A team of genome engineers has triggered a record-breaking 13,200 genetic changes to a single human cell. The team is led by Harvard University professor George Church who broke the previous record for bulk edits made to a single cell in 2017 when his team produced 62 copies of a retrovirus found in pig genomes.
To set the new record, the researchers aimed CRISPR at a type of DNA sequence called a LINE-1. This is a strange repetitive element able to copy itself and found across 17% of the human genome.
CRISPR cuts open the double helix so therefore making too many edits at once will kill a cell. To bypass that issue, the Harvard team utilized a modified version of CRISPR known as a base editor.
Instead of cutting DNA, the base editor replaces genetic letters. This removed the damaging effects to the double helix, allowing the researchers to edit thousands of genes without killing off the cell. In fact, they were able to make over 13,000 changes at once.
What may be the purpose of such work?
"Church says his eventual objective is to create supplies of human organs or tissues whose genomes are revised so they are immune to all viruses. That process, called recoding, would involve about 9,811 precise genetic modifications, according to the team. Church says the lab has started the process of recoding supplies of his own cells in the lab. “These are intended to be safe...and universal stem cells,” he says," wrote Antonio Regalado for MIT Technology Review
But that is not all. Church told New Scientist he hopes in the future to "knock-out 100 percent of active LINE elements.”
If so, he may already be halfway there. The 13,200 currently achieved edits account for about half of the 26,000 active LINE-1 transposons in a human cell.