The Sticky Truth Behind Cell Development

By observing fruit fly cells, scientists in Japan found a key protein for cell adhesion, allowing cells to stick together during development.

AsianScientist (Oct. 20, 2021) – Sticky situations help keep cells in distinct compartments during development, scientists from Japan reported in Nature Communications. The study detailed the role of a protein in clumping cells together, also called cell adhesion.

During embryonic growth, cells start out in an unspecialized state without specific functions like transmitting information for brain cells or carrying oxygen for red blood cells. As they gradually become specialized, these cells are sorted into larger groups of tissues and organs, teaming up with other cells bearing similar functions.

Researchers have long been studying how cells move and find each other—and importantly, stay together once found—during the complex process of development. According to the differential adhesion hypothesis, cells with similar adhesive or sticky properties likely come into contact with each other, forming a stable structure while minimizing energy use.

In theory, the concept made sense, but no one had demonstrated it yet in living animal tissues. To fill this gap, a team from Japan’s Tohoku University experimented on fruit fly pupae, showing how adhesion helps maintain the boundaries between cell populations.

During fruit fly development, cells cluster into separate regions on the abdominal surface, with each region further divided into the anterior and posterior compartments. By using light-emitting molecular tags, the team found a protein called Toll-1 in the posterior compartment. The tagged proteins showed up in a distinct line, marking the border between the compartments.

To check whether Toll-1 was responsible for adhesion, the researchers created clones with greater Toll-1 expression, observing even straighter boundaries than normal. Moreover, expressing Toll-1 in naturally non-adhesive cells led to similar clumping activity as other known adhesion molecules.

By encouraging similar cells to stick together, the boundary is kept intact. Thanks to Toll-1, these separate cell populations are effectively prevented from mixing even as more cells are added to the picture. The findings not only shed light on the mechanisms behind cell adhesion, but also revealed a new function for Toll proteins.

These proteins are known for their role in immune defenses, where they help recognize invading microbes, but it turns out they are crucial to development, too. Moving forward, the team aims to investigate the functions of other Toll proteins in fruit fly tissues.

“Toll-1 may have been adopted to play a role in development that is different from that of the Long-Toll proteins. This compelling possibility raises the stakes to better characterize the underrepresented non-immunity functions of Toll proteins,” the authors concluded.

The article can be found at: Iijima et al. (2020) Differential Cell Adhesion Implemented by Drosophila Toll Corrects Local Distortions of the Anterior-posterior Compartment Boundary.


Source: Tohoku University; Photo: Pixabay.
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