Researchers Improve Gene Editing Efficiency and Applications

Scientists from the department of Developmental Biology / Physiology at the Centre for Organismal Studies of Heidelberg University have made a significant breakthrough in genome editing. The team, led by Professor Dr. Joachim Wittbrodt, has succeeded in substantially improving the efficiency of molecular genetic methods, such as CRISPR/Cas9 and related systems, and in broadening their areas of application.

The team fine-tuned these tools to enable effective genetic screening to model specific gene mutations and modify initially inaccessible DNA sequences. This opens new areas of work in basic research and, potentially, therapeutic applications. The team's "VIP admission ticket," or "hei-tag," allows enzymes equipped with it into the nucleus quickly, enabling highly efficient, targeted genome alterations in the model organism medaka, the Japanese ricefish (Oryzias latipes), mammalian cell cultures, and mouse embryos.

A significant challenge when using CRISPR/Cas9 is the efficient delivery of Cas9 enzymes to the nucleus. "The cell has an elaborate 'bouncer' mechanism. It distinguishes between proteins that are allowed to translocate into the nucleus and those that are supposed to stay in the cytoplasm," explains Dr. Tinatini Tavhelidse-Suck from Professor Wittbrodt's team. Access is enabled by a tag made up of a few amino acids that functions like an "admission ticket." The scientists have now come up with a generally valid "VIP admission ticket" that lets enzymes equipped with it into the nucleus very quickly.

In a further study, the Heidelberg scientists showed that base editors operate highly efficiently in the living organism and are even suited to genetic screening. In an experiment with Japanese rice fish, they were able to show that these locally limited, targeted modifications in individual building blocks of the DNA achieve an outcome that is otherwise only obtained by the comparatively laborious breeding of organisms with altered genes.

The research team at COS, in cooperation with Dr. Jakob Gierten, a pediatric cardiologist at Heidelberg University Hospital, focused on specific genetic mutations. These mutations were suspected of triggering congenital heart defects in humans.

By modifying individual building blocks of the DNA of the model organism's relevant genes, the scientists could imitate and study fish embryos with the described heart defects. The targeted intervention led to visible changes in the heart during the early stages of fish embryonic development, enabling the researchers to confirm the initial suspicion and deepen their understanding of the underlying mechanisms. This discovery has the potential to help create new therapies for congenital heart defects in humans, and the team's work has opened a new chapter in the field of genome editing.