Washington: Scientists have identified thousands of enhancers in the human genome that influence the way facial features develop.
Scientists set out to determine what makes facial morphology so distinct.
Genetics play a major role as evident in the similarities between parents and their children, but researchers have puzzled over what is it in our DNA that fine-tunes the genetics so that siblings - especially identical twins - resemble one another but look different from unrelated individuals.
Researchers at the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) found that gene enhancers - regulatory sequences of DNA that act to turn-on or amplify the expression of a specific gene - are major players in craniofacial development.
"Our results suggest it is likely there are thousands of enhancers in the human genome that are somehow involved in craniofacial development," said Axel Visel, a geneticist with Berkeley Lab's Genomics Division who led the study.
Previous work by Visel and his collaborators, in which they mapped gene enhancers in the heart, the brain and other organ systems demonstrated that gene enhancers can regulate their targets from across distances of hundreds of thousands of base pairs.
To learn whether gene enhancers can also have the same long-distance impact on craniofacial development, Visel and a multinational team of collaborators studied transgenic mice.
Researchers identified more than 4,000 candidate enhancer sequences predicted to be active in fine-tuning the expression of genes involved in craniofacial development, and created genome-wide maps of these enhancers by pin-pointing their location in the mouse genome.
The researchers also characterised in detail the activity of some 200 of these gene enhancers and deleted three of them.
Majority of the enhancer sequences identified and mapped are at least partially conserved between humans and mice, and many are located in human chromosomal regions associated with normal facial morphology or craniofacial birth defects.
"Knowing about the existence of these enhancers, which are inherited from parents to their children just like genes, knowing their exact location in the human genome, and knowing their general activity pattern in craniofacial development should facilitate a better understanding of the connection between genetics and human craniofacial morphology," Visel said.
"Our results also offer an opportunity for human geneticists to look for mutations specifically in enhancers that may play a role in birth defects, which in turn may help to develop better diagnostic and therapeutic approaches," Visel said.
The study was published in the journal Science.
