Cell differentiation

Cell differentiation is the process by which stem cells change from one type to a differentiated type. Usually, the cell becomes a more specialized type. Differentiation occurs many times during the development of multicellular organisms as it transforms from a simple ensemble to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and produce fully differentiated daughter cells during tissue repair and normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically alters cell size, shape, membrane potential, metabolic activity, and response to signals. These changes are largely due to highly controlled modifications of gene expression and are the subject of epigenetic studies. With few exceptions, cell differentiation almost never involves changes in the DNA sequence itself. Although metabolic composition does change dramatically, stem cells are characterized by an abundance of metabolites with highly unsaturated structures, the levels of which decrease with differentiation. Thus, despite having the same genome, different cells may have very different physical characteristics.