Gene of the month - Sonic Hedgehog
If you ask most people what they think of when they hear the words "Sonic Hedgehog", they'll probably describe a spiky blue video game character. But ask a biologist, and they might at least pause for a moment, because as well as being the main protagonist of the 90s Sega games, Sonic Hedgehog is also an important gene found in mammals, along with the similar genes desert hedgehog and Indian hedgehog - both of which were discovered before their showbiz counterpart and are named after real species of hedgehogs rather than cartoons. But why hedgehogs at all?
Like so many genes with wacky names that we'll cover in this series, the original hedgehog gene was first found in tiny fruit flies called Drosophila Melanogaster. Healthy fly embryos are torpedo-shaped, with neat rows of spiky scales called denticles. But fly embryos with a faulty version of the hedgehog gene are short, dumpy and rounded, and completely covered in denticles - much like the spikes that cover a real hedgehog.
In fruit flies, hedgehog is responsible for defining the front from the back of the individual segments that make up a fly embryo, and it's also involved in helping flies to grow wings and other organs. And although mammals like humans don't have wings or make embryos in the same way, the mammalian versions of hedgehog - Sonic, Desert and Indian - are all involved in helping to shape an animal as it grows in the womb. For example, Sonic hedgehog sets up a front-to-back pattern in something called the neural tube - the precursor of the brain and spinal cord - and also helps to form fingers and toes. So despite the comical name - which is probably the closest thing that passed for cool in the scientific world in the 90s - Sonic hedgehog and the rest of his genetic family are vitally important.