The face of a bird is much different from the face of a mammal. While birds tend to have beaks — some long and sharp, others wide and flat — mammals tend to have snouts and noses. Yet, while they differ greatly (except perhaps the platypus), new research has revealed that, when it comes to constructing their faces, birds and mammals use the same pathways and gene networks.
The new study, published in Science Advances, takes a closer look at an animal's embryonic development and the signals that occur throughout it to control the face’s shape. Through this, the researchers led by Markéta Kaucká at the Max Planck Institute for Evolutionary Biology, in collaboration with Axel Visel and Laura Cook from the Lawrence Berkeley National Laboratory in California, determined how these shared pathways and networks can create different faces.
It turns out that timing and location may play a major part in it.
Gene Expression During Embryonic Development
Facial diversity, according to the study, reflects adaptations that help species thrive in specific ecological niches and support distinct feeding strategies. The facial structure begins to develop during the embryonic stage, thanks to signaling hubs known as “developmental organizers.”
From here, signals are released, instructing nearby cells to develop into facial features. In the face, according to a press release, one of the developmental organizers can be found in the ectoderm and can instruct the release of molecules known as morphogens. What the research team found interesting is that many of the morphogens across birds and mammals were the same. If this is the case, then how do the genes know to create distinct faces?
The answer is not so complex. The team found that facial diversity likely arises from changes in non-coding DNA sequences. This change can act like a switch, controlling when a gene is expressed.
“During embryonic development, many genes are used repeatedly in different tissues and at multiple stages,” Kaucká said in a press release. “If you change the gene itself, you risk breaking many processes and body parts at once. But by modifying the regulatory elements that control where and when the gene is used, evolution can reshape specific features, such as the face, without compromising the whole organism.”
Read More: Over 20 Years, One Mouse Was Cloned for 58 Generations — Until the Line Collapsed
Comparing a Mouse and a Chicken
For their research, the team compared the development of mouse and chicken faces. During embryonic development, the team noted an unexpected evolutionary change. The main differences between chicken and mouse gene regulation were more pronounced in the mesenchymal cells — cells that can develop into various tissues, from muscle to bone — than in the developmental organizers. These cells usually receive instructions from the developmental organizers about where to move and what to become.
“These cells eventually give rise, for instance, to cartilage and bone, acting as the primary builders of the facial skeleton, and dictating the facial shape. Our results suggest that facial diversity is not only shaped by changes in how signals are produced, but also by how they are perceived by other cells,” Stella Kyomen, a Ph.D. student and the first author of the study, said in a press release.
A Connection to Human Face Shape
During the study, the research team was also curious whether the gene signaling that controls face shape in mice and chickens played a role in variation in human faces.
By comparing their collected data with large human genetic studies focused on differences in facial shape, they found that many of the active elements in facial development overlapped with genomic regions commonly associated with the human face.
“This suggests that the same regulatory mechanisms that evolution uses to generate diversity between species also contribute to variation within our own species,” Kyomen said.
“These are fascinating data because they show that genes provide the blueprint, but it is the regulatory landscape that determines how that information is used. By integrating species-specific epigenomic data, we can now identify the broader conserved mechanisms that shape facial diversity across vertebrates,” Axel Visel, a research collaborator, added in the press release.
According to the team, more research is needed, and they hope to use this data to gain a better understanding of facial development.
“The generation of single-cell epigenomic data, especially from chicken facial tissues, will be an important resource for investigating craniofacial evolution,” Laura Cook, a study collaborator, said in the press release.
Read More: Ancient Fish Fins May Have Given Rise to Human Hands
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article includes information from a study published in Science Advances: Cis-regulatory evolution shapes facial diversity in birds and mammals
