Presented By: Biomedical Engineering
Biomedical Engineering Seminar Series
"Development of Genome Editing Approaches to Treat Cystic Fibrosis and Other Disorders," featuring Sriram Vaidyanathan, Ph.D.
Abstract:
Genetic disorders caused by mutations in essential genes are a significant burden on patients and the healthcare system. CRISPR-Cas9 technology allows us to precisely modify the genome. Gene insertion using Cas9 may restore the expression of these missing genes and treat genetic disorders. This restoration may be durable if achieved in long-lived tissue resident stem cells that give rise to different organs. However, efficient gene insertion in stem cells in vivo is a technical challenge that limits the development of durable therapies for genetic disorders. We aim to develop improved methods to insert genes in stem cells both ex-vivo and in vivo for the treatment of genetic disorders.
Our studies focus on replacing the CFTR gene that is involved in cystic fibrosis (CF). CF is a monogenic disorder that affects the lungs and many other organs. People with CF (pwCF) experience chronic infections that result in lung failure and death. Replacement of the CFTR gene in airway stem cells is thus likely to improve the survival of pwCF. However, this is challenging because it is a long gene (~4500 bp) that does not fit into adeno-associated virus (AAV) vectors that enable efficient gene insertion. Lipid nanoparticles (LNPs) packaged with Cas9 mRNA, sgRNA and single-stranded DNA (ssDNA) templates have been proposed as an alternative. ssDNA templates do not pose any size restriction theoretically. However, they are prone to degradation by nucleases even when the last few bases are protected by chemical modifications. Recent studies from our group have investigated if protection of internal bases within ssDNA templates may limit nuclease degradation further and improve gene insertion. Our studies show that the modification of internal bases improves gene correction by 2-3-fold in airway stem cells. The correction of CF-causing mutations using internal base modified templates restores CFTR function to 30-60% of the levels seen in non-CF controls. Our chemically modified ssDNA templates are effective when delivered using lipid nanoparticles and electroporation. Moreover, these templates are effective in other therapeutically relevant cells such as hematopoietic stem cells and T-cells. Ongoing studies are testing if these chemically modified ssDNA templates improve gene insertion in vivo. Apart from this study, our group is interested in alternative strategies to improve gene insertion through the modulation of DNA repair pathways and in developing improved methods to transplant genome engineered stem cells into the airways. Overall, these novel approaches to genome engineer stem cells may enable the development of durable therapies for devastating diseases such as CF.
Bio:
Sriram Vaidyanathan, PhD, is a principal investigator in the Center for Gene Therapy at the Abigail Wexner Research Institute at Nationwide Children’s Hospital and an assistant professor of Pediatrics at The Ohio State University College of Medicine. Dr. Vaidyanathan earned his bachelor’s degree in Biomedical Engineering from Purdue University and his PhD in Biomedical Engineering from the University of Michigan, Ann Arbor. He completed his postdoctoral training with Dr. Matthew Porteus at Stanford University, CA. His primary research interest has been the development of gene and cell therapies. His most recent work has been focused on the development of CRISPR/Cas9 based genome editing to treat cystic fibrosis (CF). His lab continues to further develop genome editing approaches to treat CF and other genetic diseases.
Zoom:
https://umich.zoom.us/j/94337625486
Genetic disorders caused by mutations in essential genes are a significant burden on patients and the healthcare system. CRISPR-Cas9 technology allows us to precisely modify the genome. Gene insertion using Cas9 may restore the expression of these missing genes and treat genetic disorders. This restoration may be durable if achieved in long-lived tissue resident stem cells that give rise to different organs. However, efficient gene insertion in stem cells in vivo is a technical challenge that limits the development of durable therapies for genetic disorders. We aim to develop improved methods to insert genes in stem cells both ex-vivo and in vivo for the treatment of genetic disorders.
Our studies focus on replacing the CFTR gene that is involved in cystic fibrosis (CF). CF is a monogenic disorder that affects the lungs and many other organs. People with CF (pwCF) experience chronic infections that result in lung failure and death. Replacement of the CFTR gene in airway stem cells is thus likely to improve the survival of pwCF. However, this is challenging because it is a long gene (~4500 bp) that does not fit into adeno-associated virus (AAV) vectors that enable efficient gene insertion. Lipid nanoparticles (LNPs) packaged with Cas9 mRNA, sgRNA and single-stranded DNA (ssDNA) templates have been proposed as an alternative. ssDNA templates do not pose any size restriction theoretically. However, they are prone to degradation by nucleases even when the last few bases are protected by chemical modifications. Recent studies from our group have investigated if protection of internal bases within ssDNA templates may limit nuclease degradation further and improve gene insertion. Our studies show that the modification of internal bases improves gene correction by 2-3-fold in airway stem cells. The correction of CF-causing mutations using internal base modified templates restores CFTR function to 30-60% of the levels seen in non-CF controls. Our chemically modified ssDNA templates are effective when delivered using lipid nanoparticles and electroporation. Moreover, these templates are effective in other therapeutically relevant cells such as hematopoietic stem cells and T-cells. Ongoing studies are testing if these chemically modified ssDNA templates improve gene insertion in vivo. Apart from this study, our group is interested in alternative strategies to improve gene insertion through the modulation of DNA repair pathways and in developing improved methods to transplant genome engineered stem cells into the airways. Overall, these novel approaches to genome engineer stem cells may enable the development of durable therapies for devastating diseases such as CF.
Bio:
Sriram Vaidyanathan, PhD, is a principal investigator in the Center for Gene Therapy at the Abigail Wexner Research Institute at Nationwide Children’s Hospital and an assistant professor of Pediatrics at The Ohio State University College of Medicine. Dr. Vaidyanathan earned his bachelor’s degree in Biomedical Engineering from Purdue University and his PhD in Biomedical Engineering from the University of Michigan, Ann Arbor. He completed his postdoctoral training with Dr. Matthew Porteus at Stanford University, CA. His primary research interest has been the development of gene and cell therapies. His most recent work has been focused on the development of CRISPR/Cas9 based genome editing to treat cystic fibrosis (CF). His lab continues to further develop genome editing approaches to treat CF and other genetic diseases.
Zoom:
https://umich.zoom.us/j/94337625486
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