Cell Differentiation
During embryonic development, cells differentiate into various cell types that have specific structures and functions. These differentiation processes are regulated by the induction and repression of certain genes at certain times, and errors that occur during such processes often leads to developmental disease. Related to cell differentiation is the concept of cell fate, which is controlled by many factors, including cell-cell interaction (eg: Hedgehog and Notch signaling pathways), the release of morphogens and hormones, and the environment in which the cell is located. Unlike differentiated cells, stem cells are not terminally differentiated and can divide indefinitely. As such, stem cells offer potential in the treatment of various diseases and cancers.
Morphogenesis
The differentiation of cells and tissues in embryonic development that creates the form and structure of different parts of the body. In plants morphogenesis is usually caused by differential growth and can continue throughout the lifetime of a plant. Animal morphogenesis happens through growth and cell movement and an organism’s form is determined early in development. Homeotic (Hox) genes play a key role in controlling the body plan of embryos and in determining what structures are formed in certain areas of the body. Mutations in these genes can cause the wrong structures to form, the structure to not form properly, or the structures to not form at all.
Tissue Patterning / Pattern Formation
One of the mechanisms by which stem cells can divide is through symmetric division, where sisters cells only become different as a result of external factors. This creates a pattern of differentiated cells, which later contribute to tissue patterning in an organism. One such way this can happen is when a morphogen, an inductive secretory molecule that induces differentiation, is secreted and a gradient pattern of differentiation is created, centered around the morphogen source. The development of specific body structures from an embryo is due to the secretion of morphogens from a secreting organizer tissue. Additionally, morphogens help create patterns in the body, also known as segmental patterns. For instance, the repeating pattern on the drosophila abdomen is due to a pattern of organizer tissue secreting morphogens to surrounding cells, which become organizer tissue themselves and continue to secrete morphogens to the surrounding cells, resulting in a segmental pattern.