A cell revealing its physiological state at any given moment is one thing. Cells that display their physiological history are separate. The information you share has more context than just temporal meaning. Multiple cells that record (and reveal) history can simultaneously complete a tissue-level version of Joe Gould’s oral history. But about what people talk to each other on sunny days and good days, and how they farm, quarrel, and go on pilgrimages. “
While Gould’s literary project was doomed, a somewhat similar cellular programming project by scientists at MIT looks very promising. We are guiding cells to engrave the history of their daily functions into long protein chains that can be imaged using . These functions include activation of genes and cellular pathways.
Boyden, Y. Eva Tan Neuroengineering Professor at MIT and a member of MIT’s McGovern Institute, said: Koch Institute for Brain Research and Integrative Cancer Research. It’s this kind of tracking that MIT scientists hope to achieve with reprogramming technology.
This technique can be used to reveal steps underlying processes such as memory formation, response to drug therapy, and gene expression. If this technology can be made to work over a sufficiently long period of time, it could even shed light on processes such as aging and disease progression.
Details of the technique that appears in nature biotechnology, in a paper entitled “Recording Cell Physiological History Along Optically Readable Self-Assembling Protein Chains.” (His Boyden is the senior author of this paper. The lead author is his Changyang Linghu, PhD, a former J. Douglas Tan postdoctoral fellow at the McGovern Institute and now an assistant professor at the University of Michigan.)
“Here, we describe an expression recording island, a fully genetic spheroid that enables both continuous digital recording of biological information in cells and subsequent high-throughput readout in fixed cells. It’s a coded approach, ”writes the article’s author. “Information is stored in growing intracellular protein chains composed of self-assembling subunits, which are human-designed filament formations, each with different epitope tags corresponding to different cellular states or functions. It is a protein (e.g., gene expression downstream of neuronal activity or pharmacology), which allows us to read the physiological history along the ordered subunits of the protein chain using conventional light microscopy. ”
“Recording Islands” represent a new way to study biological systems such as organs. These systems contain many different types of cells, all of which have unique functions. To study these systems, scientists typically rely on methods to image proteins, RNA, or other molecules within cells. These methods can provide hints about what the cells are doing. However, most of these methods only allow him to glimpse a single moment in time or do not work well with very large cell populations.
“Biological systems are often composed of many different types of cells. For example, the human brain has 86 billion cells,” Linghu points out. “To understand this kind of biological system, we need to observe physiological events in these large cell populations over time.”
In the current study, researchers chose epitope tags called HA and V5. Each of these tags can be conjugated to a different fluorescent antibody, making it easier to later visualize the tags and determine the sequence of the protein subunits.
Generation of V5-containing subunits is dependent on activation of a gene called c-fos, which is involved in encoding new memories. HA-tagged subunits make up the bulk of the chain, but whenever the V5 tag appears in the chain, it means that c-fos was activated during that time.
“We hope to use this kind of self-assembly of proteins to record the activity of all cells,” Linghu said. “It’s not only a snapshot of time, it’s also a record of past history, just as tree rings can permanently store information over time as wood grows.” .”
The researchers used the system to record c-fos activation in neurons growing in experimental dishes. The c-fos gene was activated by chemically induced neuronal activation and the V5 subunit was added to the protein chain.
To test whether this approach works in animal brains, the researchers programmed mouse brain cells to produce protein chains when the animals were exposed to certain drugs. The researchers were then able to detect the exposure by preserving the tissue and analyzing it with a light microscope.
Researchers designed the system to be modular, allowing different epitope tags to be exchanged and different types of cellular events to be detected. This, in principle, involves cell division and the activation of enzymes called protein kinases that help regulate many cellular pathways. .
Researchers also hope to extend the record duration that can be achieved. In this study, they recorded events for several days before imaging the tissue. Since protein chain length is limited by cell size, there is a trade-off between the time that can be recorded and temporal resolution, or frequency of event recording.
“The total amount of information that can be stored is fixed, but in principle you can slow down or speed up the growth of the chain,” Linghu argued. , synthesis can be slowed down to reach cell size in less than two weeks.
Researchers are also working on designing the system so that it can record multiple types of events in the same chain by increasing the number of different subunits that can be incorporated.