Flatworm Regenerates Without Centrosomes
Posted on January 6, 2012
Schmidtea mediterranea is a freshwater flatworm found in southern Europe and Northern Africa. If the worm is cut into tiny pieces, each piece will grow into a perfectly normal flatworm within days. Researchers discovered that this flatowrm regenerates without centrosomes, a structure long thought necessary for cell division. They are the first creature known to not have centrosomes in their cells.
Centrosomes were thought to play a central role in cell division by laying down track-like spindles onto which the cells sort their dividing DNA. Centrosomes were seen as so important to cell division that all animals were assumed to have them.
Researchers from the University of California, San Francisco (UCSF) and the Stowers Institute for Medical Research published the report in the journal Science. Wallace Marshall, PhD, an associate professor in the Department of Biochemistry & Biophysics at UCSF, who led the research, says the fact that flatworms lack centrosomes calls into question their purpose. Marshall says, "Clearly we have to rethink what centrosomes are actually doing."
The original intention of the study was to see what happened to the worm when it lost its centrosome. The researchers manipulated the flatworm to knock out genes needed to assemble these centrosomes. Without centrosomes the researchers thought the worms would lose their ability to regenerate normally. They were amazed to find that losing these structures didn't affect the worms' ability to regenerate at all. Then they looked more carefully at the worms and discovered that the flatworms never had centrosomes in the first place.