This image is a CT scan of a mouse's face — but not just any mouse. Scientists at Berkeley have identified thousands of small DNA regions responsible for influencing the development of facial features — and they used this insight to modify the faces of embryonic mice. The question now is, are humans next?
Top image: Harris Morrison, MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh.
Human faces are incredibly distinctive. But why? New research shows that our unique facial features are forged by more than 4,000 small regions of DNA — but it only takes a few genetic tweaks to subtly alter the shape of our faces.
It’s pretty obvious that facial features are hereditary. Just take a look at family resemblances. The shape of our faces are clearly influenced by our genetics, but scientists have only been able to isolate a small fraction of the genes responsible. Based on the complexity of our features, and those of other animals, it’s clear that there’s plenty more going on at the genetic level.
As Axel Visel of the Lawrence Berkeley National Laboratory in California and his colleagues have recently pointed out, there are thousands of specific non-coding regions of genomes that are working to influence the activity of facial genes. These short stretches of DNA act like switches, turning genes on or off.
These regions are called distant-acting enhancers, or transcriptional enhancers. Some scientists stupidly refer to them as “junk DNA” because they were initially thought to lack function, like encoding proteins. But despite the fact that these transcriptional enhancers are physically located hundreds of kilobases away from their target genes, they appear to regulate the spatial patterns, levels, and timing of gene expression in the normal development of facial features.
To determine this, Visel’s team experimented on genetically modified mice to see if they could alter their facial features during embryonic development.
Okay, to be sure — mice aren’t people, but the same genetic processes apply. As Visel told the BBC, “We're trying to find out how these instructions for building the human face are embedded in human DNA. Somewhere in there there must be that blueprint that defines what our face looks like."
By looking at mouse embryos, Visel could see where — as facial features develop — these switches influence the activation of various face-building genes.
To see if they were on the right track, the researchers removed three of these genetic switches from developing mice. Then, by using a technique called optical projection tomography and CT scans, they studied the resulting facial shapes. By comparing the genetically modified mice with the normal ones, they noticed that some mice developed either long or shorter skulls, while some developed wider or narrower faces. The experiment showed that particular switches can affect the shape of skulls in significant ways.
So does this mean we’ll eventually be able to genetically design human faces at the embryonic stage? Visel himself says it’s unlikely that DNA could be used in the near future to predict someone’s exact appearance, or that parents could predetermine the way their baby looks.
Indeed, these on/off switches merely provide a very blunt brush to affect the development of facial features. It’ll be quite some time before we develop the techniques and insights required to forge a human face in precise ways.
More practically, however, Visel’s research could be used to predict — and even mitigate — certain birth defects, like cleft palates. These types of interventions are quite a ways off, but the new research indicates that it may someday be possible.
Read the entire study at Science: “Fine Tuning of Craniofacial Morphology by Distant-Acting Enhancers.”