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Dorsoventral axis determination in the somite: a re-examination
1Department of Anatomy, Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94143, USA.
Development (Cambridge, England)
|April 19, 2000
Summary
Sclerotome cells remain plastic during embryonic development, unlike determined myotome cells. This suggests distinct early and late phases of paraxial mesoderm development, governed by myotome and sclerotome respectively.
Area of Science:
- Developmental Biology
- Embryogenesis
- Somitogenesis
Background:
- Classic dorsoventral somite rotation experiments established timelines for axis determination.
- Gene expression markers are crucial for identifying specific embryonic cell types.
Purpose of the Study:
- To re-examine somite development using gene expression analysis.
- To clarify the developmental plasticity of sclerotome and myotome precursor cells.
Main Methods:
- Repetition of classic somite rotation experiments.
- Analysis of dorsal (myotome) and ventral (sclerotome) gene expression markers.
- Integration of findings with quail-chick transplantation data.
Main Results:
- Histological results align with previous studies.
- Sclerotome cells lose Pax1 mRNA expression, a key sclerotome marker.
- Myotome precursor cells demonstrate rapid determination post-epithelialization.
- Sclerotome tissue fragments show multipotency even late in development.
Conclusions:
- Sclerotome remains phenotypically and morphogenetically plastic during early somitogenesis.
- Myotome precursor cells are determined within hours of somite epithelialization.
- Axis determination occurs early, but the identities of responding tissues (myotome vs. sclerotome) differ from prior assumptions.
- A two-phase model of paraxial mesoderm development is proposed, with early (myotome-governed) and late (sclerotome-governed) determinative phases.