In amniotes such as birds and mammals, the cells between the fingers are removed by cell death to form the limbs.Until now, it has not been clarified why this mechanism of "interfinger cell death", which does not occur in amphibians such as frogs and newts, appeared in amniotes.

　The research group noted that many amphibians are aquatic during the larval stage.During the time when the limbs are formed, amphibians breathe using oxygen that is slightly dissolved in the water.On the other hand, in the case of embryos that develop in eggs such as chickens and embryos of mammals such as mice and humans, oxygen in the atmosphere can be efficiently taken in through the blood vessels and placenta in the eggs. ..

　Therefore, we analyzed the rare frog, Kokikoyasugaeru, which lived in the larvae.Interestingly, in the larvae of the Kokikoyasu frog, which breathes with oxygen from the atmosphere, cells causing cell death were found between the toes.

　From here, the research group started an experiment to elucidate the relationship between oxygen and interdigital cell death, and when breeding Xenopus laevis larvae with webbing on their feet in a high-concentration oxygen environment, cell death that should not occur originally Found to happen.It was also found that cell death also occurs in larvae with increased blood vessels (ie, sources of oxygen) between the fingers.Furthermore, it was found that the process of interfinger cell death requires the production of reactive oxygen species between the fingers.

　This result is that, in the process of evolution, environmental changes (that is, exposure to high concentrations of oxygen) associated with the advancement of living organisms to land have created a new mechanism called "interfinger cell death". It can be said that it suggested.

Paper information:[Developmental Cell] Environmental oxygen exposure allows for the evolution of interdigital cell death in limb patterning