eLife: How humans lose body hair

Orangutans, rats and horses are there, but humans are not
.
Why humans have significantly less body hair than other mammals has been a mystery
.
But the first comparison of the genetic codes of 62 animals begins to tell the story
of how humans and other mammals lost their locks.

Scientists at the University of Utah School of Health and the University of Pittsburgh report in the journal eLife that humans appear to have genes for full-body hair, but evolution has rendered them dysfunctional
.
The findings point to a set of regulatory regions of genes and genomes that appear to be essential
for hair formation.

This study answers fundamental questions
about the mechanisms that form this defining human trait.
Scientists suspect that this could eventually lead to hair loss and new ways to restore hair after chemotherapy, or patients
with diseases that cause hair loss.

This study further suggests that nature deployed the same strategy
at least 9 times in mammals located in different branches of the evolutionary tree.
The ancestors of rhinos, naked mole rats, dolphins and other hairless mammals pedaled, dived and swam along the same path, disabling a common set of genes to shed hair
.

"We took a creative approach and used biodiversity to understand our own genes, which helped us identify regions
of the genome that contribute to what is important to us.
"

Benefits of being hairless

Whether it's the coarse body hair of a monkey or the soft fur of a cat, in the animal kingdom, the hair looks different
.
The same goes for
hair loss.
Humans have a unique handful of hair on their heads, but because body hair is not very conspicuous, we belong to the "hairless" category
.
We are joined by other mammals with a small amount of hair, such as elephants with sparse hair, pigs with sparse hair, and walruses
with mustaches.

Receding hairline is beneficial
.
With no bushy hair, elephants cool down more easily in hot climates, and walruses glide effortlessly through the water
.
Despite a variety of causes, Kovalczyk's analysis found that these and other hairless mammals analyzed accumulated mutations in many of the same genes
.
These genes include genes that code for keratin, as well as other elements
that build the hair shaft and promote hair growth.

The study also showed that the regulatory regions of the genome seem to be equally important
.
These areas do not encode the structure that produces the hair, but indirectly influence the process
.
They guide when and where certain genes are turned on, and how much
is produced.

In addition, the screening also found that genes that play a role in hair germination have not yet been identified
.
Combined with other evidence, such as signs of active skin, these findings highlight a new set of genes
that may be involved in hair growth.

"There are a lot of genes that we don't know much about
.
We think they may play a role
in hair growth and maintenance.
”

Solve hair loss problems

To solve the mystery of mammalian hair loss, researchers looked for genes
in hairless animals that evolved faster than hairy animals.

"Because animals lose hair under evolutionary pressure, the genes that code for hair become less important
.
" "That's why they accelerate the rate
of genetic change allowed by natural selection.
" Some genetic changes can be the cause of
hair loss.
Others may be collateral damage
after hair growth stops.
”

To conduct the search, they developed computational methods that can compare hundreds of regions
of the genome simultaneously.
They investigated 19,149 genes and 343,598 regulatory regions
in the dozens of mammalian species analyzed.
In the process, they took steps that ignored the genetic regions responsible for evolving traits unique to other species, such as adaptation to aquatic life
.

The authors explain that this unbiased screening identified known hair genes, which proves that this approach works
.
It also suggests that those less well-defined genes identified in the screen may be just as important
as having hair or not having it.

Researchers are now using the same method to define genetic regions
involved in cancer prevention, longer lifespan and understanding of other health conditions.

"This is a way to
determine global genetic mechanisms under different traits.
"