Bioscientists know a great deal about cell division, but there is one great mystery that remains unsolved: what actually causes a cell to divide. This is especially relevant to cancer studies, where biologists want to know more about the rampant cell division that leads to cancer. A research team from the University of California, San Diego set out to solve this puzzle and found a rather unexpected answer.
“How cells control their size and maintain stable size distributions is one of the most fundamental, unsolved problems in biology,” says Suckjoon Jun (image left, courtesy UCSD), professor of molecular biology at UCSD. “Even for the bacterium E. coli, arguably the most extensively studied organism to date, no one has been able to answer this question.”
Some theories assert that cells divide once they reach a certain size. Others propose that there is a time limit after which the cells are forced to divide. Jun found, surprisingly, that the answer was neither. “Specifically, we showed that cells sense neither space nor time, but add constant size irrespective of their birth size." That is, the cells are set to grow by some set amount, regardless of how large they are at birth.
(An E. coli cell, from birth to division. Courtesy UCSD)
What impresses Jun most about the discovery is that it applies to two bacteria that are different in most every way.
“E. coli and B. subtilis are one billion years divergent in evolution, and they are the textbook examples of the diversity of molecular details for biological controls in different bacterial species,” Jun said in a recent UCSD press release. “Thus, their sharing the same quantitative principle for size maintenance is a textbook level discovery.”
This discovery implies that years of evolution has not changed this fundamental condition of cell division, and thus it is likely that most cells behave this way. Jun plans to determine how ubiquitous this property is and then focus on its applications to cancer. Namely, there might exist an exact constant by which cancer cells might grow.
Jun’s research effort was supported by a $240,000 grant from the Pew Charitable Trusts, a $1.6 million award from the Paul G. Allen Family Foundation, and a $1.15 million grant from the National Science Foundation to help them present their research to high school and college students to help them better understand the field of quantitative biology.
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