Mechanical tensions in fly embryos: A key to evolution?

Mechanical tensions in fly embryos: A key to evolution?

Research teams from the University of Hohenheim and the RIKEN Center in Japan have conducted a comprehensive study of mechanical stress in fly embryos. These tensions arise during embryonic development when cells and tissues collide. They can have serious effects on animal development. In this study, two different strategies for controlling these tensions produced in different fly species were observed.

A central focus of the research is gastrulation, a crucial stage of development in which complex tissues are formed from simple cell layers. Mechanical stress can cause fatal deformations and malformations that endanger morphogenesis. In fruit flies (Drosophila melanogaster) in particular, it was found that a temporary head furrow functions as a mechanical collecting basin. If the formation of this structure is incorrect, serious malformations in the head and nervous system occur.

Different strategies for dealing with tension

In contrast, other species of flies, such as Chironomus riparius, have developed a different strategy: their cells divide obliquely or vertically, thereby reducing pressure on the tissue structure. Experimental changes in the orientation of cell divisions can ensure normal embryonic development. These results were independently confirmed by a working group at the Max Planck Institute in Dresden and show that evolution has produced various solutions to the problem of mechanical stress.

The importance of mechanical stresses could be far-reaching. They may play a key role in the emergence of new body plans during evolution. The research results were published in the renowned journal Nature and provide deep insights into the biophysical mechanisms at work in embryonic development.

Gastrulation and morphogenesis

Gastrulation, a morphogenetic process, brings about the spatial organization of blastomeres into the three germ layers (ectoderm, mesoderm, endoderm). This process is characterized by the internal restructuring of certain cells from the outer layer, which is achieved through changes in cell shape, especially apical contraction. In Drosophila, invagination of mesoderm and endoderm occurs as collective tissue units, not as individual cells.

A key to understanding these processes is the role of specific signaling components such as the morphogen Spätzle, which establishes a gradient in transcriptional activity. This leads to the expression of folded gastrulation and T48. These factors are crucial for the apical shape changes required for gastrulation. Actins and myosin 2 are the primary proteins that control the contractile properties of cells, thereby promoting tissue sculpting function.

Another interesting discovery is that mechanical feedback influences cell shape and behavior during gastrulation. This occurs by tension controlling the organization and contractile force of myosin 2. Such dynamics are crucial for maintaining tissue integrity and promoting coordinated morphogenetic movements.