Those who favor white meat over dark meat at the holiday dinner table can savor a delicious prospect. Now that scientists have found a gene that determines muscle fiber type in zebrafish embryos, can all-white-meat turkeys really be far behind? Well, yes. But the discovery still represents an advance in developmental biology.
In growing zebrafish embryos, all precursor muscle cells are preprogrammed to become fast-twitch muscle, better known to turkey aficionados as white meat. Only a signal from a protein named Hedgehog turns them into darker, slow-twitch muscle. But Hedgehog does many things in development, and geneticist Philip Ingham of the University of Sheffield, U.K., and colleagues wanted to track down the particular protein that Hedgehog stimulates in muscle to make slow-twitch muscle.
The team sifted through a collection of mutant zebrafish, looking for one that didn't make slow-twitch muscle correctly. When they found one, they sequenced the gene involved. It turned out to encode a protein called Blimp-1, which is best known for turning certain immune system cells into antibody-producing cells. When the team examined zebrafish lacking Hedgehog, they found that the fish lacked Blimp-1--and slow-twitch muscle. But when they gave these fish a Blimp-1 boost, they regained the ability to make slow-twitch fibers, they report 21 December in Nature Genetics.
"We haven't had any information until now about what Hedgehog signaling does" to generate muscle types, says developmental biologist Stephen Devoto of Wesleyan University in Middletown, Connecticut. Alas, the study doesn't provide a clearcut path to engineering an all-white-meat turkey, says Ingham. Even though blocking Blimp-1 early in development might stop white meat from turning dark, other switches such as exercise or neural stimulation can convert white meat to dark in older animals, he says.