Bioelectric fields shape embryo development in frogs

Electrical gradients within developing embryos have been shown to control the directional migration of cell populations.

During embryo development, clusters of cells are arranged in space to shape the body plan so that tissues and organs grow in the right place. This process is controlled by many cues including chemical, mechanical, and electrical signals transmitted between cells. Until now, the role of bioelectrical fields was not well understood. A team of scientists at the Technical University of Dresden, Germany, have revealed how electrical fields within the developing embryos of frogs act like pathways to direct the migration of cells.

'We have characterised an endogenous bioelectric current pattern, which resembles an electric field during development, and demonstrated that this current can guide migration of a cell population known as the neural crest,' said Dr Elias Barriga, who led the study published in Nature Materials.

Measuring the electrical gradient across the embryo of Xenopus laevis, a species of frog, the team discovered that they define the path of movement of the neural crest, a process known as electrotaxis. The neural crest is part of the embryo which goes on to form the bones of the face and the neck, and parts of the nervous system. They found that this cell cluster follows the electric field from its positive to negative charge. By reversing the direction of the field, the researchers could direct the neural crest to migrate in the opposite direction.

The authors hypothesised that these electrical fields are generated within the embryo by the bending of a structure known as the neural fold. It has been proposed before that mechanical stresses caused by this bending may activate stretch-sensitive ion channels to generate a charge. By manipulating these processes, the team showed that the relationship between the bending and the ion-channels is important for generating an electrical field to guide the neural crest.

The question remained of how the neural crest cells were able to perceive and respond to the bioelectric field. To answer this, the team turned their attention to an enzyme called voltage-sensitive phosphatase. When the team knocked out this enzyme, the cells' migratory response to electrical fields was inhibited, suggesting their ability to sense electrical gradients was mediated by this enzyme.

'This paper bridges an important, decades-old gap in bioelectricity research, and it is deeply rewarding to be part of the ongoing renaissance in developmental bioelectricity,' said Dr Fernando Ferreira, postdoctoral scientist and first author of the study. 'In a broader perspective, we have now introduced another player into the intricate process of tissue morphogenesis. The question is now, how does this fit into already established frameworks of mechanical and chemical cues during embryogenesis?'

The work opens up new avenues for investigation into embryogenesis, and the team hope their findings could also provide insight into cell mechanisms behind wound healing and cancer development.