Scientists from the Hubrecht Institute discover backdoor into the cell – implications for the treatment of genetic diseases

Scientist at the Hubrecht Institute have developed a revolutionary and effective method of introducing molecular tools into cells. According to Prof. Niels Geijsen, who headed the research team, this discovery brings us one step closer to treating genetic diseases, “The difficulty of treating genetic (inherited) diseases is that we, thus far, are unable to safely transport large therapeutic compounds, for example, proteins, into cells,” explains Geijsen. “ With our new technology, we’ve found that we can do this very efficiently.” The researchers published their method this week in the scientific journal, Cell.

Proteins are the workhorses of our cells as they coordinate nearly all biochemical processes in our body with great precision. The administration of specific gene-editing proteins into patient (stem)cells would be an effective method for the treatment of hereditary diseases, however, the cell membrane forms an impenetrable barrier that prevents administered proteins from passing through. Prof. Geijsen and his team have developed a novel technology that makes it possible to introduce proteins very efficiently into almost every cell type in the human body, “Now that we’ve developed this technology,” adds Geijsen, “we want to investigate how it can be applied to repair disfunctional genes in patient cells.”

The technology, called iTOP, activates a back door in a cell, whereby proteins or RNA are taken up from the cell’s surroundings and inserted into the cell. 

Table salt
Geijsen originally planned to use a cellular pathway that allows toxic proteins of certain bacteria to enter the cell. He hoped that other proteins could be introduced in a similar manner, by linking them to a small, harmless part of the toxin. After nearly a year, the system finally worked. Surprisingly, the team discovered that the toxin part was not necessary for the protein transport. Instead, they had uncovered a combination of compounds which forces the cell to take up any protein it’s offered. The main ingredient was sodium chloride, commonly known as table salt. The administered salt mixture extracts water from a cell, which activates a process called “macropinocytosis”; literally “drinking large mouthfuls of liquid”. Proteins dissolved in the salt mixture are engulfed by the thirsty cells. A second substance in the mixture then causes the release of the proteins inside the cell, where they can do their job. 

CRISPR / Cas9
What makes iTOP so spectacular is that it combines extremely well with the recently discovered CRISPR / Cas9 gene-editing system. The CRISPR / Cas9 system makes it possible to modify a specific DNA sequence in the genome, yet, it has been very difficult to introduce this system efficiently and safely into cells. Geijsen and his team may have found the critical link that can drive CRISPR / Cas9 into the clinic, since iTOP is highly efficient and does not rely on a viral vector.