differentiation

The differentiation in biology marks the transition from a poorly differentiated to a highly differentiated state. This process is of particular importance during the development of the fertilized egg cell into a complete organism. Disturbances in the differentiation process can lead to serious diseases such as cancer or malformations.

What is the differentiation?

Biological differentiation is about the specialization of undifferentiated stem cells into differentiated body cells. These processes play a particularly important role during embryogenesis and subsequent growth. Differentiation processes are also important for the maintenance of body functions in adult organisms.

Initially, undifferentiated stem cells still have the ability to transform into all other body cells. In the process, specialized body cells arise through several differentiation processes, which form the various organs and ultimately lose the ability to divide.

There are several types of stem cells. The so-called totipotent stem cells are still able to transform themselves into a complete organism. The pluripotent stem cells can in turn differentiate into all body cells. However, it is no longer possible for them to develop into individual organisms. Multipotent stem cells have already developed a certain differentiation into a certain cell line. However, they can still differentiate into all other cells of this cell line.

Function & task

Biological differentiation is one of the most important processes in the development of plant, animal or human organisms. During this process, among other things, develop body cells that are increasingly differentiated from a fertilized egg cell in several steps.

The fertilized egg cell is the first totipotent stem cell that is initially subject to cell division into four equal cells. Each of these four cells can develop into a completely genetically identical organism. When the four-cell stage is reached, the blastocyst, which consists of pluripotent embryonic stem cells, forms. These pluripotent stem cells can develop into the three germ layers ectoderm, endoderm and mesoderm via the next stage of differentiation and thus represent the starting point for all other body cells.

In contrast to the totipotent stem cells, however, these have already lost the ability to develop into genetically identical independent organisms.

Further cell lines emerge from the three cotyledons, which initially consist of multipotent stem cells. The multipotent stem cells are able to develop into all cell types of the respective cell line. These cells no longer have the ability to transform themselves into all other body cells, as they have already reached a higher degree of differentiation than the pluripotent stem cells.

In animal and human organisms, the process of differentiation is associated with a determination. Determination describes the establishment of a specialization once taken, whereby the further development of the cell lines is passed on by epigenetic means. Of course, cells that have already been pre-differentiated will differentiate further into the cells of the corresponding cell line as part of their determination.

Although the entire genetic information of each individual cell is identical, it is called up differently depending on the cell type through gene expression. This means, among other things, that in a liver cell, for example, only the genetic information for liver function is decoded, while all other information remains unread.

Differentiation is influenced by various external or internal factors. Hormones and growth factors play an important role. The cell contacts to neighboring cells also determine the direction of differentiation.

A transdetermination can occur under certain conditions. The cell determination is changed. This is particularly important in wound healing. If the cells are then already differentiated, they lose their differentiation in these cases and differentiate again. If this process is disturbed, however, cancer can occur.

Differentiation is essential for the organism to function at all as a uniform biological system.

Illnesses & ailments

In the context of cell differentiation, however, disturbances can occur, which may lead to organ malformations during embryogenesis. There are some genetic diseases with a variety of organ dysplasias. In addition to malformations of the internal organs, the external appearance is often disharmonious.

However, there are also non-genetic causes of organ malformations. One example is renal agenesis in the absence of amniotic fluid. Since the human embryo can only develop within the amniotic fluid, the lack of space here leads to faulty organ differentiation, whereby other organs and tissues are also affected.

Drugs can also disrupt the differentiation process during embryogenesis. A well-known example is the sedative Contergan, which led to damage to the growth development of the fetus during early pregnancy. This became public in 1961 with the so-called Contergansandal.

However, it can also happen that cells that are already differentiated dedifferentiate and then multiply in an uncontrolled manner. This is the situation with cancer. The more the cells have de-differentiated, the more malignant the tumor. As already mentioned, dedifferentiation is necessary in some cases when there is a greater need for cell growth. This is the case with wound healing, among other things. In these processes, however, the dedifferentiation is followed by a differentiation of the cells. If differentiation then fails, however, cancer develops.

Somatic mutations in the cells can also affect genes that influence differentiation. Therefore, the likelihood of developing cancer increases over the course of life.