Scientists have created a mouse embryo with six legs and no genitals

Genetic bioengineering experts are trying to explain the phenomenon

A team of bioengineers from Portugal has discovered that inactivation of the Tgfbr1 gene in mouse embryos leads to changes in development in the region from the trunk to the tail. The team inactivated the gene responsible for producing the protein, intending to investigate how this change affected the developing spinal cord.

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In their study, published in the journal Nature Communications, the team experimented with Tgfbr1 receptor proteins and were surprised to find that they were able to create a six-legged mouse embryo with no external genitalia.

During embryonic development, the body forms in stages, starting from the head and ending with the tail. At the first transitional stage there is a transition from the head to the body, and at the second — from the body to the tail. This latter transition is associated with a significant reorganization of embryonic structures.

Previous research has shown that in most quadrupeds, control of the hind limbs and external genitalia during development is focused on the same basic processes. For the new study, a team of scientists genetically engineered mice to learn more about this development.

Experts have focused their attention on receptor proteins that develop based on the Tgfbr1 genes. The scientists turned them on and off to see what would happen to the mouse embryo as it developed. In one case, after inactivating the gene and then developing a mouse about halfway through birth, researchers discovered that it had six legs and no external genitalia, and that extra legs were growing where the reproductive system would be. When they repeated the process, they got the same result — six legs in both males and females.

The result came as a surprise to the research team and changed the direction of their work to focus on the reasons for the result. Upon closer examination, they discovered that the Tgfbr1 receptor proteins are directly involved in controlling the development of certain protostructures that become limbs or genitals, and they did this by changing the way DNA folds in the cells that make up those structures.

“Our work reveals remarkable tissue plasticity with potential implications for the evolution of the hindlimb/genital region in tetrapod vertebrates and identifies an additional mechanism of Tgfbr1 activity that may also contribute to the control of other physiological or pathological processes,” the study authors conclude.

< p>The findings open up new opportunities for research into Tgfbr1 signaling pathways and the role they play in the development of other parts of the body. Researchers suspect they may also play a role in the development of the immune system and perhaps in the way cancer cells metastasize.