Gene Expression

Why is hair kinky?

I saw this paper in Nature Genetics, Disruption of P2RY5, an orphan G protein-coupled receptor, underlies autosomal recessive woolly hair:

The genetic determinants of hair texture in humans are largely unknown. Several human syndromes exist in which woolly hair comprises a part of the phenotype; however, simple autosomal recessive inheritance of isolated woolly hair has only rarely been reported…In all cases, we discovered pathogenic mutations in P2RY5, which encodes a G protein-coupled receptor and is a nested gene residing within intron 17 of the retinoblastoma 1 (RB1) gene. P2RY5 is expressed in both Henle’s and Huxley’s layers of the inner root sheath of the hair follicle. Our findings indicate that disruption of P2RY5 underlies ARWH and, more broadly, uncover a new gene involved in determining hair texture in humans.

Disease loci can tell us a lot about the normal range of human variation; the blue-eye gene was originally implicated in a form of albinism. So I got curious and popped P2RY5 into Haplotter, which detects recent selection events. Here’s what I found….

Here’s iHS:

i-ff206fca9e0cfa9c6bc9f5c6aafa732b-iHS.gif

And H:

i-f30704ff239972d21dbd9d16eada2bb2-Het.gif

Looks like there’s some action going on here. We’re looking at Yoruba (YRI), European (CEU) and East Asian groups (ASN) if you didn’t know. Here’s the table which shows p-values in the genomic region around this locus:

Genes in the region


Gene ID Name Region CEU YRI ASN
8803 SUCLA2 46314792 – 46373463 0.093768 0.011064 0.359281
55270 NUDT15 46409704 – 46419283 0.093768 0.005330 0.359281
29079 MED4 46448093 – 46467241 0.117392 0.015274 0.539616
9445 ITM2B 46602310 – 46634228 0.999955 0.300291 0.999954
5925 RB1 46675912 – 46854023 0.999955 0.021859 0.999954
10161 P2RY5 46783275 – 46787947 0.999955 0.021814 0.539616
1102 RCBTB2 46861100 – 46905317 0.999955 0.036685 0.539616
57105 CYSLTR2 47078952 – 47081499 0.541838 0.999955 0.999954
9206 RAD17P2 47415974 – 47418931 0.999955 0.225666 0.539616

I’ll let you figure out what’s going on with NUDT15….

Related: EDAR controls hair thickness.

Comments

  1. #1 El Christador
    February 27, 2008

    Hair kinky?

    I think that’s subjective. Lots of us aren’t into that.
    :P

  2. #2 kezdro
    February 27, 2008

    Interesting – but would you mind using graphs that are legible (.png may – or may not – help there)? Or linking to full-size versions?

    Maybe something more after I figure out iHS and H..

  3. #3 razib
    February 27, 2008

    http://hg-wen.uchicago.edu/selection/haplotter.htm

    just type in the gene name to the left.

  4. #4 Richard Simons
    February 27, 2008

    I was once suckered into giving a course on animal ecophysiology (I was told it was basic ecology until after it was too late to back out) which was a traumatic experience as I’ve only taken one university-level animal physiology course in my life. One of the students asked what the advantage is of kinky hair. I wondered if it might be a better insulator against the heat of the sun but that’s just guessing. I also said that perhaps the question should be the other way round – why do people have straight hair. Perhaps to shed rain more readily? I was hoping this post would answer the question. Are there any suggestions?

  5. #5 razib
    February 27, 2008

    I was hoping this post would answer the question. Are there any suggestions?

    100:1 odds that it has nothing to do with hair form as such. the variation in hair follicle thickness is due to a gene which is implicated in lots of developmental wackiness (see the EDAR link).

  6. #6 Niobe
    February 28, 2008

    Perhaps straight hair gave us an advantage when we moved to cooler climates and huddled together in fur clothing, so lice and fleas wouldn’t drive us crazy. Of course lice evolved along with our straight hair.

    Now I find it odd / interesting that our body hair (genital, torso / limbs for men, armpits) didn’t go along with the smooth hair transition.

  7. #7 agnostic
    February 28, 2008

    It’s either pleiotropic, and selection was for its effect on something else, or — what we would predict from Orr — selection acted on its effects at a bunch of places. It’s best if an allele helps adapt a population to a new environment by improving fitness through multiple phenotypes. There’s a new paper on adaptation in sticklebacks that shows this.

    As for EDAR, at least one reason for selection was body odor — it’s involved in sweat glands. East Asians have an independent mechanism for suppressing body odor (the dry earwax allele), and common factors are never a coincidence. Now why East Asians were selected to not stink, I have a little hypothesis about…

  8. #8 razib
    February 28, 2008

    Now why East Asians were selected to not stink, I have a little hypothesis about…

    oh, i bet you do assman….

  9. #9 Richard Simons
    February 28, 2008

    Razib, thanks. It should have occured to me that a gene could have several different effects.

  10. #10 agnostic
    February 28, 2008

    oh, i bet you do assman….

    It doesn’t have to do with sex, attraction, or asses, if that’s what you were thinking…

  11. #11 Sandgroper
    February 29, 2008

    It doesn’t have to do with reality either.

    Anyone who thinks East Asians don’t stink hasn’t been in the middle of a bunch of them who haven’t washed for a few days.

  12. #12 Luis
    March 2, 2008

    “I’ll let you figure out what’s going on with NUDT15….”

    Epicanthic fold?