Scientists led by an Indian-origin researcher have for the first time grown dinosaur-like snouts on ordinary chicken embryos in a lab.
Researchers successfully replicated the molecular processes that led from dinosaur snouts to the first bird beaks.
Using the fossil record as a guide, a research team replicated ancestral molecular development to transform chicken embryos in a laboratory into specimens with a snout and palate configuration similar to that of small dinosaurs such as Velociraptor and Archaeopteryx.
"Our goal here was to understand the molecular underpinnings of an important evolutionary transition, not to create a 'dino-chicken' simply for the sake of it," said Yale University paleontologist and developmental biologist Bhart-Anjan S Bhullar, lead author of the study published in the journal Evolution.
Bhullar and his colleagues developed a novel approach to finding the molecular mechanism involved in creating the skeleton of the beak.
First, they did a quantitative analysis of the anatomy of related fossils and extant animals to generate a hypothesis about the transition; next, they searched for possible shifts in gene expression that correlated with the transition.
The team looked at gene expression in the embryos of emus, alligators, lizards, and turtles.
Researchers discovered that both major living lineages of birds (the common neognaths and the rarer paleognaths) differ from the major lineages of non-bird reptiles (crocodiles, turtles, and lizards) and from mammals in having a unique, median gene expression zone of two different facial development genes early in embryonic development.
This median gene expression had previously only been observed in chickens.
Using small-molecule inhibitors to eliminate the activity of the proteins produced by the bird-specific, median signalling zone in chicken embryos, the researchers were able to induce the ancestral molecular activity and the ancestral anatomy.
Not only did the beak structure revert, but the process also caused the palatine bone on the roof of the mouth to go back to its ancestral state.
"This was unexpected and demonstrates the way in which a single, simple developmental mechanism can have wide-ranging and unexpected effects," said Bhullar, who co-led the study with Harvard University developmental biologist Arhat Abzhanov.
