Here Today, Gone Tomorrow: How Humans Lost The

Detangling the progression of hair loss

image: A first-of-its-kind study comparing the genomes of 62 mammals answers fundamental questions about the mechanisms that underlie a defining human characteristic: paucity of body hair.
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Credit: Lucas

(Salt Lake City) – Orangutans, mice, and horses are covered in it, but humans aren’t. Why we have so much less body hair than most other mammals has long been a mystery. But a first-of-its-kind comparison of genetic codes from 62 animals is beginning to tell the story of how people — and other mammals — lost their locks.

Humans seem to have the genes for a full coat of body hair, but evolution has held them back, according to scientists at V University of Utah Health A University of Pittsburgh report in the Journal eLife. The results point to a set of genes and regulatory regions of the genome that appear to be essential for hair making.

The research answers fundamental questions about the mechanisms that shape this defining human characteristic. Scientists think it could eventually lead to new ways to restore hair after alopecia and chemotherapy — or in people with disorders that cause hair loss.

The study goes on to show that nature has used the same strategy at least nine times in mammals that sit on different branches of the evolutionary tree. The ancestors of rhinos, naked mole rats, dolphins, and other hairless mammals trampled, squashed, and swam along the same path to disrupt a common set of genes in order to shed their hair and fur.

“We have taken a creative approach to using biodiversity to learn about our genes,” he says. Nathan Clark, Ph.D., a human geneticist at U of U Health who did a lot of research while at the University of Pittsburgh with Amanda Kowalczyk Ph.D., and Maria Cekina Ph.D. “This helps us identify regions of the genome that contribute to something important to us.”

Benefits of hair loss

Whether talking about the coarse body hair of a monkey or the smooth fur of a cat, hair looks different across the animal kingdom. The same goes for baldness. Humans have a distinct tuft of hair on our heads, but because body hair is less visible, we fall into the “hairless” category. We are joined by other mammals with hints of hair such as elephants with their sparse mantle, hooded warthogs, and mustachioed walruses.

There are benefits to a receding hairline. Without thick hair, elephants cool more easily in hot climates and walruses glide through water easily. Despite the diverse causes, Kowalczyk’s analysis found that these and the other hairless mammals analyzed had accumulated mutations in many of the same genes. These include the genes that code for keratin, additional elements that build the hair shaft and facilitate hair growth.

In addition, the research showed that regulatory regions of the genome appear to be equally important. These regions do not encode the structures that make hair but influence the process indirectly. They direct when and where specific genes are turned on and how much they are produced.

Furthermore, the screen revealed genes whose role in hair germination had not been identified. Together with additional clues – such as markers of activity in the skin – these findings highlight a new group of genes that may be involved in hair growth.

“There are quite a few genes that we don’t know much about,” Kowalczyk says. “We think they could have a role in hair growth and maintenance.”

Detangling hair loss

To decipher the mystery of hair loss in mammals, Clark, Kowalczyk, and Cecchina looked for genes in hairless animals that evolved at faster rates than their counterparts in hairy animals.

“As animals are under evolutionary pressure to lose hair, the genes that encode hair become less important,” says Clark. This is why the rate of genetic changes allowed by natural selection has accelerated. Certain genetic changes may be responsible for hair loss. Others may be collateral damage after the hair stops growing.”

To carry out the research, they developed computational methods that can compare hundreds of regions of the genome at once. They surveyed 19,149 genes and 343,598 regulatory regions that were conserved across the dozens of mammalian species analyzed. In the process, they took steps to exclude genetic regions responsible for the development of other species-specific traits, such as adaptations to aquatic life.

The fact that the unbiased screen identified known hair genes demonstrated the success of this approach, Clark explains. It also suggests that genes identified in the screen that are less obvious could be just as important for having hair — or not having it.

Clark and his colleagues are now using the same approach to identify genomic regions involved in preventing cancer, prolonging life, and understanding other health conditions.

“This is a way to identify the global genetic mechanisms underlying different characteristics,” Clark says.

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The research was supported by the National Institutes of Health and is published as “.Complementary evolution of coding and non-coding sequences underlies mammalian baldness. “

About University of Utah Health

University of Utah Health Provides compassionate, compassionate pilot care to a referral area that includes Idaho, Wyoming, Montana, and much of Nevada. A center for health sciences research and education in the region, U of U Health has a $458 million research institution and trains the majority of physicians and health care providers in Utah in the Colleges of Health, Nursing, and Pharmacy, and the Colleges of Dentistry and Medicine. With more than 20,000 employees, the system includes 12 community clinics and five hospitals. U of U Health is nationally recognized as a transformative healthcare system and provider of world-class care.

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