Timelapse Video Reveals Electric Face in Embryonic Tadpole

Posted on July 18, 2011

Biologists at Tufts University report that bioelectrical signals are necessary for normal head and facial formation in an organism. They have also captured the process in an amazing timelapse video that reveals never-before-seen patterns of visible bioelectrical signals outlining where eyes, nose, mouth, and other features will appear in an embryonic tadpole. The researchers are calling this an "electric face."

The Tufts biologists found that, before the face of a tadpole develops, bioelectrical signals cause groups of cells to form patterns marked by different membrane voltage and pH levels. When stained with a dye, hyperpolarized (negatively charged) areas shine brightly, while other areas appear darker, creating an "electric face."

Dany S. Adams, Ph.D. Adams, a research associate professor in the Department of Biology in the Tufts School of Arts and Sciences, says, "When a frog embryo is just developing, before it gets a face, a pattern for that face lights up on the surface of the embryo. We believe this is the first time such patterning has been reported for an entire structure, not just for a single organ. I would never have predicted anything like it. It's a jaw dropper."

The news release from Tufts says Adams first made the discovery in September 2009. She was making time-lapse movies of early stage tadpole development. The images were coming out particularly clear, so she decided to leave the camera on overnight, even though she anticipated that as the developing embryos began to move, the images would likely become too blurred to be useful. When Adams arrived the next morning, the image on the computer monitor was out of focus as she expected. However, when she finished processing the rest of the images, she found they were clear.

Adams says the images were "unlike anything I had ever seen. I was completely blown away. I think I thought something like, 'OK, I know what I'll be studying for the next 20 years.'"

The imagery revealed three stages, or courses, of bioelectric activity.

First, a wave of hyperpolarization (negative ions) flashed across the entire embryo, coinciding with the emergence of cilia that enable the embryos to move. Next, patterns appeared that matched the imminent shape changes and gene expression domains of the developing face. Bright hyperpolarization marked the folding in of the surface, while both hyperpolarized and depolarized regions overlapped domains of head patterning genes. In the third course, localized regions of hyperpolarization formed, expanded and disappeared, but without disturbing the patterns created during the second stage. At the same time, the spherical embryo began to elongate.
The researchers also found that disrupting the bioelectric signaling correlated with craniofacial abnormalities.

The Tufts researchers note that more research is needed to discover if bioelectrical signaling works the same in frogs as in other animals, including people. There is the possibility an "electric face" exists in human development.

Tufts Post Doctoral Associate Laura N. Vandenberg, Ph.D., was first author of the paper entitled "V-ATPase-dependent ectodermal voltage and pH regionalization are required for craniofacial morphogenesis." Ryan D. Morrie, a biology major in the School of Arts and Sciences, was second author. The research will be published in the journal Developmental Dynamics.

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