A new developmental mechanism for the separation of the mammalian middle ear ossicles from the jaw

Multiple mammalian lineages independently evolved a definitive mammalian middle ear (DMME) through breakdown of Meckel's cartilage (MC). However, the cellular and molecular drivers of this evolutionary transition remain unknown for most mammal groups. Here, we identify such drivers in the livin...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2017-02, Vol.284 (1848), p.20162416-20162416
Main Authors: Urban, Daniel J., Anthwal, Neal, Luo, Zhe-Xi, Maier, Jennifer A., Sadier, Alexa, Tucker, Abigail S., Sears, Karen E.
Format: Article
Language:English
Subjects:
Animals
Apoptosis
Biological Evolution
Breakdown
Cartilage
Ear Ossicles - anatomy & histology
Ear, Middle - anatomy & histology
Evolution
Fossils
Jaw
Jaw - anatomy & histology
Mammals
Marsupial
Marsupials
Meckel's Cartilage
Mice
Middle ear
Monodelphis
Monodelphis domestica
Origin Of Mammals
Placenta
Protein-Serine-Threonine Kinases - metabolism
Receptor, Transforming Growth Factor-beta Type II
Receptors, Transforming Growth Factor beta - metabolism
Signaling
Tgfb Signalling
Transforming Growth Factor beta - metabolism
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Summary:Multiple mammalian lineages independently evolved a definitive mammalian middle ear (DMME) through breakdown of Meckel's cartilage (MC). However, the cellular and molecular drivers of this evolutionary transition remain unknown for most mammal groups. Here, we identify such drivers in the living marsupial opossum Monodelphis domestica, whose MC transformation during development anatomically mirrors the evolutionary transformation observed in fossils. Specifically, we link increases in cellular apoptosis and TGF-BR2 signalling to MC breakdown in opossums. We demonstrate that a simple change in TGF-β signalling is sufficient to inhibit MC breakdown during opossum development, indicating that changes in TGF-β signalling might be key during mammalian evolution. Furthermore, the apoptosis that we observe during opossum MC breakdown does not seemingly occur in mouse, consistent with homoplastic DMME evolution in the marsupial and placental lineages.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2016.2416