Fruit fly bodies bank stem cells

Protective pockets hold reserves until it's time for stem cells to become intestinal cells

Stem cells lead sheltered lives. A new study of fruit flies shows how stem cell precursors create their own niches where the developing cells can safely hang out. These cell banks give the fly a reserve of stem cells to draw on later to create and replenish organs, make new cells or repair wounds.

A stem cell in the fruit fly gut divides, creating a daughter cell that wraps itself around its mother and siblings and prevents them from turning into specialized tissues, researchers from Columbia University report online January 7 in Science.

The stem cell, called an adult midgut progenitor, is a precursor to intestinal cells. The team found that the stem cell sends a signal, in the form of the protein Notch, to one of its daughters. The daughter cell then becomes a peripheral cell, which acts “like an octopus covering other cells with its tentacles,” says Benjamin Ohlstein, a geneticist and developmental biologist at Columbia University Medical Center in New York City who led the research. In Drosophila larvae, these peripheral cell holding pens block differentiation signals from reaching the stem cell herd during gut development.

During the flies’ larval stage, the peripheral cells protect their stem cell siblings from becoming digestive cells prematurely, the team reports. When the fly larva undergoes metamorphosis into an adult, the niche breaks down and most of the cells that had been sequestered inside begin to form the gut. A few retain their identities as stem cells in the intestines and stand at the ready to replace cells that are damaged or have sloughed off.

These findings could help scientists understand how stem cells maintain their identities while an organism develops, and may have implications for cancer and regenerative medicine. Ohlstein speculates that cancer stem cells may also create their own niches, allowing them to move around the body. “It’s like driving across the country,” Ohlstein says, “and instead of staying in a hotel, you take your own tent with you.”

Scientists might also use niche-forming cells to keep stem cell populations in an undifferentiated state in the laboratory.

POCKET FULL OF STEM CELLS Peripheral cells (shown in red) form pockets that shelter undifferentiated stem cells (green) that will later form the adult fruit fly gut. Image courtesy of Science/AAAS

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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