Do you sneeze when you look at a bright light? This gene might explain why
Humans throughout history have tried to understand the meaning behind a sneeze. Homer’s Odyssey proposed that a sneeze was a good omen, a viewpoint shared by the Greeks, Romans, and many pagan cultures1. On the other hand, some cultures considered a sneeze to be a sign of impending doom, which was reinforced by the spread of the black plague. A more modern understanding has taught us that sneezing is actually a defense mechanism, capable of ejecting potential toxins or infectious agents out of the nasal cavity at speeds exceeding 100 miles per hour2.
Anyone who’s had allergies knows that a number of airborne molecules can induce a sneeze, but one of the more mysterious of triggers is sunlight. Patterns have been observed that suggest a genetic factor contributes to this light-induced response, and a specific change in the DNA near the ZEB2 gene might be involved.
A number of researchers have explored the phenomenon of light-induced sneezing, also known as “photic sneeze.” Preliminary evidence suggests that sunlight-induced sneezing may be inherited and lead to the description of ACHOO syndrome—yes, ACHOO syndrome, which stands for Autosomal Dominant Compelling Helio-Ophthalmic Outburst Syndrome3. These early indications are reinforced by a study using self-reported data in 2010 that indicated a single nucleotide polymorphism (a SNP, a change at a single position in the DNA sequence) near the ZEB2 gene may be involved4.
ZEB2 is a very important gene because the protein it codes for controls many important developmental processes, particularly those involving neuronal development5. However, the single base pair change associated with ACHOO syndrome is located between ZEB2 and another gene involved in organ development4,6. It’s not clear exactly how this change can lead to the photic sneeze response, but research has suggested that ACHOO syndrome occurs when neurons misfire3,4,7. Thus ZEB2’s involvement in neuronal development makes it a strong candidate behind the observed association with the photic sneeze reflex.
The link between sunlight-induced sneezing and neurons has been suggested by multiple research studies3,4,7. The concept is that overstimulation of neurons in the eyes by a bright light will lead to misfiring of neurons in the brain, which ultimately leads to a sneeze. It’s also possible that sudden bright light stimulation leads the brain to respond with a non-specific flurry of signals (a little bit like smashing buttons on a keyboard instead of typing a cohesive message) that activates numerous neurons which go to places like the eyes and nose.
Though it’s not clear how this reflex develops, studies have shown that 15-35% of some populations experience photic sneezing! Some DNA tests found in the Helix Store, including BABYglimpse by HumanCode and products from DotOne, already include an assessment of the DNA near ZEB2—so if the sun makes you achoo!, you might be able to find that your own genetics play an important role.
2Kulas, Philipp, et al. “Investigations on the prevalence of the photo-Induced sneezing reflex in the German population, a representative cross-Sectional study.” European Archives of Oto-Rhino-Laryngology, vol. 274, no. 3, 2016, pp. 1721–1725., doi:10.1007/s00405-016-4256-2. Web. 15 Nov. 2017.
3Langer, Nicolas, Gian Beeli, and Lutz Jäncke. “When the Sun Prickles Your Nose: An EEG Study Identifying Neural Bases of Photic Sneezing.” Ed. Björn Brembs. PLoS ONE 5.2 (2010): e9208. PMC. Web. 15 Nov. 2017.
4Eriksson, Nicholas et al. “Web-Based, Participant-Driven Studies Yield Novel Genetic Associations for Common Traits.” Ed. Greg Gibson. PLoS Genetics 6.6 (2010): e1000993. PMC. Web. 15 Nov. 2017.
5Hegarty, Shane V., et al. “Zeb2: A multifunctional regulator of nervous system development.” Progress in Neurobiology, vol. 132, 2015, pp. 81–95., doi:10.1016/j.pneurobio.2015.07.001. Web. 15 Nov. 2017.
6Wu, San-Pin et al. “Choose Your Destiny: Make A Cell Fate Decision with COUP-TFII.” The Journal of steroid biochemistry and molecular biology 157 (2016): 7–12. PMC. Web. 15 Nov. 2017.
7Hydén, D, and S Arlinger. “On light-Induced sneezing.” Eye, vol. 23, no. 11, Mar. 2009, pp. 2112–2114., doi:10.1038/eye.2009.165.
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