Why Many Cells Are Better Than One

Researchers from Johns Hopkins have quantified the number of possible decisions that an individual cell can make after receiving a cue from its environment, and surprisingly, it's only two. The first-of-its-kind study combines live-cell experiments and math to convert the inner workings of the cell decision-making process into a universal mathematical language, allowing information processing in cells to be compared with the computing power of machines.

The research, published Sept. 15 in the journal Science, also demonstrates why it's advantageous for cells to cooperate to overcome their meager individual decision-making abilities by forming multicellular organisms.

"Each cell interprets a signal from the environment in a different way, but if many cells join together, forming a common response, the result can eliminate the differences in the signal interpretation while emphasizing the common response features," says Andre Levchenko, Ph.D., associate professor of biomedical engineering and member of the Institute for Cell Engineering. "If a single blood vessel cell gets a signal to contract, it is meaningless since all the surrounding cells in the blood vessel need to get the message to narrow the blood vessel. Cell collaboration does wonders in terms of their ability to transfer information and convert it into decision-making."

One bit of information represents two choices: yes or no, on or off, or one or zero in binary code, used by computer programmers. Two bits doubles the amount of choices to four and so on for each bit added.

To determine how many bits of information a cell has for each decision, the researchers had to measure a real biological decision in progress. They decided to look at a well-known cell stimulant, a protein called tumor necrosis factor (TNF), responsible for turning on the inflammation response in the body. When cells detect TNF on their surface, they transmit a message that sends a messenger protein into the nucleus to turn on inflammation genes.