Scientists discover an unexpected influence on dividing stem cells' fate.
NEW YORK, N.Y., February 10, 2017 -- Stem cells differ from ordinary somatic cells because they are able to duplicate themselves or differentiate into skin cells, liver cells, or virtually any of the body's specialized cell types.
But how is the choice made by stem cells?
Scientists at The Rockefeller University have discovered that it depends on whether tiny organ-like structures known as organelles are allocated properly within the dividing stem cell.
The body's tissues develop properly and maintain themselves only if renewal and differentiation are carefully balanced.
"Our experiments suggest an unexpected role for the positioning and inheritance of cellular organelles, in this case enzyme-filled peroxisomes, in controlling this intricate balance," said senior author Elaine Fuchs.
The outer section of the skin, the epidermis, provides a protective barrier for the body, and stem cells reside deep within it.
During development, these cells divide so that one renewing stem cell daughter remains inward while the other daughter differentiates and moves outward to become part of the epidermis' outer layers.
The researchers wondered how skin cells first emerge and begin this transition.
Working with developing mouse skin, they devised an approach to identify genes that help guide the balance between new cells that either stay stem-like or differentiate.
The protein Pex11b is associated with the membrane that surrounds the peroxisome, an organelle that helps to free energy from food.
The protein seems to work by making sure the organelles are in the right locations so they can be divided between the daughter cells.
In cells that lacked Pex11b, peroxisomes weren't divvied up evenly: in some cases, one daughter cell ended up with all of the peroxisomes and the other didn't get any at all.
In cells whose peroxisome distribution was disrupted, cell division took longer. The mitotic spindle that separates the daughters' genetic material didn't align correctly.
Depleting skin stem cells of Pex11b led to fewer daughter cells able to differentiate into mature skincells.
The researchers moved peroxisomes around in the cell using a sophisticated laboratory technique, with the same result.
They concluded that if the peroxisomes are in the wrong positions during cell division, no matter how they get there, the process slows down.
The effect for the whole organism was dramatic: if peroxisome positioning was disrupted in the stem cells, the mouse embryos could no longer form normal skin.
Some evidence already suggested the distribution of organelles, including energy-producing mitochondria, can influence the outcome of cell division.
"We have shown for the first time that this phenomenon is essential to the proper behavior of stem cells and formation of the tissue," said Fuchs.
Citation: Amma Asare, John Levorse, Elaine Fuchs, "Coupling organelle inheritance with mitosis to balance growth and differentiation," Science, 2017; 355 (6324): eaah4701 DOI: 10.1126/science.aah4701
Contact: Elaine Fuchs, email@example.com
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|Title Annotation:||Basic Research|
|Publication:||Stem Cell Research News|
|Date:||Feb 13, 2017|
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