Institute of Molecular Genetics of the Czech Academy of Sciences
Some essential structures important for head development in vertebrates had already evolved in the common ancestor of all chordates. This surprising finding was demonstrated by scientists from the Institute of Molecular Genetics of the Czech Academy of Sciences while studying the amphioxus, which belongs to chordates. The amphioxus itself has only the so-called head end.
The cephalopods are small, elongated, fish-like marine animals, closely related to vertebrates. They are of great interest to evolutionary biology because they provide insight into the early evolution of chordates – animals with an axial support system, which includes all vertebrates, including humans. In addition, amphioxus has retained many features that probably existed in a common chordate ancestor.
That is why the team from the Institute of Molecular Genetics of the Czech Academy of Sciences focused on it. The results of the study provide important evidence that essential features of vertebrate head development are derived from a common ancestor of all chordates.
“We were interested in structures associated with the vertebrate head, such as the neural crest and the prechordal plate. For a long time, it was assumed that both structures were innovations of vertebrates and that amphioxus, a representative of the basic line of chordates, does not have them,” explains Iryna Kozmikova, team leader from the Institute of Molecular Genetics.
The neural crest is a set of cells that run along the dorsal side of the developing embryo and are involved in the development of many important structures such as the bones and cartilage of the head, the face, nerves, and pigment cells. The prechordal plate is a basic cellular structure located at the front of the embryo that plays a key role in the formation of the skull and brain.
“In humans, failure of the development of the prechordal plate can lead to severe developmental disorders, such as incomplete separation of the cerebral hemispheres, which can cause severe brain and developmental disorders. Defects of the neural crest can cause disorders in the development of the head and facial structures, such as cleft lip and palate or deformation of the skull and face,” explains Iryna Kozmikova.
The amphioxus reveals the evolutionary origins of the vertebrate head
The research, which included analysis of cell populations, manipulation of signaling pathways, and transgenic experiments, showed that the amphioxus goes through similar developmental stages as vertebrates. Using advanced methods, the scientific team analyzed amphioxus embryonic cells at four developmental stages. Scientists have identified cells similar to the prechordal plate and the neural crest.
“By combining these methods, we identified specific cell populations that share genetic features with cells involved in head development in vertebrates, which suggests that the main features of head development may have arisen in a common ancestor of vertebrates and the amphioxus,” summarizes Iryna Kozmikova.
Understanding the history as well as hope for the future
This research supports the theory that some of the major structures associated with head development in vertebrates evolved already in the common ancestor of all chordates. A better understanding of these evolutionary mechanisms can not only provide insight into the history of life on Earth, but also aid in research into developmental disorders associated with the formation of the human head and facial structures.
Anna Markos, Jan Kubovciak, Simona Mikula Mrstakova, Anna Zitova, Jan Paces, Simona Machacova, Zbynek Kozmik-Jr, Zbynek Kozmik and Iryna Kozmikova: Cell type and regulatory analysis in amphioxus illuminates evolutionary origin of the vertebrate head. Nat Commun 2024. [doi]
Author of the introductory photo of amphioxus: Iva Dobiášovská.