PUBLICATION
Somitogenesis
- Authors
- Gossler, A. and Hrabe de Angelis, M.
- ID
- ZDB-PUB-980420-9
- Date
- 1998
- Source
- Current topics in developmental biology 38: 225-287 (Review)
- Registered Authors
- Gossler, A., Hrabe de Angelis, Martin
- Keywords
- animal; body patterning; cell adhesion; cell communication; cell differentiation; extracellular matrix; mesoderm; mice; morphogenesis; somites
- MeSH Terms
-
- Animals
- Body Patterning
- Cell Adhesion/physiology
- Cell Communication/physiology
- Cell Differentiation/physiology
- Extracellular Matrix/physiology
- Mesoderm/physiology
- Mice
- Morphogenesis
- Somites/physiology*
- PubMed
- 9399080
Citation
Gossler, A. and Hrabe de Angelis, M. (1998) Somitogenesis. Current topics in developmental biology. 38:225-287.
Abstract
We are still far from understanding "somitogenesis" as a whole, but there is an emerging picture of the tissue interactions and molecular mechanisms that
underlie and govern various aspects of this essential multistep patterning process in vertebrates. The ability to form segmental units appears to be a property
specific to the paraxial mesoderm (as opposed to lateral or limb mesoderm), and this ability is probably acquired during early development, when paraxial
mesoderm is specified and emerges from the primitive streak. Signaling molecules expressed in the primitive streak and tail bud are prime candidates
involved in specifying paraxial (as well as other mesodermal) fates. Increasing levels of signaling molecules may be required in posterior regions of the
embryo, and combinatorial signals may be essential to specify the paraxial mesoderm along the entire anterior-posterior axis. However, most of the pivotal
signals, and the ways in which they are integrated and interact, remain enigmatic. Once the paraxial mesoderm is formed, segmentation proceeds largely
without the requirement for continuous interactions with surrounding tissues. Somitomeres represent a morphologic pattern in the mesenchymal presomitic
mesoderm, but their significance for somite formation is unclear. Molecular patterns are established in the presomitic mesoderm and probably are of
functional significance. Cell interactions within the paraxial mesoderm appear to be involved in forming segment borders and ensuring their maintenance
during subsequent differentiation of somites. These interactions are, at least in part, mediated by components of the conserved Notch signaling pathway,
which may have multiple functions during somitogenesis. Epithelial somites are clearly a result of segmentation, but epithelialization is not the mechanism to
form segments, supporting the idea that the basic mechanisms that govern segmentation in the mesoderm of vertebrates are very similar in different species
despite divergent types of resulting segments (i.e., epithelial somites versus rotated myotomes). Concomitantly with segmentation, segment polarity and
positional specification are established. How these processes are linked to, and depend on, each other is unknown, as is how they are regulated and how
segmentation is coordinated on both sides of the neural tube. In contrast to early patterning in the presomitic mesoderm, patterning of the mature somites
during their subsequent differentiation is the result of extensive tissue interactions. Virtually all tissues in close proximity to somites provide signals that are
involved in induction or inhibition of particular differentiation pathways, but how these pathways are initiated is less clear. Some of the molecules mediating
inductive signals and tissue interactions are known, and a growing number of candidate genes are potentially involved in regulating various steps of
somitogenesis. The roles of these genes have yet to be analyzed. In addition, the molecular genetic analysis of mutations affecting somitogenesis, which
were collected in the mouse and more recently in the zebrafish (Driever et al., 1996; Haffter et al., 1996; van Eeden et al., 1996), promises to add
important new insights into this process. Much remains to be done, but the tools are at hand to provide further understanding of the molecular mechanisms
underlying somitogenesis.
Genes / Markers
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Orthology
Engineered Foreign Genes
Mapping