If you hear the name The Vault Guy, you would probably think of someone who listens to ‘clicks’ while rotating the dial on a vault’s lock during a break-in. Outside of YouTube, he is Leonard Rome, cell biologist at the University of California, Los Angeles. His discovery is the cornerstone of TimeVaults, a time capsule created by researchers to collect and preserve mementos of the past.
Just as history provides insight and plausible predictions of what may happen in the future, a cell’s past has direct implications for its future, and recording those events can unravel the secrets of stem-cell biology and cancer drug resistance. TimeVaults are engineered cellular storage units developed from barrel-shaped cellular structures known as vaults, the latter discovered in the 1980s by Leonard Rome, aka The Vault Guy.
“This is a major step towards a long-standing goal in the field: being able to continuously record transcription in human cells,” says Randall Platt, a biological engineer at the Swiss Federal Institute of Technology (ETH) in Zurich. “I anticipate that TimeVaults will allow us to observe facets of biology previously inaccessible to us.”
TimeVaults store the molecular products of gene transcription, called messenger RNA (mRNA), which are produced from DNA after it is transcribed. A cell undergoes a vast number of changes, dynamic throughout. mRNA is commonly used to track changes within a cell, providing a snapshot of the cell at a given point in time, typically at the end of an experiment. The mRNA molecules are measured by sequencing and are compared to their levels in other cells to reconstruct a cell’s past experiences.
Scientists also track specific molecules using a fluorescent dye and a microscope. This method limits the number of processes that can be monitored simultaneously. CRISPR-based cell recorders are also used. Using CRISPR gene editing, the scientists create a non-removable genetic ledger of transient events within the cell, such as the activity of a specific molecular pathway over time. The ledger can then be read by genomic sequencing to identify edits at a later time, effectively reconstructing a cell’s past.
These methods are all lucrative, but with one downside: the researchers need to decide which events they would like to work with, creating a frame-bound field of observation. Fei Chen’s team has found the solution to this problem. To find an unbiased solution, Chen turned to YouTube, delving into structures called vaults within mammalian cells, discovered by Rome. To turn the vaults into time capsules, Chen’s team mutated a vault protein so it began to recognize and bind a molecular hallmark of mRNA molecules, hence capturing the mRNA inside the vault. This protein is the ‘record’ button— it is triggered by administering a drug to the cells and stopped by withdrawing the drug.
With these modifications, a mere cell organelle became a treasury of information— the TimeVault. This modified cell structure captured mRNA molecules produced over 24 hours in a human cell line and retained them for at least a week. No changes were observed in cells with TimeVaults instead of their regular versions, nor did the barrel-shaped vaults change their sizes due to their cargo.
Chen’s team has now focused on using TimeVaults to crack the code by which xrug-evading cancer cells, called persister cells, safeguard themselves from drugs. The research involves many other factors, the major being major changes in transcription that can overshadow the transcriptional changes that give these cells their characteristic drug-evading capacity.
Using TimeVaults, Chen found hundreds of genes that were overactive in persister lung cancer cells. Subduing some of the highly expressed genes made the cells more vulnerable to cancer drugs, killing many of them. Chen is also using TimeVaults to study how stem cells differentiate into various cell types.
This method is seen as complementary to CRISPR-based methods, with research underway to see if proteins or other cell mementos can be stored inside TimeVaults. Many scientists are eager to work with TimeVaults, one being Theresa Loveless, a synthetic biologist at Rice University in Houston. She ran into problems using CRISPR-based methods to work on persister cells. Now she has just the proper apparatus to fight these notorious cancer cells.
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