Â鶹ÒùÔº

Researchers have captured the first clear view of the hidden architecture that helps shape a simple multicellular organism, showing how cells work together to build complex life forms.

In a study in the Proceedings of the National Academy of Sciences, a team of British and German scientists revealed the structure of the extracellular matrix in Volvox carteri, a type of green algae that is often used to study how multicellular organisms evolved from single-celled ancestors.

The extracellular matrix (ECM) is a scaffold-like material that surrounds cells, providing physical support, influencing shape, and playing an important role in development and signaling. Found in animals, plants, fungi and algae, it also played a vital part in the transition from unicellular to multicellular life.

Because the ECM exists outside the cells that produce it, scientists believe it forms through self-assembly: a process still not fully understood, even in the simplest organisms.

To investigate, researchers at the University of Bielefeld genetically engineered a strain of Volvox in which a key ECM protein called pherophorin II was made fluorescent so the matrix's structure could be clearly seen under a microscope.

What they saw was an intricate foam-like network of rounded compartments that wrapped around each of Volvox's roughly 2,000 somatic, or non-reproductive, cells.

Working with mathematicians at the University of Cambridge, the team used machine learning to quantify the geometry of these compartments. The data revealed a stochastic, or randomly influenced, growth pattern that shares similarities with the way foams expand when hydrated.

These shapes followed a statistical pattern that also appears in materials like grains and emulsions, and in biological tissues. The findings suggest that while individual cells produce ECM proteins at uneven rates, the overall organism maintains a regular, spherical form.

That coexistence—between noisy behavior at the level of single cells and precise geometry at the level of the whole organism—raises new questions about how multicellular life manages to build reliable forms from unreliable parts.

"Our results provide quantitative information relating to a fundamental question in developmental biology: how do cells make structures external to themselves in a robust and accurate manner," said Professor Raymond E. Goldstein from Cambridge's Department of Applied Mathematics and Theoretical Â鶹ÒùÔºics, who co-led the research. "It also shows the exciting results we can achieve when biologists, physicists and mathematicians work together on understanding the mysteries of life."

"By tracking a single structural protein, we gained insight into the principles behind the self-organization of the extracellular matrix," said Professor Armin Hallmann from the University of Bielefeld, who co-led the research. "Its geometry gives us a meaningful readout of how the organism develops as it grows."