CHICAGO — Why does puberty generally stop children from growing further? A new study may finally provide an answer. Researchers from the University of Illinois-Chicago have identified a potential mechanism that prompts fruit flies to halt their growth. This discovery not only deepens our understanding of animal development but also has implications for comprehending human growth regulation, especially in the context of early-onset puberty.
Throughout the animal kingdom, all creatures begin as single-celled organisms and undergo a phase of growth. However, the precise process by which this growth is halted has remained largely mysterious.
In humans, the signal to cease growth typically occurs during puberty, although it takes several more years for growth to actually stop. The onset of puberty has been occurring at progressively younger ages in recent times, making it crucial to gain a better grasp of the underlying processes that drive this change.
“We know that the onset of puberty is getting younger and younger. But in order to understand why something is changing, you need to understand how it works,” says study author Alexander Shingleton, a professor of biological sciences at the University of Illinois-Chicago, in a university release.
To unravel this complex biological phenomenon, scientists turned to fruit flies, which experience an equivalent of puberty during their metamorphosis from larvae into adults. Many biologists have hypothesized that larvae stop growing when they attain a certain body size, triggering the transformation into adulthood. Similar mechanisms have been observed in other insects, like the kissing bug, which relies on a “stretch receptor” in its abdomen to monitor its size.
Researchers, though, harbored doubts that fruit flies employed the same mechanism. Instead, they postulated that a steroid hormone known as ecdysone, involved in fruit fly growth, played a key role, bearing similarities to human hormones like estrogen and testosterone.
Contrary to prevailing notions, their model indicated that body size itself is not the trigger that induces fruit flies to stop growing. The crucial factor appears to be a “stop growing” switch activated by the gland responsible for producing ecdysone. During the larval stage, this gland receives substantial nutritional information that guides its regulation of ecdysone production. Once ecdysone reaches a certain level, the gland no longer relies on external nutritional cues to make decisions and starts regulating itself.
Researchers propose that this transition from dependence on nutritional information to self-regulation is what ultimately prompts fruit flies to halt their growth.
“It’s not that the fly is measuring itself in a direct way,” notes Shingleton.
The implications of this discovery extend beyond fruit flies, as Shingleton envisions similar studies conducted on mammals could provide further insights into the growth-stopping process in humans. Given the similarities in steroid hormones and the conveyance of nutritional information through insulin in both fruit flies and humans, it is possible that the fruit fly’s growth experience is relevant to our own.
The study is published in the journal Proceedings of the National Academy of Sciences.
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