2. Developmental Potential and Differentiation

Now that we have established some fundamental principles underlying neural development (and development in general), let's revisit this image:

As a reminder, all of these cells have identical genomes, and their differences in appearance and function is regulated by gene expression. It's important to note that these differentiations specify along the way. What a cell can become is called cell potential, and what a cell does become is called cell fate (i.e., the cell's final, developed state).

At the very beginning of development (prior to the formation of the blastula), cells are considered to be totipotent, or to have complete developmental potential. Totipotent cells can potentially become any cell, including all pictured cells and more (e.g., placental cells), as differentiation has not started. Another way to think about complete cell potential is to think of the cell fate as absolutely undetermined. Totipotent cells are commonly referred to as stem cells, which may sound familiar if you've encountered news about advancements in stem cell therapy in recent years.

To perhaps state the obvious--but I'm going to do it anyway--cell potential reduces as cell development progresses. Cells soon become pluripotent, meaning that they can become any cell in the body, including all cells pictured above. Pluripotent cells have a slightly more determined cell fate than totipotent cells, but are still considered stem cells.

The next categorization of cell potential is multipotency. Multipotent cells are generally compartmentalized, but still have room to develop into any cell within that compartmentalization. We can still refer to multipotent cells as stem cells, but they now require a category in the front. A good example of this is a neural stem cell, which must become a cell in the brain, but it can become any cell in the brain (e.g., neuron, astrocyte, etc.). Do NOT worry about the different types of brain cells for now. Don't do it. That's a different lecture. Compartmentalize like your cells do.

A cell that has reached its cell fate, or final development potential, is called a unipotent cell (uni = one; one potential). At this point, this cell has found its rightful place in your body.

Here is a chart that may help you visualize this loss in cell potential (or gain in cell fate) over the course of development:

A mnemonic device that I find useful for remembering this:

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Play

Minecraft

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Lastly, as a small exercise, try to categorize the potency of each stage of cells below. The stem cell has been noted as pluripotent for you.

As always, I hope you learned something new (even if it is a trivial factoid) and are finding developmental neurobiology interesting (even if just a little bit more). Hope to see you back.

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