Puberty: Genetic "On-Switch" Sheds Light on Why Teens Suddenly Get Horny

Puberty is best known for a massive surge in sex-related hormones that begins the process of growing up. But as well-acquainted as we are with this sudden life-altering change, nobody is entirely sure what sets the whole process in motion. A paper released this week in eLife, however, proposes an explanation: an on-switch in the brain that tells the body it’s time to become an adult.

Laura Pereira, Ph.D., a postdoctoral researcher at Columbia University and co-author on the new paper, has been working with biologist Oliver Hobert, Ph.D., to show that a handful of genes act like a genetic on-switch for puberty in the brain, specifically in males.

"I think it’s very obvious from this work and other work how little we know about puberty that has become an evident issue.

She tells Inverse that puberty is as perplexing to researchers as it is to confused teens. “I think it’s very obvious from this work and other work how little we know about puberty that has become an evident issue,” she says. The team’s work on the transparent worm Caenorhabditis elegans, however, brings us one step closer to understanding what kicks off the surge of hormones that makes puberty so momentous.

Activating certain genes in male C. elegans, they found, prompted specific patterns of male development in the brain and also shifted their behavior to be geared decidedly more toward sex. The team thinks that those genes might constitute the “on-switch” responsible for the sudden surge in hormones.

“I would say that our study points to the potential existence of genetic pathways upstream of hormone release in the brain,” Hobert, a professor in Columbia’s department of biochemistry and molecular biophysics, tells Inverse. “The hormonal control of puberty is very well understood and studied, but mechanisms that set such hormonal control aspects in motion, are much less well understood.”

Pereira found that young worms express a gene called Lin-41. But when they reach a certain age, that gene is repressed and some neurons begin expressing a different gene called Lin-29A. That’s when things start changing. Pereira noticed that the brains of the male worms that had started expressing Lin-29A began to develop differently: Their neurons took on a slightly different shape than those seen in younger worms, which she calls a “remodeling of the male nervous system.” Even more importantly, also changed how they behaved.

"Mainly what we know is that when you become an adult, and I’m talking as generally as I can for every animal species, you must reproduce.

Once their neurons started expressing this new gene, male worms started seeking out mates — which they didn’t do during the juvenile stage. Pereira also noticed that worms who didn’t carry that gene didn’t display these same behaviors.

“Mainly what we know is that when you become an adult, and I’m talking as generally as I can for every animal species, you must reproduce,” she says. “Juveniles don’t mate, so the brain is remodeling to be able to control behaviors that are adult-specific, such as courting or mating and parenting,” she continues.

What’s even more interesting is that Lin-29A is only expressed in the brains of male worms, which supports the idea that male and female brains take slightly different paths towards adulthood. Importantly, Pereira still isn’t sure whether there’s a Lin29A counterpart in the female brain. She calls that an “open question.”

Aside from helping us understand what jump-starts the awkward, uncomfortable, and thrilling final stage of childhood, better characterizing these minute differences in juvenile worm development could eventually be helpful in understanding how to treat certain diseases in humans.

“During puberty many diseases arise,” says Pereira, “so it’s particularly interesting to understand how the brain is undergoing these changes and how the changes are also different between the different sexes.”