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Wiley Interdiscip Rev Dev Biol 2017 Sep 01;65:. doi: 10.1002/wdev.275.
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Mouth development.

Chen J , Jacox LA , Saldanha F , Sive H .

A mouth is present in all animals, and comprises an opening from the outside into the oral cavity and the beginnings of the digestive tract to allow eating. This review focuses on the earliest steps in mouth formation. In the first half, we conclude that the mouth arose once during evolution. In all animals, the mouth forms from ectoderm and endoderm. A direct association of oral ectoderm and digestive endoderm is present even in triploblastic animals, and in chordates, this region is known as the extreme anterior domain (EAD). Further support for a single origin of the mouth is a conserved set of genes that form a 'mouth gene program' including foxA and otx2. In the second half of this review, we discuss steps involved in vertebrate mouth formation, using the frog Xenopus as a model. The vertebrate mouth derives from oral ectoderm from the anterior neural ridge, pharyngeal endoderm and cranial neural crest (NC). Vertebrates form a mouth by breaking through the body covering in a precise sequence including specification of EAD ectoderm and endoderm as well as NC, formation of a 'pre-mouth array,' basement membrane dissolution, stomodeum formation, and buccopharyngeal membrane perforation. In Xenopus, the EAD is also a craniofacial organizer that guides NC, while reciprocally, the NC signals to the EAD to elicit its morphogenesis into a pre-mouth array. Human mouth anomalies are prevalent and are affected by genetic and environmental factors, with understanding guided in part by use of animal models. WIREs Dev Biol 2017, 6:e275. doi: 10.1002/wdev.275 For further resources related to this article, please visit the WIREs website.

PubMed ID: 28514120
PMC ID: PMC5574021
Article link: Wiley Interdiscip Rev Dev Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: aldh1a2 cpn1 fgf8 frzb hesx1 otx2 pitx2 pitx3 prdm1 shh tbxt
GO keywords: gut morphogenesis [+]

Disease Ontology terms: Nager acrofacial dysostosis

Article Images: [+] show captions
References [+] :
Adhikari, A genome-wide association scan implicates DCHS2, RUNX2, GLI3, PAX1 and EDAR in human facial variation. 2016, Pubmed