spacer gif spacer gif spacer gif spacer gif ARCHIVE ANNOUNCEMENT! spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online 1 August 2007
doi: 10.1242/dev.003665

Development 134, 3155-3165 (2007)
Published by The Company of Biologists 2007
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
dev.003665v1
134/17/3155    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Rifes, P.
Right arrow Articles by Thorsteinsdóttir, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Rifes, P.
Right arrow Articles by Thorsteinsdóttir, S.

Redefining the role of ectoderm in somitogenesis: a player in the formation of the fibronectin matrix of presomitic mesoderm

Pedro Rifes1,2,*, Lara Carvalho1,*,{dagger}, Catarina Lopes1, Raquel P. Andrade3, Gabriela Rodrigues1,2, Isabel Palmeirim3 and Sólveig Thorsteinsdóttir1,2,{ddagger}

1 Departamento de Biologia Animal e Centro de Biologia Ambiental, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
2 Instituto Gulbenkian de Ciência, 2781-901 Oeiras, Portugal.
3 Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, 4710-057 Braga, Portugal.

{ddagger} Author for correspondence (e-mail: solveig{at}fc.ul.pt)

Accepted 2 July 2007

The absence of ectoderm impairs somite formation in cultured presomitic mesoderm (PSM) explants, suggesting that an ectoderm-derived signal is essential for somitogenesis. Here we show in chick that the standard enzymatic treatments used for explant isolation destroy the fibronectin matrix surrounding the anterior PSM, which fails to form somites when cultured for 6 hours. By contrast, explants isolated with collagenase retain their fibronectin matrix and form somites under identical culture conditions. The additional presence of ectoderm enhances somite formation, whereas endoderm has no effect. Furthermore, we show that pancreatin-isolated PSM explants cultured in fibronectin-supplemented medium, form significantly more somites than control explants. Interestingly, ectoderm is the major producer of fibronectin (Fn1) transcripts, whereas all but the anterior-most region of the PSM expresses the fibronectin assembly receptor, integrin {alpha}5 (Itga5). We thus propose that the ectoderm-derived fibronectin is assembled by mesodermal {alpha}5ß1 integrin on the surface of the PSM. Finally, we demonstrate that inhibition of fibronectin fibrillogenesis in explants with ectoderm abrogates somitogenesis. We conclude that a fibronectin matrix is essential for morphological somite formation and that a major, previously unrecognised role of ectoderm in somitogenesis is the synthesis of fibronectin.

Key words: Somitogenesis, Fibronectin, Ectoderm, Presomitic mesoderm, Integrins, Extracellular matrix, Chick






© The Company of Biologists Ltd 2007