Differentiation is the process wherein unspecialized stem cells give rise to specialized cells with a deliberate switch from proliferation to specialization. Here unspecialized stem cells are those that have not been assigned a specific phenotype or role to play in the functioning of the living organism.
The stem cell, while differentiating, typically goes through several stages, becoming more and more specialized at each step. Each step bringing it closer to its function in the body accompanied by various alterations such as changes to cell morphology, metabolic activity, membrane potential, and responsiveness to certain signals. These signals may be composed of mostly growth factors, cytokines as well as epigenetic processes namely DNA methylation and chromatin remodeling. When embryonic stem cells undergo such differentiation they divide to give one duplicate stem cell (self-renewal) and one differentiated daughter cell becoming more and more mature as it moves downstream.
The process of differentiation of the stem cell is tightly regulated by and prompted by internal and/or external signals.
- The internal signals that trigger the differentiation are controlled by the stem cell's genes, which are information presented in the form of long strands of DNA. They carry coded instructions for all cellular structures and functions.
- The external signals for differentiation can include chemicals secreted by surrounding or far away cells, physical contact with neighboring cells, and specific molecules in the microenvironment.
The stem cell's DNA can acquire epigenetic marks that restrict DNA expression of the cell through the interactions of these signals during differentiation. This information can be further passed down to daughter cells.
The mechanisms involved in differentiation, especially those of embryonic stem cells is being widely studied by scientists especially with regards to debilitating diseases such as Parkinson's disease and cancer.