Zebrafish Mutant Yields Development Clues

Researchers using zebrafish as a model system have found that a single protein (the transmembrane protein called Strabismus/Van Gogh) facilitates the movements of cells within the developing embryo. This finding was reported in the August 2002 issue of Nature Cell Biology.

The current study focused on a zebrafish mutant called trilobite. During gastrulation in trilobite embryos, cell motions continue to be disordered and do not develop the same sense of direction and purpose as they do in normal embryos. As a result, trilobite's development is stunted.

The investigators, from Vanderbilt University (Nashville, TN, USA; www.vanderbilt.edu), used positional cloning to demonstrate that trilobite mutations disrupt the Strabismus/Van Gogh protein, which had previously been associated with developing embryos in Drosophila melanogaster. Genetic and molecular analyses suggested that Strabismus/Van Gogh worked to mediate cellular interactions that confer directionality on cell movements during embryogenesis.

Strabismus/Van Gogh was also found to affect the developing brain by influencing migration of motor neurons. The researchers determined that the neurons' method of movement is similar to that of an amoeba: they extend their bodies in the direction they want to move and retract them from the opposite side. By labeling the nerve cells with a fluorescent protein, they showed that the trilobite cells moved much slower and their movements were more random in nature than normal neurons.

This study suggests that the protein Strabismus/Van Gogh acts independently in mediating neuron movement. If this proves to be the case, then it provides "an entry point to elucidate the molecular basis of this class of neuronal migration,” say the researchers.



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