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 living marsupial opossumMonodelphis domestica, whose MC transformation during development anatomically mirrors the evolutionary transformation observed in fossils. Specifically, we link increases in cellular apoptosis andTGF-BR2signalling to MC breakdown in opossums. We demonstrate that a simple change inTGF-βsignalling is sufficient to inhibit MC breakdown during opossum development, indicating that changes inTGF-βsignalling 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.
School of Integrative Biology, University of Illinois, 505 S Goodwin Avenue, Urbana, IL 61801, USA.
Daniel J
DJ
Urban
Department of Craniofacial Development and Stem Cell Biology, King's College London, London, UK.
Neal
N
Anthwal
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA.
Zhe-Xi
ZX
Luo
School of Integrative Biology, University of Illinois, 505 S Goodwin Avenue, Urbana, IL 61801, USA.
Jennifer A
JA
Maier
School of Integrative Biology, University of Illinois, 505 S Goodwin Avenue, Urbana, IL 61801, USA.
Alexa
A
Sadier
Department of Craniofacial Development and Stem Cell Biology, King's College London, London, UK.
Abigail S
0000-0001-8871-6094
AS
Tucker
School of Integrative Biology, University of Illinois, 505 S Goodwin Avenue, Urbana, IL 61801, USA ksears2@illinois.edu.|Carl Woese Institute for Genomic Biology, University of Illinois, 1206 W Gregory Drive, Urbana, IL 61801, USA.
Karen E
0000-0001-9744-9602
KE
Sears
D000818:Animals; D005075:Biological Evolution; D004429:Ear Ossicles / Q000033:anatomy & histology*; D004432:Ear, Middle / Q000033:anatomy & histology*; D005580:Fossils; D007568:Jaw / Q000033:anatomy & histology*; D008322:Mammals; D051379:Mice; D048309:Monodelphis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism
D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II
Meckel's cartilage; TGFB signalling; apoptosis; marsupial; origin of mammals