Danish researcher discovers ‘missing link’ in the fruit fly
Why do children enter puberty earlier and earlier? Assistant professor in medical biology at Roskilde University, Kim Rewitz, might have discovered the key to the explanation in the fruit fly.
How the human body knows when to begin the transition from child to adult has long been one of science’s great mysteries.
Now, a researcher from Roskilde University in Denmark has discovered an important link in relation to what initiates sexual maturity in fruit flies. The ground-breaking discovery might help us to understand the mechanism behind human puberty, and at the same time enlighten us as to why young people in the Western world enter puberty earlier and earlier.
Searching for answers for a century
The fruit fly is one of the most commonly used organisms when it comes to research within genetics and biomedicine, partly because of its short reproduction time and the fact that it is cheap to breed and partly because it is genetically simple and its DNA has been mapped. This gives researchers a big ‘tool box’ to help them answer biological questions.
A century ago, researchers discovered that there was a factor in the fruit fly’s brain that could initiate sexual maturity. It was not possible to identify this factor, but it was certain that there was something in the brain that could trigger the process.
Kim Rewitz, assistant professor in medical biology, Department of Science, Systems and Models (NSM), said:
“Twenty years ago it was discovered what this factor was and that the molecule was a peptide hormone similar to a number of growth factors being produced and released from some nerve cells. It was also discovered that the peptide hormone affects the gland that produces steroid hormone, and they realised that, due to the structure of the molecule, this signal molecule from the brain had to be something that bound to the gland’s surface.”
“However, it was not possible to find the receptor of the signal on the cell's surface. We’ve been looking for it for 20 years, and now we've found it. It was a huge missing link in understanding the system involving sexual maturity", said Kim Rewitz.
The cells’ receptors can be divided into different groups. The problem was that researchers had been looking at the wrong group of receptors. Kim Rewitz got the idea of looking at a different group of receptors after a stay onboard the Danish Galathea Expedition where he talked to some researchers from the University of Southern Denmark (SDU), who are experts in analysing proteins by using so-called proteome analyses that analyse the human body’s proteins. The idea came from the subsequent proteome analyses showing that the way the hormone communicates with cells is the same used by growth factors in humans. Consequently, the hormone had to use a different group of receptors than previously anticipated.
“After I discovered the receptor, I spent eighteen months in the United States with two other researches, Michael O’Connor and Naoki Yamanaka, characterising it, and fortunately we had our results published before anyone else. It’s always a bit nerve-racking when you feel you've discovered something pretty big because you know that around the world, there's a lot of researchers trying to discover exactly the same", said Kim Rewitz.
Early puberty
The results mean that, for the first time, we have an actual set of tools providing us with the opportunity to understand what initiates sexual maturity. Fruit flies’ system is in many ways very similar to the system initiating puberty in humans and can therefore be used as a model. Hopefully, over time, it can help us better understand human puberty, which is still a mystery to researchers around the world.
A survey from the Department of Growth and Reproduction (Vækst og Reproduktion) at Rigshospitalet, Denmark shows that in Denmark puberty occurs a whole year earlier than it did just fifteen years ago. In fact, most girls develop breasts already before their tenth birthday. In recent years, the Copenhagen Royal Chapel Coir also has had problems with early puberty and voices breaking.
When puberty sets in too soon, it affects the body in many different ways. However, researchers are not completely sure on how, but they fear that the hormonal stimulation increases the risk of breast cancer later in life. Also, children with early puberty will often stop growing early and thus not be as tall as they would otherwise be.
One of the theories is that chemicals can alter the biological clock telling the body that now it is time to initiate puberty. Another theory is that obesity might be the cause of early puberty. However, researchers have not come so far that they can prove this. Nevertheless, it is an important step that we are now a bit closer to understanding what happens when fruit flies enter “puberty”. The theory is that it is a similar process that takes place in humans.
“I hope that the results can help us understand the whole complicated system involving puberty and make us able to transfer some of these things to humans in the long term. Everything indicates that a high calorie diet can contribute to accelerating puberty. This applies to both fruit flies and humans, but we need much more knowledge about the processes taking place in the human body", said the Danish researcher.