The scientist and father of the theory of natural selection Charles Darwin was obsessed with domestic pigeons ( Columbia livia ), animals that, after centuries of artificial selection, have an enormous variety of shapes and sizes of beaks. The most striking are those specimens that have such extremely short beaks that they prevent even the parents from feeding their chickens. Until now, modern geneticists have been unable to solve Darwin’s mystery and identify the molecular machinery that controls this trait.
In new work published in the journal Current Biology , a team of biologists at the University of Utah has discovered that a mutation in the ROR2 gene is linked to reduced beak size in numerous domestic pigeon breeds . Surprisingly, ROR2 mutations are also the basis for a human disorder called Robinow syndrome.
“Some of the most striking characteristics of Robinow syndrome are the facial features, which include a broad and prominent forehead and a short and wide nose and mouth, and are reminiscent of the short beak phenotype in pigeons”, explained Elena Boer, author main article. “It makes developmental sense, because we know that the ROR2 signaling pathway plays an important role in vertebrates’ craniofacial development.”
Gene mapping and skulls
The researchers bred pigeons with short and medium beaks in order to assess the traits that the offspring inherited. Furthermore, they did not just measure the beak but also examined the size and shape of the entire skull using micro-CT scanners. In this way, they discovered that there were not only differences in the shape of the beak, but also in the entire shell of the brain. In addition, they compared the genomes: the analysis showed that all individuals with small beaks had the same DNA sequence in an area of the genome that contains the ROR2 gene.
The authors speculate that the short-spike mutation causes the ROR2 protein to fold in a new way, but the team plans to do functional experiments to discover how the mutation affects craniofacial development.
Reference: Boer et al., 2021 A ROR2 coding variant is associated with craniofacial variation in domestic pigeons. Current Biology DOI 10.1016 / j.cub.2021.08.068
Text: University of Utah
