RW DNA Record
Turning the cage into a "black box"
Maxim Rousseau, Polit.roo
Modern genome editing technologies make it possible to turn DNA molecules into a recording device similar to a "black box" in airplanes. It will register information about events occurring with the cell, tracking changes in gene expression and in external conditions.
Recently, one of these systems was proposed in a study published recently by the journal Science by Weixin Tang and David R. Liu, working at the Broad Institute and the Department of Chemistry and Biochemistry at Harvard University (Rewritable multi-event analog recording in bacterial and mammalian cells). When creating it, the now popular CRISPR-Cas9 technology was used. "Just as a flight recorder registers events that occur with an airplane, registration devices in a cage can be used to monitor stimuli to which it is exposed, or changes in signal transmission in the cage," says David Liu. For the system they created, the scientists chose the name CAMERA – CRISPR-mediated analog multi-event recording apparatus.
Recall that the CRISPR-Cas9 technology consists of a guide RNA that determines a given sequence of nucleotides in the DNA of a cell, as well as a Cas9 protein that cuts the DNA chain at a specified location. The CAMERA 1 system, created by Weixin Tang and David Liu, works in bacterial cells. It consists of plasmids (circular DNA molecules contained in a bacterial cell), in the sequence of nucleotides of which there is a signal for guiding RNA. Also, Cas9 protein is produced in these bacterial cells, but only in the presence of a specific antibiotic.
The researchers placed in bacterial cells both those plasmids in which there was a signal for the CRISPR-Cas9 system, and ordinary unmodified plasmids. The ratio of the two types of plasmids was measured. After that, it was possible to influence the cells with the chosen antibiotic. It caused activation of the Cas9 protein, and it began to destroy the modified plasmids. The ratio of plasmids in the cell varied. By the magnitude of this change, it is possible to determine the amount of antibiotic added to the medium and the duration of its effect on bacterial cells. So plasmids floating in the cytoplasm turned into a carrier of information. Moreover, Weixin Tang and David Liu learned how to "reset the counter" and use the same set of plasmids to register subsequent effects on the cell.
The second system of the same authors (CAMERA 2) was based on the modified CRISPR-Cas9 technology, which allows, without cutting the DNA molecule, to replace a specific nucleotide in it at the specified location. For example, cytosine for thymine or adenine for guanine. Such a modified DNA editing technology was developed in the laboratory of David Liu last year.
Using the CAMERA 2 system, you can record up to four types of events that occur with a cell, including exposure to light and the penetration of viruses, and the recording reflects the chronological order of these events. Of particular interest is the possibility demonstrated in the study of recording the work of the Wnt signaling pathway, which is associated with the regulation of cell differentiation and embryonic development. The modified CAMERA 2 system no longer works in bacterial cells, but in mammalian cells. For reliable reading of information, only a dozen to a hundred cells with built-in recorders are enough.
So far, such "cellular recorders" are rather ingenious engineering solutions, but it is already clear that there are prospects for their practical application. For example, the team of biologist Harris Wang from Columbia University Medical Center intends to use such recorders in the study of human gut bacteria. And Jan Philipp Junker and his colleagues from the Max Delbruck Center for Molecular Medicine in Berlin are working on a registrar that will trace the development of individual cells of the body (in experiments on danio rerio fish).
Portal "Eternal youth" http://vechnayamolodost.ru