Science Buddies: "Ask an Expert"

Hello, I'm doing research on stem cells for a project at school, and I'm a bit curious on the question above: What triggers the first differentiation of embryonic stem cells in the early stages of the zygote? Also, how do these early cells regulate differentiation, that is, what is the starting process causes the gene switch to turn on or off for specialization?

HI
Here is an excerpt from Stem Cell Basics 2

"Scientists are just beginning to understand the signals inside and outside cells that trigger each step of the differentiation process. The internal signals are controlled by a cell's genes, which are interspersed across long strands of DNA and carry coded instructions for all cellular structures and functions. The external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment. The interaction of signals during differentiation causes the cell's DNA to acquire epigenetic marks that restrict DNA expression in the cell and can be passed on through cell division."

Here is the full article link so you can use it for further research if you choose to
https://stemcells.nih.gov/info/basics/2.htm

Hope this helped
Dominique