On the Importance of Cell Division

In Harry Potter, wizards and witches have the magical ability to transfigure into different organisms. Not unlike Professor McGonagall’s remarkable ability to turn herself into a cat, stem cells also have a somewhat magical ability to differentiate into different kinds of cells, depending on the needs of the organism. For example, a baby starts out as a collection of stem cells, before differentiating into all the tissues and organs that comprise that baby. And while progenitor cells don’t get much press time, they promote the growth of various different kinds of cells. Together, these two cell types influence the way cells develop, and are especially fascinating to anyone studying abnormal growths in the body.

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Figure 1: The two types of stem cell divisions and their resulting daughter cells [Photo Link]
Hopefully you know that you have cells that divide and multiply. But even though this cell division is an everyday process that allows a baby to grow into an adult, or even for a person to recover from a cut, the scientific community doesn’t actually understand how it occurs in adults, or even really how to control cell division all that well in a petri dish. This could be problematic, given that abnormal growths are something that we don’t handle particularly well in old age. What do we do when our cells mutate, changing us from within at a molecular level and how do we prevent cells from mutating into those hard-to-kill cancer cells?

What we do know about cell division is that there are generally two ways of this happening. In Harry Potter, wizards can arise from wizarding families or from muggle born families, but both are normal occurrences. Similarly, cell division can occur asymmetrically or symmetrically, and both are normal occurrences. To further the metaphor, asymmetric cell division is when we divide a cell and get two different resulting cells (think a Muggle family ending up with one wizard/witch and one regular non-magic human). And just as in the wizarding world where we associate different stereotypes with wizards and witches of different backgrounds, scientists associate the two methods of cell division with different results (i.e. inhibiting or encouraging tumor formation).

In the brain, stem cells undergo asymmetric cell division by establishing a polarity within the cell, a spatial difference in the cell that helps them perform a specific function. Any slight imbalance in the cell polarity proteins that regulate this asymmetric cell division process can result in reduced differentiation of cells (which is seen in aging), and poorer repair during the myelination of neurons (demyelinating diseases). One wonders how a system in such fragile balance could possibly be responsible for years of healthy living, since failure to properly control cell division can result in abnormal growth and impaired differentiation.

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Figure 2: Glial progenitor cells and their resulting progeny [Photo Link]
There are a particular kind of cancerous brain tumor cells- precursor glioma cells- that act a lot like progenitor cells. Progenitor cells are like encouraging tiger moms, encouraging their daughter cells to pursue specific lifestyles. We know that precursor cancer cells have shown decreased asymmetric cell division and increased symmetric cell division. This suggests that asymmetric cell division somehow inhibits brain tumor formation, which sounds like we should tote asymmetric cell division as our champion against cancer. But just as we empirically stereotype families that identify as “pure-blood” in Harry Potter because we identify with Weasley’s family and not Malfoy’s, it’s worth noting that our opinion of asymmetric cell division as an inhibitor and a champion against cancer could change.

For example, consider the discovery that stem cells retain their ability to perform asymmetric cell division. After studying asymmetric cell division (ACD) in Drosophila flies, we know that deregulation of ACD is correlated closely with genetic instability and cancer-esque proliferation.

The ability for cancer cells to divide asymmetrically may provide them with a survival advantage during therapy, which suggests that asymmetric cell division is not in fact always tumor suppressive, but can also prolong a cancer stem cell population.

Cell differentiation is an incredibly nuanced process. Whether wizard or muggle, cells that divide asymmetrically or symmetrically have overcome an incredible evolutionary barrier and enable humans to heal, grow, and develop. The implication of stem cell research is boundless in terms of potential for medical treatment, and my next article about neural stem cells (NSCs) will fill you in on how crucial stem cells can be even before your body realizes it needs them!

References:

  1. Daynac M, Petritsch CK. Regulation of Asymmetric Cell Division in Mammalian
    Neural Stem and Cancer Precursor Cells. Results Probl Cell Differ.
    2017;61:375-399. doi: 10.1007/978-3-319-53150-2_17. Review. PubMed PMID:
    28409314.
  2. https://figshare.com/articles/_symmetric_and_asymmetric_stem_cell_divisions_/834733
  3. https://www.intechopen.com/books/evolution-of-the-molecular-biology-of-brain-tumors-and-the-therapeutic-implications/mechanisms-of-aggressiveness-in-glioblastoma-prognostic-and-potential-therapeutic-insights

 

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