"This surprising property of zebrafish blood cells proved to be a tremendous advantage for us because now we can use this technology to examine some of our mutant phenotypes," said Zon. Zon and his colleagues have already used the technique to reveal that carriers of particular mutations which were previously thought to have normal blood cells do in fact have aberrant blood formation.

In the next series of experiments, the researchers inserted genes for either green or red fluorescent proteins into the fish, to distinguish blood cells according to their characteristic fluorescence. "We've been able to put expression of these two fluorescent proteins into distinct blood cell populations, and to use those to visualize how the transplanted cells will actually behave when they're put back into easily visualized animal," said Zon. "We believe that this ability to be highly selective about which populations of blood cells we're analyzing constitutes a tremendous advance for the field."

Zon and his colleagues next used their fluorescent-tagging method to follow the progress of transplants of tagged blood cells into bloodless zebrafish mutants that lack a functioning blood-forming, or hematopoietic, system. After the cells were transplanted, the researchers could easily see precisely how the transplanted cells "rescued" the mutants by restoring their hematopoietic system.

"In our most elaborate experiments, we produced donor fish in which the white blood cells had green fluorescent protein and the red blood cells had red fluorescent protein," said Zon. "Thus, we could follow the course of each of these types of cells as they reconstituted the hematopoietic system of the mutant fish. We found that these mutant animals, which normally died in onl
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
12-Nov-2003