The ability to observe the expression of multiple genes in tandem would be a powerful tool for scientists to utilize, yet they have been limited to studying single or very small numbers of genes at any one time. However, a new approach developed by Harvard geneticist George Church, Ph.D., professor of genetics at Harvard Medical School, of Health Sciences and Technology at Harvard and MIT, and senior author on the current study, is set to assist researchers explore how tandem gene circuits direct cellular processes, such as tissue development or stem cell differentiation.
The findings from this study were published online recently in Nature Methods through an article entitled “Highly efficient Cas9-mediated transcriptional programming”.
Dr. Church and his team employed the activity of the Cas9 protein, which has often been dubbed the Swiss Army knife of gene editing. In this novel approach the investigators “reprogrammed” Cas9 to activate transcription of the genes that it binds to rather than cleaving them, which is its normal function. Moreover, the team was able to engineer Cas9 as a fusion protein to a triple-pronged transcription factor, thereby obtaining robust gene expression.
“In terms of genetic engineering, the more knobs you can twist to exert control over the expression of genetic traits, the better,” said Dr. Church. “This new work represents a major, entirely new class of knobs that we could use to control multiple genes and therefore influence whether or not specific genetic traits are expressed and to what extent—we could essentially dial gene expression up or down with great precision.”
Dr. Church and his team are excited about the implications of being able to precisely manipulate gene expression and feel some of the greatest impact could be in the areas of organ transplant and regenerative therapies.
“We envision using this approach to investigate and create comprehensive libraries that document which gene circuits control a wide range of gene expression,” said Alejandro Chavez, Ph.D., postdoctoral fellow at the Wyss Institute and lead author on the study.
Dr. Chavez also noted that the new approach could help researchers study the so called DNA “dark matter”, which are genes not directly involved in transcription that comprise huge sections of the genome. The re-engineered Cas9 could bind to the dark matter regions, turning the gene circuits on and seeing which exert influence over gene expression.
Additionally, the ability to manipulate multiple genes in tandem so precisely has sweeping implications in stem cell engineering. “In order to grow organs from stem cells, our understanding of developmental biology needs to increase rapidly,” explained Dr. Church. “This multivariate approach allows us to quickly churn through and analyze large numbers of gene combinations to identify developmental pathways much faster than has been previously capable.”
This new approach also has the capacity to be used in combination with other gene-editing technologies currently applied by molecular biologists. The applications are seemingly limitless, and Dr. Church’s team is currently exploring a multitude of scenarios where they believe the technique will be of most value.
“This newest tool in the Cas9 genome-engineering arsenal offers a powerful new way to control cell and tissue function that could revolutionize virtually all areas of science and medicine, ranging from gene therapy to regenerative medicine and anti-aging,” said Donald Ingber, M.D., Ph.D., Wyss Institute founding director.