The immune system of these tasty little crustaceans can produce cells that are able to turn into various types of other cells -- including neurons -- in adults, according to work published in Developmental Cell this week. The discovery of these stem cell properties could maybe one day help us regenerate damaged brain cells.
How neurons are produced, and subsequently integrated into the brain, throughout our lives is called neurogenesis. Dysfunctions in this production process could lead to neurological diseases. In many adult organisms (from people to crustaceans), neurons in some parts of the brain are continuously resupplied, especially those that are exposed to constant damage -- such as eyestalks and smell circuits.
To trace the origins of nerve cells, a team led by Irene Söderhäll from Uppsala University and Barbara Beltz from Wellesley College turned to crayfish (or crawfish or crawdad depending on where you’re from). “The crustacean brain offers a perfect model because the generations of precursor cells are spatially separated from each other,” according to Beltz in a news release. First-generation neuronal precursors -- the stem cells that produce adult-born neurons -- reside in a brain region called the neurogenic niche. In crayfish, these can’t renew themselves: These precursors must be constantly replenished.
The researchers found that crayfish neuronal precursors were coming from their immune system. "The immune system is intimately tied to mechanisms of adult neurogenesis," Söderhäll says, "suggesting a much closer relationship between the immune system and nervous system than has been previously appreciated."
Until now, the source of neuronal precursors was unknown. Previous work has shown that the crayfish immune system relies on cells called hemocytes to deliver oxygen around the body (like our red blood cells). So, the team extracted and labeled hemocytes from donor crayfish and transferred them into recipient crayfish. Then they watched as the labeled cells populated the niche containing the neuronal precursors.
Within seven weeks of the transfusion, the hemocytes were producing neurotransmitters, New Scientist explains, the chemicals that neurons use to communicate with each other. Furthermore, the Scientist reports, the team could increase or decrease the number of cells within the neurogenic niche by altering the total hemocyte count.
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