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A Gene Called ‘Sonic Hedgehog’ Is Behind the Weirdest Coronavirus Symptoms

Even more intriguing is why scientists named a gene after Sonic in the first place

As the number of coronavirus cases increases exponentially, a peculiar new symptom has appeared: the temporary loss of your senses of smell and taste. This unusual symptom has been reported by doctors around the globe, and tales of scentless, tasteless days of sickness have been spreading rapidly on social media. In the past couple of weeks, professional basketball player Rudy Gobert and famous fashionista Arielle Charnas, among others, have described their absent senses of smell and taste to their interweb audiences.

One proposed explanation for these adjourned senses: the silencing of a gene called, um… Sonic Hedgehog. Last week, Harvard genetics professor David Sinclair suggested by tweet that the coronavirus could suppress the uniquely named Sonic Hedgehog gene, resulting in “a loss of signaling factors that cause stem cells to divide in the tongue and nose,” and all I can think about are those nightmarish chompers, ugh.

Unnerving, chilling, awful teeth aside, I have all kinds of questions: What does the Sonic Hedgehog gene do? How does the coronavirus impact the Sonic Hedgehog gene? And, of course, why the hell would someone name a gene Sonic Hedgehog?

First, what it does: The Sonic Hedgehog gene arranges for the creation of an important protein, which also happens to be called Sonic Hedgehog and primarily helps with early development. According to the National Library of Medicine, “Sonic Hedgehog plays a role in cell growth, cell specialization and the normal shaping (patterning) of the body. This protein is important for development of the brain and spinal cord (central nervous system), eyes, limbs and many other parts of the body.” As Sinclair noted, Sonic Hedgehog also controls the proliferation of adult stem cells, which normally support our senses of smell and taste, among other things.

To that end, there have been some studies suggesting that Sonic Hedgehog plays a role in multiple sensory systems (beyond just smell and taste), and that a shortage of Sonic Hedgehog could result in a temporary loss of these senses, as some coronavirus patients have been experiencing. Moreover, previously known coronaviruses have been shown to cause changes in smell, so it makes some sense to suggest that Sonic Hedgehog could be at play here.

However, definitively saying that Sonic Hedgehog is the reason for this scentless, tasteless symptom would be jumping the gun. One recent study suggests that the coronavirus could infect cells in the nose, including stem cells, which would lead to an altered sense of smell, while some professionals have said that the virus could simply trigger localized inflammation in the nostrils that could impede your sense of smell (and subsequently, your sense of taste) as happens to a lesser extent any time you get a bad cold.

Some scientists have also suggested that the coronavirus could infiltrate the olfactory bulb, the brain region where cells in the nose send smell information. Again, previously known coronaviruses have been shown to penetrate the olfactory bulbs of mice, and other papers have suggested that they could do the same in humans, so this hypothesis holds some water, too. Really, though, none of these theories — not even Sonic Hedgehog — have enough data behind them yet to say for sure.

Now, as for how the Sonic Hedgehog gene got its name, you might be surprised to learn that there are multiple variations of the Hedgehog gene, including the Desert Hedgehog and Indian Hedgehog. These Hedgehog genes earned their names because a mutation of the gene causes fruit fly embryos, in which they were first discovered, to be covered with denticles, projections that resemble the spikes on a hedgehog. 

The idea at first was to name each variant of the Hedgehog gene in humans after a species of real hedgehogs, hence the Desert Hedgehog and Indian Hedgehog. But then Robert Riddle, a postdoctoral researcher who was working in the Harvard lab where they were looking into these genes, decided to name this particular variant after Sonic the Hedgehog, reportedly after eyeing a Sonic comic book that his daughter had. Because there are so many genes out there, memorable names can help scientists tell them apart. This whimsical name in particular has since caused some quarrels among more serious scientists, but YOLO.

Amusing names aside, hopefully scientists will realize that, like Sonic, they gotta go fast and figure out why the coronavirus is causing people to lose their senses, which would hopefully bring us one step closer to figuring out how to deal with this pandemic. And if they need some music to encourage them, we have just the thing.

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