The age at which girls reach puberty is influenced by a set of genes that were previously only known to be involved in the development of a fetus before birth, according to a new study.
The timing of puberty varies widely among people. Scientists are interested in understanding the factors that influence when people enter puberty, because this timing has been linked with the risk of developing health conditions — such as obesity, diabetes, heart disease and breast cancer — later in life.
Many factors — some genetic, and others nongenetic — have a role in the timing of puberty. To find the genes that influence puberty in girls, researchers analyzed the genomes of more than 180,000 women of European descent, and found more than 100 genetic variations that were associated with the age at which girls experienced their first menstrual period.
Six of these genetic differences were found within a set of genes known as "imprinted" genes, according to the study, published today (July 23) in the journal Nature. [ Unraveling the Human Genome: 6 Molecular Milestones ]
Imprinted genes are unusual in that only one of the two copies that people inherit from their parents is active, and the other is silenced. (For most of the genes, the copies inherited from the mother and father are equally active.)
This finding means that the timing of puberty may depend, in part, on which copy is active, the researchers said. In other words, one parent will end up having a stronger influence than the other.
"Up until now, imprinted genes were largely thought to be important for growth and development of babies before birth," John Perry, a researcher at the University of Cambridge in the United Kingdom and one of the researchers involved in the study, said in an interview with Nature. "However, our study supports the idea that these genes continue to play a role in later-life health and disease."
One idea that is popular among scientists is that imprinted genes demonstrate the competition between maternal and paternal genes in furthering their own genetic interests, Perry said.
The new findings also suggest that hundreds, or perhaps thousands, of genes work in a complex network to determine the timing of puberty, the researchers said.
Many of the genetic differences found in the new study were shown in previous studies to have other links with puberty, while others have been implicated in body weight and various diseases, including rare disorders associated with puberty. More research is needed to understand exactly how all of these genes work to determine puberty's timing, the researchers said.
"We were amazed at the diverse range of biological pathways and processes that all genes fell into," such as energy, autoimmunity and sex hormones, Perry said.