Tokyo, Dec 26 (IANS): A team of Japanese scientists has revealed for the first time that a protein better known for its role in the immune system tells developing cells to stick together.

Tohoku University scientists have provided experimental evidence that cell stickiness helps them stay sorted within correct compartments during development.

Scientists have long observed that not-yet-specialised cells move in a way that ensures that cell groups destined for a specific tissue stay together.

Way back in 1964, American biologist Malcolm Steinberg proposed that cells with similar adhesiveness move to come in contact with each other to minimise energy use, producing a thermodynamically stable structure.

This is known as the differential adhesion hypothesis.

New research, detailed in the journal Nature Communications, said that how tightly cells clump together, known as cell adhesion, appears to be enabled by a protein kneed as "Toll-1".

Erina Kuranaga of Tohoku University's Laboratory for Histogenetic Dynamics said: "Our study showed, for the first time, that cell sorting is regulated by changes in adhesion."

Kuranaga and her team conducted experiments in fruit fly pupae, finding that a gene, called Toll-1, played a major role in this adhesion process.

Using fluorescent tags, Kuranaga and her team observed the Toll-1 protein is expressed mainly in the posterior compartment. Its fluorescence also showed a sharp boundary between the two compartments.

Further investigations showed Toll-1 performs the function of an adhesion molecule, encouraging similar cells to stick together.

This process keeps the boundary between the two compartments straight, correcting distortions that arise as the cells divide to increase the number.

Interestingly, Toll proteins are best known for recognising invading pathogens, and little is known about their work beyond the immune system.

"Our work improves understanding of the non-immune roles of Toll proteins," said Kuranaga.

She and her team now plan to study the function of other Toll genes in fruit fly epithelial cells.