AsianScientist (Apr. 8, 2013) – Researchers in Japan have developed a new technique that enabled them to visualize the distribution of retinoic acid in a live zebrafish embryo, in real-time.
The report, published in the journal Nature, describes how researchers at the RIKEN Brain Science Institute observed two concentration gradients going in opposing directions along the head-to-tail axis of the embryo, thus providing long-awaited evidence that retinoic acid is a morphogen.
Retinoic acid has been thought to be a morphogen, a signalling molecule that diffuses throughout the embryo switching genes on and off and imparting different cell fates depending on its concentration. However, retinoic acid concentration gradients had never before been visualized because retinoic acid cannot be tagged with the commonly used green fluorescent protein (GFP).
“Until now no one had succeeded in monitoring the concentration of retinoic acid in real-time in a live embryo, and there was no direct data proving the existence of a retinoic acid gradient in the vertebrate embryo,” explains Dr. Atsushi Miyawaki, who led the research.
In order to monitor the concentration of retinoic acid in live zebrafish embryos at the early stages of their development, Miyawaki and colleague Dr. Satoshi Shimozono labeled the receptor for retinoic acid with genetically-encoded, colored fluorophores. Based on the principle of fluorescence resonance energy transfer (FRET), the tags allowed them to visualize the presence of retinoic acid and quantitatively determine its concentration over time.
By combining this technique with pharmacological and genetic manipulations, Miyawaki and his team demonstrated the presence of two linear retinoic acid concentration gradients across the antero-posterior axis of the embryo, from the trunk area to the head and the tail. Their findings suggest that retinoic acid diffuses quickly, thus establishing stable and robust gradients that are resistant to external perturbations.
“A better understanding of the gradients of retinoic acid is essential for research into the patterns of tissue development. It is necessary if we ever want to control the development of three-dimensional tissue structures from induced pluripotent stem cells, for regenerative medicine for example,” said Miyawaki.
Source: RIKEN; Photo: wellcome images/Flickr/CC.
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