Morfogen

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Morphogen - a substance that affects the future fate of a cell and has a different effect on it depending on its concentration. The so-called. A morphogenic model that assumes positional information is generated along a given axis by morphogen synthesis by its source, which may be, for example, another cell that is located at one of the axes. The diffusion of morphogen from this site leads to the formation of a morphogen gradient - depending on the distance from the source its concentration is different, which also has a different effect on the target cells, which differentiate in different ways. To release a specific expression pattern, the concentration of morphogen must exceed a certain threshold concentration.

A good example of this type of interaction in the development of the organism is the larval development of Drosophila melanogaster. In the Drosophila embryo, which is a large syncytium, Hunchback protein is located at an early stage of development with a gradient along the anterior posterior axis of the embryo. This protein is a transcription factor, which, depending on its concentration, activates the specific genes of the gaps. In general, transcription factors often function as morphogens in the early development of this insect, mainly because they are free to diffuse throughout the organism at this developmental stage (no cell membranes separate from each embryo nucleus).

Another example of the morphogenic activity can be the development of vertebrate limbs, where the role of morphogen is the sonic signaling hedgehog. As a result of its action, the expression of the HoxD genes is concentric in relation to the rear differentiation zone, which is necessary for the proper formation of the fingers.

Cell differentiation can also occur in slightly different ways: namely, it can also be associated with an "antitorfogene" gradient, ie the morphogen itself has the same concentration in a specific area, but its activity can be modified by a gradient of the inhibitor concentration of this morphogen. Examples of this type of interaction are the developmental activities of vertebrates that secrete inhibitors for BMP (bone morphogenetic proteins) and Wnt proteins.

Morfogeny Drosophila melanogaster

There are 4 groups of Drosophila melanogaster pupa's genes responsible for the proper development of her morphological body: Bibliography

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