title: Dynamic control of head mesoderm patterning.
abstract: The embryonic head mesoderm gives rise to cranial muscle and contributes to the skull and heart. Prior to differentiation, the tissue is regionalised by the means of molecular markers. We show that this pattern is established in three discrete phases, all depending on extrinsic cues. Assaying for direct and first-wave indirect responses, we found that the process is controlled by dynamic combinatorial as well as antagonistic action of retinoic acid (RA), Bmp and Fgf signalling. In phase 1, the initial anteroposterior (a-p) subdivision of the head mesoderm is laid down in response to falling RA levels and activation of Fgf signalling. In phase 2, Bmp and Fgf signalling reinforce the a-p boundary and refine anterior marker gene expression. In phase 3, spreading Fgf signalling drives the a-p expansion of MyoR and Tbx1 expression along the pharynx, with RA limiting the expansion of MyoR. This establishes the mature head mesoderm pattern with markers distinguishing between the prospective extra-ocular and jaw skeletal muscles, the branchiomeric muscles and the cells for the outflow tract of the heart.
authors.affiliation: School of Biomedical and Health Sciences, King's College London, London SE1 1UL, UK.
authors.forename: Ingo
authors.initials: I
authors.lastname: Bothe
authors.forename: Gennadiy
authors.initials: G
authors.lastname: Tenin
authors.forename: Adelola
authors.initials: A
authors.lastname: Oseni
authors.forename: Susanne
authors.initials: S
authors.lastname: Dietrich
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D002642:Chick Embryo; D002645:Chickens; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D006257:Head / Q000196:embryology*; D017403:In Situ Hybridization; D008648:Mesoderm / Q000196:embryology* / Q000378:metabolism*