Biologists at the Kansas State University found that a single gene called retinoblastoma (RB) is responsible for the evolution of single-celled organisms into multicellular ones, debunking previous theories that it took multiple genes to create multicellular life.
The same gene is also known to be defective in cancer patients and plays a critical role in the evolution into multicellular life. “Not only did we find a critical gene for multicellularity, it turns out to be a tumor suppressor and it is much easier to evolve multicellularity than anticipated.”
“RB plays a fundamental role in cell multiplication by regulating cell cycles just before DNA replication starts,” Olson adds. “Cancer occurs when this gene is defective. In terms of cell cycle and cancer progression, think of RB like the brakes on your car. When the brakes are defective, there is no way to control how the vehicle stops.”
Eric Hanschen, a doctoral student at the University of Arizona and co-researcher, adds that multicellularity has evolved several times independently. “It is well-known that plants, animals and fungi evolved independently, but so did red, green and brown algae, volvocine algae, slime molds and bacteria; it’s a process that has happened many, many times,” he says. “The result we find with RB is intriguing because this pathway and this gene are shared among so many of these independent multicellular groups, which are separated by hundreds of millions of years.”
The researchers compared the multi-cellular Gonium pectoral alga and its single-celled relative Chlamydomonas reinhardtii and found that the RB gene is present in both algae despite small structural cycle differences. And when they introduced the RB gene from Gonium into Chlamydomonas, the latter became multicellular.
“Gonium is representative of the first steps toward the evolution of complex multicellular organisms such as plants and animals,” Olson said. “These findings have the potential to help scientists understand the origin of cancer and may contribute to future abilities to treat and detect cancer.”