File:Chicken antero-posterior endoderm patterning 01.jpg

Model for AP patterning of RA and FGFs in endoderm

At gastrulation and early somitogenesis RA is synthesized in the posterior part of the embryo with its anterior limit around the junction between prospective fore- and hindgut. RA degrading enzyme Cyp26A1 is expressed anteriorly and functions as intracellular sink for RA molecules (upper panel to the left). A RA gradient may be formed in the intermediate region. At the same time FGFs are expressed in the node and in the posterior streak acting in a graded manner along the entire AP axis (upper panel to the right). At stage HH 10 graded activation of RA signaling may be maintained in the dorsal (axial) endoderm anterior to the 6th somite and in the foregut, while LPE is constantly exposured to RA (lower panel). FGFs are produced caudally in the tail bud (lower panel to the left), again acting in a graded manner along the AP axis. Posteriorly, RA may form a contra-gradient to FGFs antagonizing each other as it was shown in pre-somitic mesoderm. Different levels of signaling gradients induce different gene transcription. Whether FGFs also induce genes at the level of the posterior BAs, is not known (lower panel to the right). Color code is explained in the legend beside. Dotted orange lines represent presumptive neural plate. LPE, lateral plate endoderm; LPM, lateral plate mesoderm.

Links: Endoderm | Chicken Development | Molecular Development

Reference

<pubmed>19516907</pubmed>| PLoS One.

Copyright

© 2009 Bayha et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Figure 7. Journal.pone.0005845.g007.jpg doi:10.1371/journal.pone.0005845.g007 Adjusted in size and labelling.