AlphaFold2."

9. Accelerating Scientific Research with CRISPR

The transformative impact of CRISPR on biomedical research is underscored by its ability to streamline the creation of transgenic animal models.

• Transgenic Mice:
  CRISPR enables the rapid generation of genetically modified mice by directly editing embryos, significantly reducing the time from years to months compared to traditional methods.

  Dr. Feng Zhang [68:49]: "With CRISPR or gene editing, you can get a mouse in two, three months."

10. Personal Journey and Optimism for the Future

Concluding the episode, Dr. Zhang reflects on his serendipitous journey into gene editing, emphasizing the importance of mentorship, education, and fostering curiosity in scientific endeavors.

• Inspiration and Mentorship:
  Recalling his early experiences with passionate teachers and hands-on experiments, Dr. Zhang highlights how these elements fueled his dedication to science.

• Optimism in Science:
  Despite challenges such as regulatory hurdles and societal skepticism, Dr. Zhang remains optimistic about the future of gene editing and its potential to revolutionize medicine.

  Dr. Feng Zhang [120:20]: "I'm an optimist. I think that's the only way to be... We're going to be accumulating new data for biology at an exponential pace."

Conclusion

Episode #323 of The Peter Attia Drive offers listeners an enlightening exploration of CRISPR technology through the expertise of Dr. Feng Zhang. From its bacterial origins to its profound implications in modern medicine, the conversation underscores both the transformative potential and the ethical complexities of gene editing. Dr. Zhang's insights not only illuminate the scientific advancements but also inspire a thoughtful consideration of the responsibilities that accompany such powerful technologies.

Notable Quotes:

• Dr. Feng Zhang [05:34]: "It was resolution at the level of the word rather than the page."

• Dr. Feng Zhang [22:27]: "It's usually 30 letters long. And that is enough for the bacteria to uniquely recognize the virus."

• Dr. Feng Zhang [65:57]: "AI is very powerful for protein engineering... they were able to use AI to look at all of them and learn from that large database to then come up with a prediction system called AlphaFold2."

• Dr. Feng Zhang [120:20]: "I'm an optimist. I think that's the only way to be... We're going to be accumulating new data for biology at an exponential pace."

This episode serves as a valuable resource for anyone interested in the cutting-edge developments of gene editing, offering both technical depth and ethical contemplation.