Cell differention and gravity

[cloudyday2]

We start from a single cell that differentiates into blood cells, bone cells, etc. Somehow this differentiation creates bones, muscles, organs of the proper shape in the proper location.

If an animal like a mouse developed from single cell to adult in zero gravity would it look significantly different? I've tried to google this in the past, but there isn't much. Maybe somebody else knows about this?

My theory is that the differentiation partly responds to need of the organism and gravity is a factor. Without gravity the bones might develop very differently or not at all.

 

[FrumiousBandersnatch]

If an animal like a mouse developed from single cell to adult in zero gravity would it look significantly different?

My theory is that the differentiation partly responds to need of the organism and gravity is a factor. Without gravity the bones might develop very differently or not at all.

Anatomically, it wouldn't be significantly different (mammal embryos develop normally in space) - I don't know anything to suggest embryonic differentiation depends on gravity - implantation can occur in any orientation; but postnatal development in microgravity would result in hypertrophy of supporting skeletal muscles, and significantly weakened bones and heart. Gravity-dependent developmental milestones involving posture and movement would probably be severely affected.

 

[cloudyday2]

Anatomically, it wouldn't be significantly different (mammal embryos develop normally in space) - I don't know anything to suggest embryonic differentiation depends on gravity - implantation can occur in any orientation; but postnatal development in microgravity would result in hypertrophy of supporting skeletal muscles, and significantly weakened bones and heart. Gravity-dependent developmental milestones involving posture and movement would probably be severely affected.

What I have wondered is if differentiation is driven by forces. Like maybe a very young fetus flexes muscles and that flexing causes some stem cells to become bone cells and other stem cells to become muscle cells and so on. The fact that bones have a shape that "works" from an engineering standpoint might be due to the "need" to develop that shape in response to forces of muscles and gravity - as opposed to some blueprint within the DNA that specifies that shape.

 

[FrumiousBandersnatch]

What I have wondered is if differentiation is driven by forces. Like maybe a very young fetus flexes muscles and that flexing causes some stem cells to become bone cells and other stem cells to become muscle cells and so on. The fact that bones have a shape that works from an engineering standpoint might be due to the "need" to develop that shape in response to forces of muscles and gravity - as opposed to some blueprint within the DNA that specifies that shape.

There are various signals that cause cells to differentiate, not all well-understood, but including biochemical signal concentration gradients, cell-to-cell chemical signalling, and 'simple' mechanical influences (e.g. cellular matrix elasticity). Epigenetics has an important role. There's not really a DNA blueprint; if anything, it's more like a recipe, but such analogies are probably more misleading than helpful. The wiki article gives a reasonable overview.

 

[DogmaHunter]

We start from a single cell that differentiates into blood cells, bone cells, etc. Somehow this differentiation creates bones, muscles, organs of the proper shape in the proper location.

If an animal like a mouse developed from single cell to adult in zero gravity would it look significantly different? I've tried to google this in the past, but there isn't much. Maybe somebody else knows about this?

My theory is that the differentiation partly responds to need of the organism and gravity is a factor. Without gravity the bones might develop very differently or not at all.

It's been a while, but I remember a documentary about pregnancy and birth in zero gravity and experiments they did with rats and jellyfish and stuff.

Anatomically, the animals were just fine in the sense that all "parts" found themselves where they would be expected.

There were issues of bone densities and stuff, but (again: if I remember correctly) those issues could be overcome when returning to non-zero-gravity and then "training" the body to get used to the forces again.

Again if memory serves me right, the biggest issues was that the "zero gravity creatures", had no sense of "up" and "down".

I clearly remember them dropping certain of these "zero gravity" animals face-up in a fish tank and doing the same with control animals that were born on earth.

As they descended down the water to the bottom, the control creatures all turned around so they hit the bottom face-down. The zero-gravity creatures did not.

Although I guess they could overcome that side-effect as well, by "re-training" their sense of balance in the same way as their muscles, when back under the influence of gravity.

 

[cloudyday2]

I have read that the bones in the human ear are actually reptilian jaw bones. At some time there must have been a mistake that duplicated the jaw bone DNA.

I imagine a human fetus very early in development might have two identical jaws. The reptilian jaw is not "needed" as a jaw, so it doesn't develop much while the new jaw is "needed" and does develop. Let's say we surgically removed the new jaw from the human fetus at this early stage. Would the reptilian jaw develop more fully, because it is now "needed"?

My theory is that our bones and organs and arteries are engineered by "need". There may be genetic code specifying that a certain bone should exist, but the actual shape and size of that bone might be determined by the engineering needs. A muscle pulling on a nascent bone might make it grow in a way that "works" from an engineering standpoint. The actual genetic specification can be very simple.

It seems like a person could test this idea by using a computer simulation. I hope what I said makes sense.