Every day is a good hair day for mice. They enter the world pink and naked, but within a week they're covered head to toe in a silky-smooth pelt with every hair perfectly oriented. Now scientists think they've figured out just how this happens--a finding that could explain the orderliness of other animal features such as feathers and scales.
Growing a flawless coat is a pretty neat trick: millions of hairs must emerge at just the right angles along the skin to lay down and follow every curve of the body. But just where does this order come from? A useful model for answering that question is the Frizzled6 mouse, a mutant breed born with permanently messy hair. These rumpled rodents lack a gene called fz6, resulting in patches of cowlicks and whorls.
To figure out what goes wrong in these mice, a team led by Jeremy Nathans, a molecular biologist at Johns Hopkins University School of Medicine in Baltimore, Maryland, examined the skin of newborn Frizzled6 and normal mice under a microscope each day as their first hairs grew in. The researchers recorded the orientation both of the follicles--the base of the hair inside the skin--and of the hair shafts emerging from the surface.
The reason for Frizzled6 mice's messy hair soon became obvious: The mutant mice are born with hair follicles that point in random directions, while normal mice have follicles pointing more or less in the direction needed for the hair to lay flat. As the hairs grow, their follicles orient themselves to minimize differences with their neighbors. In normal mice, this results in perfectly aligned fur. But in Frizzled6 mice, the randomly oriented hairs locally organize into whorls and tufts, the team reports online this week in Proceedings of the National Academy of Sciences. Considering that fz6-related genes are conserved between species, the same self-organizing system likely "applies to all mammals, and also to bird feathers and fish and reptile scale orientation," Nathans says.
"What's most interesting is how the follicle cells might be sensing each other," says Gary Struhl, a molecular biologist at Columbia University, who works on a similar system in flies. A simpler system to study this might be the hairs of the inner ear where follicles are much smaller and closer together, he notes.
Related site
)
)
)
)
)
)
)
)
)
