File:Chicken body elongation model.jpg

Chicken Body Elongation Model

Summary of signalling pathway interactions and cell fate changes underlying body axis elongation arrest.

Stage HH22

• Bra is expressed in notochord, CNH, and mesodermal progenitors (overlapping with Sox2 in neural CNH) and is maintained by FGF (and Wnt) signalling
• Sox2 is confined to neural tube and neural-CNH (see Figure 1A).
• Raldh2 and Crabp2 begin to be detected in tailbud mesoderm progenitors (signals that induce Raldh2 here remain to be determined).
• FGF signalling no longer inhibits Raldh2 nor represses Crabp2, and Cyp26a is downregulated; consequently, RA signalling begins to rise in the tailbud.
• FGF signalling is required to maintain Bra (except in proximal notochord) as well as Tbx6L and Wnt3a (not shown) in mesoderm progenitors.

Stage HH24

• FGF signalling suddenly declines, leading to loss of Bra and expansion of Sox2 expression (dashed arrow) into the previous mesoderm progenitor domain, which reflects continued cell ingression from the CNH.
• Crabp2 is now detected in the neural-CNH and position of the mesoderm progenitors, indicating rising retinoid signalling, which can repress FGF ligands and signalling.

Stage HH26/27

• FGF signalling is not detected and the notochord ends abruptly encircled by Sox2 expressing cells.
• Cell death is widespread in the tailbud and is promoted by retinoid signalling.

Links: Chicken Development | Molecular Development | Somitogenesis

Reference

<pubmed>23118616</pubmed>| PLoS Biol.

paper abstract

Copyright

© 2012 Olivera-Martinez 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.

doi:10.1371/journal.pbio.1001415.g009

Figure 9. Journal.pbio.1001415.g009.jpg (Original image resized and relabeled, text modified from figure legend)