• Contributed by Mary Metkus

The science behind sex-crazed teenagers

Puberty: the bane of parents’ lives. Just when they think they have this whole parenting business down, adolescence rears its ugly head. Hormones rule the world of puberty, changing a person from an innocent little child into a full-grown teen making their way through the perils of adulthood. While they get a bad reputation for their adverse effects on emotions, hormones help humans and animals alike mature.

It is known that hormones are necessary to produce key changes in physical development during puberty. Yet, the question of how behavior matures is not well understood. We all know that rambunctious teenager does not act the same as the innocent child he or she was before puberty hit, but why is this the case?

Dr. Julide Bilen set out to study this biological problem using the sexual maturation of female fruit flies. She showed that a particular hormone called Juvenile Hormone is a key component of behavioral maturation in female fruit flies. Thus, elucidating a key component of behavioral maturation.

In fruit flies, young females are unreceptive to male courtship attempts to mate. However, at about two days old, the females become receptive and will mate with the eager males. This behavioral switch from unreceptive to receptive is required for mating success, but what is controlling the maturation of this behavior is unknown.

Now enter Juvenile Hormone (JH). JH is a hormone in fruit flies that is known to be necessary for reproductive maturation. At about two days old, the amount of JH in the fly increases. It is involved in maturation of the ovaries, and the production of important chemicals to attract males. This obvious role in physical maturation is what lead Bilen to test its role in behavioral maturation.

Bilen showed that when JH is removed completely, the females are delayed in becoming receptive to courting males. To do this, the region of the fly brain which releases JH was removed in developing flies. The females lacking this brain region were significantly delayed in receptivity, thus showing the JH is necessary for the maturation of sexual behavior in the female fly.

To determine exactly how JH is working to regulate the onset of female mating, the role of the receptors for JH were examined. JH is known to act through two receptors in the fly body to regulate physical maturation: Met and gce. To test if it acts the same way to regulate behavior in the nervous system, two fly populations were engineered each with a non-functional form of one of the receptors.

After surveying their receptivity, it was shown that only one of the two receptors, the Met receptor, is being used by JH to regulate the onset of female mating. Flies with completely non-functional Met receptors displayed the same delayed maturation as flies not producing any JH in the previous experiment. This shows that even though the hormone was being produced, it could not act to activate the behavioral switch for receptivity.

From these significant results, Bilen concluded that sexual maturation of behavior in female fruit flies is due in part to Juvenile Hormone. She also discovered that Juvenile Hormone is acting specifically through the Met receptor.

Previous to this study, not much was known about how precise timing of behavioral maturation could be controlled in the transition from childhood to adulthood. These changes in behavior are crucial for sexual reproduction, both in humans and animals. It is far easier to study the maturation of physical aspects than behavior, which requires coordination of neurons in the brain. Bilen provides an important piece of the puzzle in how something as complex as behavior could be regulated as an animal matures.

However, there are still questions to be answered. Is Juvenile Hormone acting directly in neurons to control the timing of maturation or is it acting indirectly in another part of the body? If it is in the nervous system, how is it controlling the maturation of the neurons themselves to produce changes in behavior? To test these questions, flies should be made with non-functional Met receptors only in the nervous system to see if maturation is still delayed in female flies.

If you’ve ever seen a teenager go through puberty, you know maturation is not a simple process. However, this research helps us understand exactly how one’s behavior could be changed and matured through hormones. Yet, there is still a bit to go before parents will know why their pubescent children won’t clean their rooms.