I'm thrilled to announce that our paper on hair colour genetics has been published today:
rdcu.be/bdawY
This was a great collaboration, and used the amazing @uk_biobank
So what did we find? (thread)
rdcu.be/bdawY
This was a great collaboration, and used the amazing @uk_biobank
So what did we find? (thread)
Firstly, we know you need 2 mutations in the MC1R gene to have red hair. When we looked in UKBiobank we found that some people with red hair only had 1 known mutation, so we went looking for more. We found 3 rare mutations which increased the probability of red hair a lot.
But there were still 6% who only had one mutation. We had a look if other genes affect if you have red hair, and found some that hadn't been linked before. One of them encodes the protein that binds to MC1R, alpha-MSH, and another that blocks MC1R, called ASIP.
That still didn't explain everything, so we had a look for interacting genes - epistasis. This is notoriously hard to detect, but with a very large N you're in with a shot. We found that some genes interact preferentially with particular MC1R mutations, the weakest ones.
One of these is ASIP. That means that some people have keratinocytes that make more ASIP, which binds to MC1R on their melanocytes and stops it from signalling - if this happens enough then they make pheomelanin - the pigment that causes red hair!
We also looked at other hair colours, and found that 100's of genes are linked to blond and brown hair - that means they are polygenic, unlike red hair colour. In fact, the spectrum goes from black hair all the way to blond.
Finally, there's one little twist. Whilst you need 2 MC1R mutations to have red hair, it's not guaranteed. We found that most people with 2 MC1R mutations don't actually have red hair. That means there are probably more examples like ASIP that mask the effects of mutations.
This was a fantastic collaboration with some great people: @GroupTenesa @erolaPC @reestheskin Ian Jackson (not on Twitter) and supported by @mrc_hgu and @CGAT_Oxford Last but not least, the participants of @uk_biobank who have devoted their time and biological material, thanks!
