It’s clear from the wacky names assigned to certain genes—“lunatic fringe,” “faint sausage,” “sex lethal”—that scientists have a sense of humor. They’re so named in order to make these genes unique and memorable, helping them to stand out among many other discoveries. It’s one thing to name genes things like “dreadlocks” and “clown” when talking about fruit flies, but it’s a different story when those genes are linked to developmental disorders in humans. That’s where the “Sonic Hedgehog” gene comes in.
In brief, genes are sections of code that act as blueprints for building proteins. Mutations in a gene—changes in the code sequence—can alter the proteins and cause drastic effects on the overall organism. In the early 1990s, Christiane Nsslein-Volhard (who would go on to win a Nobel Prize in Medicine in 1995) discovered a gene that, when deactivated, caused small pointy growths called denticles to sprout on fruit flies. Since the gene’s mutation resulted in what looked like little quills, she named this gene hedgehog. Three similar genes were eventually discovered, the first two being named after real hedgehog species (Indian hedgehog and Desert hedgehog), but the third was named after Sega’s mascot, thanks to post-doc Robert Riddle. He took inspiration from the spiky-headed character in his daughter’s promotional comic book brought over from the U.K. before the video game was released in the U.S. The name would stick as Sonic’s popularity skyrocketed, but that came with unforeseen consequences.
“Sonic Hedgehog,” or the SHH gene, also appears in vertebrates, including humans, and is much more vital to development than its name might suggest. The gene codes for a similarly named protein “Sonic Hedgehog,” which acts as a chemical signal that’s essential to developing embryos. It plays a role in cell growth, what those cells do when grown, the normal shaping of the body, and development of the brain and spinal cord, eyes, limbs, and numerous other body parts. Specifically, it’s necessary for the development of the forebrain and is one of the signaling proteins needed to form the right and left hemispheres of the brain.
A mutation in this gene—of which over 100 were found—can cause nonsyndromic holoprosencephaly, an abnormality of brain development that also affects the head and face, and ranges from mild to severe. The most severe cases result in cyclopia (one central eye) and cause death before or soon after birth. Not so funny anymore, which is why the Human Genome Organization’s Nomenclature Committee added it to their list of the 10 genes that needed to be renamed in response to physicians’ concerns about “inappropriate, demeaning and pejorative” names.
That was in 2006, but “Sonic Hedgehog” is still the gene’s official name today.