Integrative transcriptomic and cistromic analyses reveal endothelial mechanotransduction–clock coupling and TEAD-dependent regulation of CRY1 and CLOCK in pulmonary arterial hypertension
This study integrates multi-omics analyses and experimental validation to demonstrate that in pulmonary arterial hypertension, endothelial mechanotransduction drives the upregulation of circadian clock genes CRY1 and CLOCK through a TEAD-dependent YAP/TAZ signaling axis.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Inside the body's vast network of blood vessels, the walls of the arteries are constantly feeling the pressure of blood flowing past them. This physical force is not just a mechanical push; it is a signal that cells use to understand their environment and decide how to behave. In a healthy state, these signals help maintain the vessel's shape and function. However, in a severe condition called pulmonary arterial hypertension, the small arteries in the lungs become stiff and narrow, forcing the heart to work much harder to pump blood. This disease is driven by a complex remodeling of the vessel walls, where the cells lining the arteries change their behavior, often growing too much or failing to relax. For a long time, scientists have known that mechanical forces play a central role in this process, but the specific molecular instructions that tell these cells how to react to that pressure have remained unclear.
At the same time, nearly every cell in the human body runs on an internal clock. This circadian rhythm is a biological timer that regulates when genes turn on and off, influencing everything from metabolism to cell repair. In the lungs, this clock helps keep the blood vessels healthy and responsive. The big question researchers have been trying to answer is whether the physical pressure felt by the lung arteries is connected to this internal timekeeping system. Do the mechanical forces that drive the disease also hijack the cell's clock? If they do, understanding that link could reveal new ways to treat the condition.
A team of researchers set out to solve this puzzle by combining massive amounts of existing genetic data with new experiments in the lab. They began by looking at the genetic blueprints from the lungs of patients with pulmonary arterial hypertension. By analyzing data from hundreds of patients across different studies, they searched for patterns that linked the activity of genes involved in sensing mechanical force with genes that control the circadian clock. They found a clear connection: in the lung tissue of patients with the disease, the genes that respond to physical stress and the genes that keep time were moving in sync. When the mechanical stress signals were high, the clock-related signals were also high. This suggested that the two systems were coupled, working together rather than independently.
To understand exactly which cells were responsible for this connection, the researchers zoomed in on the data, looking at individual cell types rather than just the whole lung tissue. They discovered that this synchronized behavior was most strongly present in the endothelial cells, the thin layer of cells that line the inside of the blood vessels. In these specific cells, the link between feeling pressure and keeping time was robust. However, the story was not the same for every cell type. In other cells within the lung, such as the smooth muscle cells that form the vessel wall, the relationship was different, sometimes even showing the opposite pattern. This finding was crucial because it showed that the disease process is not uniform; the way cells react to stress depends heavily on what kind of cell they are and where they are located in the lung.
The researchers then wanted to know how this connection actually worked. They focused on a specific pair of proteins, YAP and TAZ, which are known to act as the cell's primary sensors for mechanical stress. When the vessel wall gets stiff, these proteins move into the cell's nucleus and team up with a partner protein called TEAD to turn on specific genes. The team hypothesized that this YAP-TEAD team might be the one turning on the clock genes. To test this, they used human cells from the umbilical vein and the pulmonary artery in the lab. They engineered these cells to have a permanently active version of the YAP and TAZ proteins, mimicking the constant stress seen in the disease.
The results confirmed their hypothesis. When the YAP and TAZ proteins were active, the cells produced significantly more of two key clock proteins, CRY1 and CLOCK. But the researchers went a step further to prove that this was not just a coincidence. They created mutant versions of the YAP and TAZ proteins that could no longer bind to their partner, TEAD. When they activated these mutant proteins, the increase in the clock genes disappeared. This proved that the mechanical stress signal had to pass through the TEAD protein to reach the clock genes. It was a direct line of communication: physical pressure activates YAP and TAZ, which then use TEAD to switch on the clock machinery.
To make sure this mechanism was real and not just a pattern in the data, the researchers looked at the physical structure of the DNA in the cells. They found that the YAP, TAZ, and TEAD proteins were all sitting right next to the genes for CRY1 and CLOCK, physically occupying the same spots on the DNA strand. This provided the final piece of evidence, showing that these proteins were directly interacting with the genetic code to control the clock.
The study paints a detailed picture of how a physical force can rewrite the genetic instructions of a cell. In the lungs of patients with pulmonary arterial hypertension, the constant pressure on the blood vessels triggers a chain reaction that starts with mechanical sensors and ends with the cell's internal clock. This coupling is most prominent in the cells lining the blood vessels, suggesting that the disease process is deeply rooted in how these specific cells interpret their environment. While the researchers did not test new drugs or propose immediate treatments, their work identifies a specific molecular pathway that links the physical world of blood pressure to the biological world of timekeeping. By pinpointing the YAP-TEAD-CRY1-CLOCK axis, they have provided a clear target for future research, offering a new way to think about how mechanical stress drives disease and how it might be stopped.
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