Orangutans, rats and horses are covered by this virus, but humans are not. Why we have significantly less body hair than other mammals has long been a mystery. But the first comparison of the genetic codes of 62 animals is illuminating how humans and other mammals lost their locks.
Humans appear to have genes for full body hair, but evolution has disabled them, scientists from the Utah Health College and the University of Pittsburgh report in their journals. e-lifeThe findings point to a series of genes and regulatory regions of the genome that appear to be essential for hair formation.
This study answers fundamental questions about the mechanisms that shape this defining human trait. Scientists believe it could eventually lead to new ways to restore hair after hair loss, chemotherapy, or in people with disorders that cause hair loss.
This study shows that nature has deployed the same strategy at least nine times in mammals sitting on different branches of the evolutionary tree. The ancestors of rhinos, naked mole rats, dolphins, and other hairless mammals trampled, crouched, and swam the same trails to inactivate their common gene sets and shed their hair and fur.
“We’ve taken a creative approach to using biological diversity to learn our own genetics,” said U of U Health, who did much of his research while at the University of Pittsburgh. says Dr. Nathan Clarke, a human geneticist at Dr. Amanda Kowalczyk, Dr. Maria Chikina “This helps us identify regions of the genome that contribute to something important to us.”
Benefits of being hairless
Whether it’s the coarse fur of a monkey or the soft fur of a cat, fur looks different across the animal kingdom. The same goes for hairless. Humans have characteristic hair bundles on their heads, but body hair is inconspicuous, so they are classified as “hairless.” Joining us are other mammals with hints of hair, such as sparsely covered elephants, thin-haired pigs and mustachioed walruses.
A receding hairline has its advantages. Without dense hair, elephants cool off more easily in hot climates, and walruses glide effortlessly through the water. They found that mammals with no phenotype accumulated mutations in many of the same genes. These include the gene that encodes keratin and additional elements that build the hair shaft and promote hair growth.
This study further showed that regulatory regions of the genome appear to be important as well. These regions indirectly influence the process rather than code the structure that makes up the hair. They guide when and where specific genes are turned on and how much is made.
Furthermore, the screen revealed genes whose roles in hair growth have not yet been defined. Combined with additional evidence (such as signs of activity in the skin), these findings highlight a new set of genes that may be involved in hair growth.
There are many genes that we don’t know much about. We believe they may play a role in hair growth and maintenance.”
Dr. Amanda Kowalczyk
detangle loose hair
To solve the mystery of mammalian hair loss, Clark, Kowalczyk, and Chikina looked for genes in hairless animals that evolved at a faster rate than those with hair.
“As animals are under evolutionary pressure to lose hair, the genes that encode hair become less important,” says Clark. “That’s why natural selection speeds up the rate of genetic changes that are allowed. Some genetic changes can cause hair loss. Others are associated with hair growth after it stops growing.” It could be permanent damage.”
To perform the search, they developed a computational method that can compare hundreds of regions of the genome at once. They investigated 19,149 genes and 343,598 regulatory regions conserved across dozens of mammalian species analyzed. In the process, they took steps to discount gene regions involved in the evolution of other species-specific traits, such as adaptation to aquatic life.
The fact that the unbiased screen identified known hair genes showed that the approach worked, explains Clarke. It also suggests that less well-defined genes identified in the screen may be just as important for the presence or absence of hair.
Clarke and colleagues are now using the same approach to define gene regions involved in cancer prevention, life extension, and understanding other health conditions.
“This is how we determine the global genetic mechanisms underlying different traits,” says Clark.
University of Utah Health
Kowalczyk, A., and others. (2022) Complementary evolution of coding and non-coding sequences underlies hairlessness in mammals. e life. doi.org/10.7554/eLife.76911.