So there’s still more to figure out.
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We all know the phrase “you can have too much of a good thing” - and this applies to vitamin D too. If kids don’t get enough vitamin D, their bones won’t develop normally, and they’ll get a disease called rickets. But when countries started adding a lot of vitamin D to children’s food to try to prevent rickets, doctors learned that some kids also got sick from having too much vitamin D. And figuring out why those kids got sick took decades.
By the 1950s in Britain, fortification of infant formula and milk led to infants getting up to 4,000 international units of vitamin D per day - which is way out of proportion with kids’ actual needs. This led to 204 cases of infants with dangerously high levels of calcium. In 2011, researchers identified a mutation in a gene called CYP24A1 which stops the body from breaking down excess vitamin D. But further research showed that, of people with infant hypercalcemia, about 10% don’t actually have that mutation. So there’s still more to figure out. To understand why it doesn’t make sense for a single, clear-cut genetic mutation to cause a disease most of the time, it helps to understand what a gene is. Genes are instructions for making proteins, which are essential for everything in the body, from pulling muscles to breaking down food to allowing neurons to fire. Even though 98% of the genome does not code for proteins, it is not just there for decoration. For example, there are flags in the code on either side of every gene that mark the beginning and end. The flag on one end, the 3’ end, affects the shape of the resulting messenger RNA molecule. When the 3’ end is mutated, the folds get thrown off and the mRNA cannot do what it needs to do. This is what researchers found when they analyzed blood samples from 6 patients with unexplained hypercalcemia.
The study, published in 2023, showed that, in these patients, the protein-coding part of the CYP24A1 gene was fine, but mutations in the 3’ end of the gene meant that the mRNA was misfolded, and the protein couldn’t do its job. This is an example of how the 98% of DNA that doesn’t get turned into protein can directly matter in people’s lives.
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