Environmental Oxygen Exposure Allows for the Evolution of Interdigital Cell Death in Limb Patterning.
Amphibians form fingers without webbing by differential growth between digital and interdigital regions. Amniotes, however, employ interdigital cell death (ICD), an additional mechanism that contributes to a greater variation of limb shapes. Here, we investigate the role of environmental oxygen in the evolution of ICD in tetrapods. While cell death is restricted to the limb margin in amphibians with aquatic tadpoles, Eleutherodactylus coqui, a frog with terrestrial-direct-developing eggs, has cell death in the interdigital region. Chicken requires sufficient oxygen and reactive oxygen species to induce cell death, with the oxygen tension profile itself being distinct between the limbs of chicken and Xenopus laevis frogs. Notably, increasing blood vessel density in X. laevis limbs, as well as incubating tadpoles under high oxygen levels, induces ICD. We propose that the oxygen available to terrestrial eggs was an ecological feature crucial for the evolution of ICD, made possible by conserved autopod-patterning mechanisms.
['Cordeiro|Ingrid Rosenburg|IR|', 'Kabashima|Kaori|K|', 'Ochi|Haruki|H|', 'Munakata|Keijiro|K|', 'Nishimori|Chika|C|', 'Laslo|Mara|M|', 'Hanken|James|J|', 'Tanaka|Mikiko|M|']
D000818:Animals D019521:Body Patterning D019485:Bone Morphogenetic Proteins D016923:Cell Death D002642:Chick Embryo D005121:Extremities D007814:Larva D009024:Morphogenesis D010100:Oxygen D017382:Reactive Oxygen Species D014982:Xenopus laevis
oxygen evolution interdigital cell death reactive oxygen species blood vessels Bmp signaling limb development