Today’s guest post was contributed by Allessandra DiCorato, a freelance science writer based in Vancouver, British Columbia. Read more of her work at allessandradicorato.com.

When the last ice age ended thousands of years ago, a small marine fish called the stickleback began colonizing new freshwater habitats. Fish in different environments developed distinct features, evolving into a wide array of diversity that scientists still study today. Over the last two decades, researchers have identified components of the genome that control different parts of the stickleback’s skeleton: how many spines a fish has near its dorsal fin, the size of its pelvis, and the patterns of protective bony “armor” plates on its flanks. 

Now, scientists are looking deeper into the internal structure of stickleback bones, hoping to shed light on the genetic basis for human diseases.

In a new analysis in G3: Genes|Genomes|Genetics, researchers from the Stanford School of Medicine have uncovered genetic regions linked to variation in traits such as bone porosity and thickness. 

To match physical characteristics with the genetic regions that may cause them, the researchers studied more than 100 offspring produced by two fish: a wild threespine stickleback from a marine environment off the coast of California and one from a freshwater lake in British Columbia. With a high-resolution X-ray imaging technique called micro-computed tomography, they mapped the skeleton of each animal and measured a range of bone traits. 

Next, the researchers used arrays, which detect genetic variation, and quantitative trait locus mapping, a statistical approach that helps draw connections between genes and complex traits,  to pinpoint regions of the genome that influence the internal structure of the sticklebacks’ bones. They identified a region that influenced the surface area, volume, and pore size of armor plates, as well as other regions affecting the porosity of vertebrae. In humans, decreased bone porosity can be a sign of osteoporosis, but the authors say that it could help sticklebacks adapt to different environments, such as freshwater, where it may be beneficial to have a skeleton that is less dense.

For many other traits, the researchers did not identify significant genetic associations. This could be because they are controlled by many different genes. But about 8% of the fish offspring had “ivory vertebrae”—abnormally thick bones—which were strongly associated with part of chromosome 17. This region contains the Tnfrsf1b gene, a stickleback parallel of a human gene known to increase susceptibility for Paget’s disease, a condition involving abnormal bone remodeling.

The findings suggest that sticklebacks may be valuable models not only for studying the evolution of traits, but also for understanding skeletal diseases in other animals.

References

  • Behrens VC, Lee D, Wucherpfennig JI, and Kingsley DM. Genetic analysis of bone morphometry and ivory vertebrae in threespine stickleback. G3: Genes|Genomes|Genetics. 2026; jkag164, https://doi.org/10.1093/g3journal/jkag164

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