What makes a cell a stem cell, biochemically speaking?
Thanks for your help,
Rob
It’s an analogy from stem and leaves.
The stem cell is the cell with no particular character of its own; it can do anything, but it hasn’t done anything.
Except divide.
It stays a stem cell when it divides. The second cell can also stay a stem cell.
Or it can respond to various chemicals made by other cells to start changing into a specific kind of cell that the other cells need. This is analogous, in the metaphor, to going down one branch off a stem.
For instance, in the bone marrow, a stem cell can divide and give rise to a stem cell and an erythroblast.
The erythroblast will divide a few times, giving rise to other erythroblasts.
Some (or all) of them will mature, and their great-great-grandcells will be red blood cells.
It’s believed that the stem cells in the bone marrow can grow into any kind of blood cell (white, red, or platelet; lympho, neutro, or eosino).
Stem cells in an early embryo or fetus, on the other hand, can grown into ANY KIND OF CELL WHATSOEVER. For this they get a small robe and crown, and the honorary designation “totipotential”.
I wish someone would have called me “totipotential” when I was getting out of high school.
My favorite tumor (not 800 lbs though) is the teratoma, which must be a totipotential stem cell gone wrong. I have described it as a “baby in a blender”. It tries to make all kinds of tissues, but with almost no organization. Hair, teeth, placenta, skin, thyroid, esophagus, neural tissue… uh oh, immature neural elements are bad news…
This is my best answer based on my knowledge as a pathologist. I am sure there are more active docs on the boards who could improve on it greatly.
Gabriela
I see I missed the point of the OP. You wanted to know biochemically.
I doubt anyone knows biochemically; you’d have to unravel the entire genetic code to… oh, wait, that’s been done.
You’d have to know what protein each gene in the stem cell specifies, particularly the self-regulatory proteins that turn other genes on and off, so you could uncover the mystery of why it has the potential to become any kind of cell.
I’d love to see that research and have it explained to me, only I’m afraid I’d have to wait until 2300 AD.
Anybody have a better grip on how far we’ve come to understanding the molecular biochemistry of the totipotential stem cell?