QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Freitas, C. Articles by Palmeirim, I. Search for Related Content PubMed PubMed Citation Articles by Freitas, C. Articles by Palmeirim, I. Social Bookmarking                         What's this?

Evidence for medial/lateral specification and positional information within the presomitic mesoderm

Catarina Freitas^1,*, Sofia Rodrigues^1,*, Jean-Baptiste Charrier², Marie-Aimée Teillet² and Isabel Palmeirim^1,

¹ Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
² Institut d’Embryologie Cellulaire et Moléculaire du Centre National de la Recherche Scientifique et du Collège de France, 49 bis Avenue de la Belle Gabrielle, 94736 Nogent-sur-Marne Cedex, France
^* These two authors contributed equally to this work

Author for correspondence (e-mail: palmeiri{at}igc.gulbenkian.pt)

Accepted September 14, 2001

In the vertebrate embryo, segmentation is built on repetitive structures, named somites, which are formed progressively from the most rostral part of presomitic mesoderm, every 90 minutes in the avian embryo. The discovery of the cyclic expression of several genes, occurring every 90 minutes in each presomitic cell, has shown that there is a molecular clock linked to somitogenesis. We demonstrate that a dynamic expression pattern of the cycling genes is already evident at the level of the prospective presomitic territory. The analysis of this expression pattern, correlated with a quail/chick fate-map, identifies a ‘wave’ of expression travelling along the future medial/lateral presomitic axis. Further analysis also reveals the existence of a medial/lateral asynchrony of expression at the level of presomitic mesoderm. This work suggests that the molecular clock is providing cellular positional information not only along the anterior/posterior but also along the medial/lateral presomitic axis. Finally, by using an in vitro culture system, we show that the information for morphological somite formation and molecular segmentation is segregated within the medial/lateral presomitic axis. Medial presomitic cells are able to form somites and express segmentation markers in the absence of lateral presomitic cells. By contrast, and surprisingly, lateral presomitic cells that are deprived of their medial counterparts are not able to organise themselves into somites and lose the expression of genes known to be important for vertebrate segmentation, such as Delta-1, Notch-1, paraxis, hairy1, hairy2 and lunatic fringe.

Key words: Somite, Segmentation, Molecular clock, Primitive streak, Chick embryo, hairy1, hairy2, lunatic fringe

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				V. Wilson, I. Olivera-Martinez, and K. G. Storey Stem cells, signals and vertebrate body axis extension Development, May 15, 2009; 136(10): 1591 - 1604. [Abstract] [Full Text] [PDF]