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Dev Biol 2014 Jun 15;3902:231-46. doi: 10.1016/j.ydbio.2014.03.003.
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Evolutionarily conserved morphogenetic movements at the vertebrate head-trunk interface coordinate the transport and assembly of hypopharyngeal structures.

Lours-Calet C , Alvares LE , El-Hanfy AS , Gandesha S , Walters EH , Sobreira DR , Wotton KR , Jorge EC , Lawson JA , Kelsey Lewis A , Tada M , Sharpe C , Kardon G , Dietrich S .

The vertebrate head-trunk interface (occipital region) has been heavily remodelled during evolution, and its development is still poorly understood. In extant jawed vertebrates, this region provides muscle precursors for the throat and tongue (hypopharyngeal/hypobranchial/hypoglossal muscle precursors, HMP) that take a stereotype path rostrally along the pharynx and are thought to reach their target sites via active migration. Yet, this projection pattern emerged in jawless vertebrates before the evolution of migratory muscle precursors. This suggests that a so far elusive, more basic transport mechanism must have existed and may still be traceable today. Here we show for the first time that all occipital tissues participate in well-conserved cell movements. These cell movements are spearheaded by the occipital lateral mesoderm and ectoderm that split into two streams. The rostrally directed stream projects along the floor of the pharynx and reaches as far rostrally as the floor of the mandibular arch and outflow tract of the heart. Notably, this stream leads and engulfs the later emerging HMP, neural crest cells and hypoglossal nerve. When we (i) attempted to redirect hypobranchial/hypoglossal muscle precursors towards various attractants, (ii) placed non-migratory muscle precursors into the occipital environment or (iii) molecularly or (iv) genetically rendered muscle precursors non-migratory, they still followed the trajectory set by the occipital lateral mesoderm and ectoderm. Thus, we have discovered evolutionarily conserved morphogenetic movements, driven by the occipital lateral mesoderm and ectoderm, that ensure cell transport and organ assembly at the head-trunk interface.

PubMed ID: 24662046
PMC ID: PMC4010675
Article link: Dev Biol
Grant support: [+]

Species referenced: Xenopus
Genes referenced: actl6a alx4 dlx2 fgf8 lbx1 pax3 pc.1 prrx1 sox10 tcf15 wnt6

Article Images: [+] show captions
References [+] :
Ainsworth, Developmental stages of the Japanese quail. 2010, Pubmed