Scientists at Academia Sinica have identified a new form of cell division that occurs without the replication of DNA, challenging the scientific consensus on one of the most basic biological processes.
Since the 19th century, scientists have known of only two main types of cell division in animals — meiosis in germ cells (sperm or egg cells) and mitosis in somatic cells, which comprise all other cells in the body.
However, in a new paper published in the British scientific journal Nature, an Academia Sinica team described a previously unknown form of cell division which, unlike mitosis, does not involve the duplication of DNA.
Photo courtesy of Academia Sinica
The team, led by Chen Chen-hui (陳振輝), an assistant research fellow at the academy’s Institute of Cellular and Organismic Biology, held a news conference on Monday to explain their findings.
To conduct the research, Chen’s team used a custom-made computer tagging system to color and track individual cells on zebrafish larvae as they developed.
To do so, the researchers had to catch and anesthetize the 0.5cm fish every 12 hours and photograph them under a high-powered microscope.
They discovered that during a specific stage in the fishes’ growth, some of the outer layers of their skin cells underwent up to two rounds of cell division (one cell becoming four cells) by splitting, rather than duplicating, their DNA.
The phenomenon, called asynthetic fission, is a temporary measure used to expand the coverage of epithelial cells, or outer skin cells, during a period of rapid growth, Chen said.
According to a video produced by Nature, the process happens so quickly that cells even appeared to make “mistakes,” such as not cleanly separating the DNA between the new cells.
However, within a few weeks the zebrafish get rid of the unusual cells and replace them with regular cells containing normal amounts of DNA, the video said.
While the team is still in the early stages of understanding the process, this mode of cell proliferation might occur in contexts beyond zebrafish skin expansion, Chen said.
The article, titled Skin cells undergo asynthetic fission to expand body surfaces in zebrafish, was published on Wednesday last week.
The journal’s video on the research, A new kind of cell division, was released on Sunday.
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