Leonard Zon and his colleagues at the Harvard Medical School were trying to find out how hemoglobin forms by studying zebrafish, small piscians whose transparent bodies allow their inner workings to be easily seen while they are alive. The effort centered on a mutated strain of fish known as “shiraz.” The researchers name their mutants after red or white wines, depending on whether red or white blood cells are involved. The shiraz fish lacks hemoglobin, the molecule that binds with oxygen in the cells of all red-blooded animals. Other mutants have names such as “chianti” and “chardonnay.”
The zebrafish is so important to researchers that its genome has been sequenced along with that of humans. Zon and his team used this information to find and clone the gene that makes shiraz so pale. The gene has a less fun name, glutaredoxin 5, or grx5 for short.
More scientific detective work revealed that yeast has its own version of the same gene. That’s strange because yeast doesn’t have blood, so it doesn’t need hemoglobin. But yeast does need iron and its grx5 gene is involved in manipulating iron in this fungus, best known for making beer and wine.
Zon and his team then made a mutant zebrafish with a doctored rendering of the yeast gene. “That rescued the fish,” Zon declares. “It could now make hemoglobin. Without hemoglobin, zerbrafish embryos lacking grx5 can absorb oxygen from water through their skin. But eventually they die, most likely from their anemia.”