Thursday, March 01, 2007

Dig facial hair?   posted by p-ter @ 3/01/2007 05:54:00 PM

Nature this week has a news feature on research done by Angela Christiano into the genetics of various hair-related phenotypes:
[F]or Christiano, hair is not just an adornment. It is a filament that binds together her appearance, her family, her personal life and her work. Descended from two generations of hairdressers, she came to appreciate hair's true importance when her own locks began to fall out in an episode of alopecia areata. Working at Columbia, she immediately shifted the focus of her research from skin disease to hunting down the genes that underlie human hair disorders, such as an atavistic condition in which people sprout thick hair all over their faces. Her scientific work may even end up with a cosmetic use, saving men and women with normal but nevertheless unwanted hair from shaving, waxing and depilation.
I'd never heard of any of the disorders mentioned in the article, but the references are fascinating. There's the alopecias (a type of which is shown in the bottom picture), one of which is caused by a recessive mutation in a transcription factor. Then there's hypotrichosis, in which hair can grow, but breaks off near the head. This disorder seems to be caused by mutation in a gene encoding for cell adhesion. She also discovered the gene that causes a rare disorder in which the affected individuals have no nails on their fingers or toes.

As for the hairy-faced individual in the top picture, the causal mutation is currently unknown, though it seems to be an X-linked recessive trait:
One of Christiano's most intractable puzzles is in her "Mexican hair people", who have thick, 'terminal' hair all over their faces rather than the finer 'vellus' hair, which is normal. Christiano and her team have spent more than five years studying one of the only reported cases of a family with this disorder - called hypertrichosis4. But although they sequenced 82 genes in the relevant region of the X chromosome and every snippet of microRNA, they could not find a causative mutation. Some kind of genetic trickery could be afoot: perhaps a mutated RNA outside the protein-coding genes is failing to regulate a gene on another chromosome.