Cells got rhythm: signal timing determines cell type balance in the gut

Deep in the lining of the small intestine, cells are talking to each other in a language scientists are only now beginning to decode. But unlike most conversations, what matters here is not just what is said — it is how often it is repeated. In a study published in the journal Science, researchers at the Hubrecht Institute in the Netherlands report that the rhythm of a chemical signal oscillating inside gut cells helps determine which types of cells the intestine produces. When the team experimentally changed the frequency of these oscillations, the balance of cell types shifted in response. The discovery reveals a previously underappreciated way in which tissues may control their composition, and it offers a new lens for understanding how disrupted signaling dynamics contribute to inflammation and cancer.

The intestine is one of the busiest construction sites in the human body. Its lining renews itself every five to seven days, one of the highest cell turnover rates found anywhere in the body. Stem cells embedded in the intestinal lining churn out these replacement cells, which then take on specialized roles: some absorb nutrients, others secrete protective mucus, and still others coordinate the gut’s immune defenses. To keep the intestine healthy, the body must carefully control how many cells of each type it produces. Too many or too few of any one kind can tip the delicate balance that keeps this rapidly renewing tissue functioning properly.

Cells coordinate this process by communicating through chemical signals. When a target cell detects a signaling molecule, it sets off a chain of events inside the cell known as a cell signaling pathway, which helps the cell determine how to respond. Crucially, the activity of signaling molecules does not simply switch on and stay on. It can rise and fall in waves, a phenomenon called oscillation. The Sonnen group at the Hubrecht Institute, led by senior group leader Ina Sonnen, suspected that these waves might carry more information than biologists had appreciated. Their hunch led them to examine the dynamics of a specific signal in the gut in unprecedented detail.

“We found that cells not only respond to whether a signal is present or absent, but also to how often this oscillation repeats within a certain time,” says Sonnen. “This means that this oscillation frequency carries additional information. It’s a bit like FM radio, where audio information is encoded by changes in the frequency of a radio signal.” The analogy is a precise one. In frequency modulation, the information is not in the strength of the signal but in how its timing changes. The researchers proposed that gut cells might similarly read the frequency of an oscillating signal to guide their decisions about what kind of cell to become.

The signal the team studied is called Hes1, a protein that helps control what types of cells are produced by intestinal stem cells. Working in collaboration with the van Rheenen group at the Netherlands Cancer Institute, the researchers used fluorescence to track the amount of Hes1 protein in cells of the mouse gut over time. They found that Hes1 levels oscillate. The study was led by three shared first authors from the Sonnen group: Sonja Weterings, Hiromune Eto and Jan-Daniël de Leede-Scheven. To analyze the oscillations in detail, the team turned to intestinal organoids — tiny structures of cells that resemble miniature versions of an organ, grown in the laboratory from real gut tissue.

“We first noticed that the oscillations became slower as cells moved away from the stem cell region,” says Weterings. “That made us wonder whether these different rhythms might have a biological function.” The observation raised an intriguing question: if the rhythm of the signal changes systematically across the tissue, does the timing itself carry meaning? “We also found that different cell types showed different Hes1 rhythms: some cell types had faster oscillations than others,” adds Eto. “This suggested that the frequency of the oscillations might be linked to the decision-making of stem cells. In other words, differences in the Hes1 rhythm might influence which type of cell an intestinal stem cell becomes.”

To test this idea directly, the researchers experimentally changed the timing of the Hes1 rhythms in their organoids. The production of Hes1 is induced by a signaling pathway called Notch signaling, a conserved pathway with important roles in development and tissue maintenance. To temporarily switch this pathway off at precise intervals, the team used a microfluidic system — a laboratory setup that can deliver tiny, precisely timed pulses of chemicals to living cells. “We delivered small amounts of a ‘brake’ chemical to the organoids at precise intervals,” explains Weterings. “By timing the chemical pulses, we shifted the frequency of Hes1 oscillations to match the frequency we provided experimentally. This meant we could speed up or slow down the oscillations and see what happened to the organoids.”

Because organoids actively produce diverse cell types, just like a real gut, the team could assess how experimentally changing the frequency of Hes1 oscillations affected the composition of the tissue. They carried out this work in collaboration with the van Oudenaarden group at the Hubrecht Institute. “We saw that specific frequencies clearly changed the balance of different cell types produced by the organoids,” says de Leede-Scheven. “This showed us that the frequency of the oscillations can actually influence which cell types are produced.” The result demonstrates that the timing of a signal — not merely its presence or strength — can carry information that helps determine what a cell will become. It reveals a previously underappreciated mechanism by which tissues may control their cell-type composition.

The implications extend well beyond the gut. “Signaling pathways are conserved across different tissues but have different functions,” concludes Sonnen. “Altering the frequency of these oscillating signals is probably an important mechanism for many of them.” Because the same signaling pathways operate in tissues throughout the body, frequency encoding may be a widespread strategy for regulating cell type balance in development and tissue homeostasis. The Sonnen group studies how biological information is robustly transmitted via signaling pathway dynamics in multicellular systems, using mouse somitogenesis as a model during development and intestinal organoids during tissue maintenance. They have established microfluidic tools to dynamically modulate intercellular signaling and complement them with biochemical and cell biological techniques to unravel the mechanism of dynamic signal encoding at the molecular level.

The findings may improve understanding of how the intestines and other tissues maintain a healthy balance of cell types, and they open a new avenue for investigating disease. When the rhythm of signaling goes awry, the carefully tuned balance of cell types can collapse — a hallmark of conditions such as inflammation and cancer. By showing that signal frequency actively shapes tissue composition, the Hubrecht team has provided researchers with both a concept and a set of experimental tools to probe how disrupted signaling dynamics contribute to disease. The study, published in Science under the title “Frequency encoding regulates cell type composition in the small intestine,” suggests that to understand how tissues stay healthy, scientists may need to listen not just to what cells say, but to the rhythm at which they say it.

Subject of Research: Cell signaling dynamics in the small intestine

Article Title: Cells got rhythm: signal timing determines cell type balance in the gut

Article References: Cells got rhythm: signal timing determines cell type balance in the gut. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Cells, rhythm, signal, timing, determines, cell, type, balance, scientific research