For quite a long time, researchers have been trying to figure out the origin of the extremely lengthy trunks that make up a snake’s body. This mystery of animal development would be able to shed light on the mechanisms controlling the tissues that form that trunk, including the spinal cord and skeleton. A team of researchers led by Moisés Mallo from the Instituto Gulbenkian de Ciência (IGC, Portugal) have uncovered the key factor that regulates the development of the trunk among vertebrates and also explains why snakes have such a unique body. The new data was published within the newest edition of Developmental Cell Journal and was highlighted on the cover. The findings may open new avenues to the study of spinal cords and how they regenerate.
What makes snakes so unique is that they are not like other animals that may vary in size and shape but all have bodies with a head and a neck, a trunk and a tail. The relative size of each of these body sections is what makes a large part of the body differences among these animals. All vertebrates develop by consecutive phases, all forming each region of the body in a certain order, working from head all the way down to the tail. This development is caused by genetic instructions that inform the beginning and the end of each body region’s formation. Moisés Mallo’s laboratory has been working on cracking genetic codes that work to control the development of trunks and tails in vertebrates. In order to reach this goal they had to study mice that had extremely large or small trunks. Mallo says the team thought that the analysis of these could provide them with the key that would unveil the code of trunk formation.
Their experiments led to the realization that the key controller of trunk development was the OCT4 gene, a gene that is essential in the regulation of stem cells. Many other vertebrates also have OCT4, meaning this gene could play very similar roles in other animals and may be responsible for the lengthy trunks of snakes. First author of this study, Rita Aires says that they have found the OCT4 gene is like a switch that leads to trunk formation, but they are still not able to explain the different trunk length observed in vertebrates, especially in snakes. They tested if this switch was being turned on and off during different periods of embryonic development in snakes compared to mice.
Researchers realized that the OCT4 gene was kept active during a longer period of time in snakes in comparison to other animals. They also were able to show that this led to changes in the snake genome that happened during reptile evolution, which placed the OCT4 gene next to a region of DNA that keeps this gene in an “on” state during extended periods of embryonic development.
Rita Aires says the formation of different body regions works as a strong-arm contest of genes. Genes involved in trunk formation need to start ceasing activity so that the genes involved in tail formation can start working. In the case of snakes, they observed that the OCT4 gene is kept active during a longer period of embryonic development, which explains why snakes have such a long trunk and a very short tail.
Moisés Mallo explains further, saying that the team identified a key factor that allows essentially unlimited growth of trunk structures, as long as it remains active. Now the team will investigate if they can use the OCT4 gene and the DNA region that maintains its activity to expand the cells that make the spinal cord, trying to regenerate it in the event of injury.