Scientists Found a Bunch of New Eye Color Genes

Scientists Found a Bunch of New Eye Color Genes

In the last few years, we’ve seen scientists make big advancements with organoids — these are clumps of tissues made in the lab that mimic the biology of a full-blown organ. While it’s still a relatively new technique, scientists have been able to make organoids of everything from intestines to lungs and even brain tissue. 

These mini-organs in a dish are models that help us understand the functions of those organs without having to have the full version at hand. And advancing this sequence, scientists have Found a Bunch of New Eye Color Genes.


Tear Gland Organoids

Recently, Dutch researchers publishing in the journal Cell Stem Cell figured out a way to make organoids that resemble tear glands. And weirdly enough, they can actually cry. The scientists started by collecting stem cells from the tear glands of mice and from human participants, and then they grew them with some chemicals known to be involved in eye development. 


Eye Color Genes

Once they had organoids to work with, the next challenge was getting them to cry. Unfortunately, cells in a dish don’t quite have the emotional response to like, Titanic, that we do, so you can’t just show them a movie and hope for the best. 

Neurotransmitter

And so, instead of making an organoid read The Fault In Our Stars, the researchers exposed the tissue to one of the neurotransmitters that cause humans to get all misty-eyed — noradrenaline. Sure enough, when the organoids were exposed to the neurotransmitter, they swelled up with fluid. 


Eye Color Genes_1

But the researchers weren’t done there. They took some of the stem cells made from mice and then deleted a gene called Pax6, which is involved in eye development. Then they raised those cells into tear gland organoids lacking that important gene. These organoids not only grew more slowly but weren’t able to produce tears, which means this gene was crucial for proper tear gland development. 


Ductal Cells

Understanding how these organoids produce tears should help human patients with conditions like Sjögren’s syndrome, an autoimmune disease that leaves the sufferer with dry eyes and mouth. Sjögren's patients tend to have less of the protein made by the Pax6 gene, so this research model should help us study how that affects tear production. 

Ductal Cells

These model tear glands aren’t all the way there yet, though. They’re made of one type of cell: ductal cells. But experiments in mice told the team that they were missing at least one key cell type. So their future work will focus on making more complete models. 

That means we're still a long time away from fully lab-grown tear gland transplants. But the research group is hopeful that their work will lead to a better lab model so that other researchers can study tear-related diseases more accurately. 


New Eye Color Genes

In more eye-related news, an article published last week in Science Advances suggests that the genetics of eye color are way more complex than we imagined. In the paper, an international team of scientists analyzed the genomes of almost two hundred thousand people and identified fifty new genes that are involved in eye color. And that’s a big departure from how you may have learned about the genetics of eye color in school. 

New Eye Color Genes

See, in the past, we thought of eye color as a Mendelian trait. That means a trait governed by just one or a few genes, so it’s easy to predict how that trait will be passed on. If you knew the eye colors of both parents, then you could predict the eye color of the offspring, since the gene for brown eyes was thought to be dominant over the gene for blue eyes. 

But eye color doesn’t just break down into brown, green, or blue. There’s a lot more variation than one gene can account for -- like shades of brown. In fact, previous research had found around a dozen genes linked to eye color. Eye color is still inherited from your parents, but more than one gene is involved. 


Genome-Wide Study

New Eye Color Genes_genome

So in this recent study, the researchers did something called a genome-wide association study — which is a way to capture the influence of a large number of genes across a large population. Then they asked participants to self-categorize their eye color, and if they had brown eyes, to include exactly which shade of brown. 

Now, the vast majority of participants had European ancestry, so they also recruited about sixteen hundred people with Asian ancestry and did the same genetic analysis. All in all, the analysis found fifty genes that influenced which eye color the participant had -- in addition to the ones already known. 

Only eight of these fifty genes had already been associated with some kind of pigmented trait, like hair or skin color. So even though variations in these traits are frequently seen together, like blonde hair with blue eyes, those traits are influenced by different genes. 

The researchers also found that the same genes influence eye color in people of both European and Asian ancestry. Meaning the same genes that influence blue or brown eye color also help determine individual shades of brown. 

So it’s not a simple matter of brown being dominant over blue. Now, there are a few different diseases that involve eye pigmentation — conditions like albinism or pigmentary glaucoma. 

Also Read: How will the world change by 2050? The future of robots

Conclusion

The research group hopes their findings on new eye color genes will help shine some light on how those work and how to treat them. But it also shows us that the simplest things aren’t always as simple as we thought -- and there’s always more to understand about the world and ourselves. 


Article Source: SciShow
Image Source: wikimedia.org

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