Why do people go bald? Genetic discovery reveals why humans are hairless mammals

SALTY LAKE CITY, Utah — Why don’t humans have as much hair as other mammals? From mice and horses to orangutans and chimpanzees, all other mammals display impressive layers of fur, or hair, so why not us? Fascinating new findings from a team at the University of Utah are finally providing some much-needed answers.

A first-of-its-kind comparison of genetic codes spanning 62 different animals revealed that humans still have all the genes needed to sport a full layer of body hair, but evolution appears to have “turned off” those specific genes. Specifically, this project targets a set of genes and regulatory regions of the genome essential for hair formation. The study authors hope that this work will one day lead to new ways to regrow hair after baldness as a result of chemotherapy or disorders that cause hair loss such as alopecia.

Interestingly, the study notes that nature has used the same evolutionary strategy in at least nine other mammals that reside on various branches of the evolutionary tree. The ancestors of rhinos, naked mole rats, dolphins, and other hairless mammals seem to have followed the same path to turn off a common set of genes, resulting in hair and fur loss.

“We’ve taken the creative approach of using biological diversity to learn about our own genetics,” says Nathan Clark, Ph.D., a human geneticist at the University of Utah, in a Press release. “This is helping us identify regions of our genome that contribute to something important to us.”

Clark conducted much of the research while at the University of Pittsburgh with investigators Amanda Kowalczyk, Ph.D., and Maria Chikina, Ph.D.

Mystery genes may contribute to hair growth

hair and skin They come in various shapes and sizes throughout the animal kingdom. The coarse body hair of a monkey, for example, is quite different from the soft fur of a cat. The same applies to baldness. While we humans have hair on our heads, because the vast majority of our bodies are hairless, we fall into the “hairless” category. Other mammals with hints of fur like elephants, transparent-haired pigs, and mustachioed walruses fall into the same category.

It’s not all bad to be hairless. Without dense hair, elephants cool off more easily in hot weather and walruses glide effortlessly in water, for example. However, despite the fact that different animals need to go hairless for different survival and evolutionary reasons, the study authors found that hairless mammals accumulated mutations in many of the same genes. More specifically, these genes included those that code for keratin and additional elements that build the hair shaft and promote hair growth.

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The study also indicates that the regulatory regions of the genome are equally important. These areas do not code for the structures that form the hair, but indirectly influence the process. They decide when and where certain genes are activated and how much is created. The researchers discovered other genes for which a role in hair growth had not yet been defined. In summary, this work points to a new set of genes that could play a role in hair growth.

“There are a fair number of genes that we don’t know much about,” adds Dr. Kowalczyk. “We think they might have roles in hair growth and maintenance.”

Genetic study could reveal ways to beat cancer

To arrive at these findings, the researchers searched for genes in hairless animals that evolved at a faster rate compared to their counterparts in furry animals.

“Since the animals are under evolutionary pressure for hair loss, the genes that code for hair become less important,” explains Dr. Clark. “That is why they accelerate the rate of genetic changes that natural selection allows. Some genetic changes can be responsible for hair loss. Others could be collateral damage after the hair stops growing.”

The study authors then developed computational methods capable of comparing hundreds of regions of the genome simultaneously. They examined a total of 19,149 genes and 343,598 conserved regulatory regions across dozens of mammalian species. During that process, the team took special steps to rule out the genetic regions responsible for the evolution of other species-specific traits, such as adaptation to aquatic life.

Dr. Clark says that the fact that an unbiased screen identified known hair genes proves that this approach works. This study also suggests that the genes seen on the screen, considered less well defined, could be just as important for making hair grow as they are for not.

Moving forward, Dr. Clark and his colleagues now use the same approach to analyze and define the genetic regions involved in the Cancer preventionextension of the human life expectancyand understand other health conditions.

He study is published in the magazine eLife.

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