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Mesodermal subdivision along the mediolateral axis in chicken controlled by different concentrations of BMP-4
A Tonegawa1, N Funayama, N Ueno
1Department of Bioscience, Kitasato University, Sagamihara, Japan.
Abstract:
Molecular mechanisms by which the mesoderm is subdivided along the mediolateral axis in early chicken embryos have been studied. When the presomitic mesoderm (medial mesoderm) was transplanted into the lateral plate, the graft was transformed into lateral plate tissue, indicating that the primitive somite was not fully committed and that the lateral plate has a cue for mesodermal lateralization. Since the lateral plate expresses a high level of BMP-4 mRNA, a member of the TGF-beta family, we hypothesized that it is the molecule responsible for the lateralization of the somite. To test this, we transplanted COS cells producing BMP-4 into the presomitic region. Those cells locally prevented the presomitic cells from differentiating into somites, converting them instead into lateral plate mesoderm, which was revealed by expression of cytokeratin mRNA, a marker for the lateral plate. The effect was dependent on the level of effective BMP-4: with a high level of BMP-4, the somite was transformed completely to lateral plate; with a low level, the somite formed but was occupied by the lateral somitic component expressing cSim 1, a marker for the lateral somite. These results suggest that different thresholds of effective BMP-4 determine distinct subtypes of the mesoderm as a lateralizer during early development.
Insights
Bone morphogenetic protein 4 (BMP-4) is crucial for mesoderm development. Different BMP-4 levels during embryonic development determine specific mesodermal tissue types, influencing somite and lateral plate formation.
Area of Science:
- Developmental Biology
- Molecular Embryology
Background:
- The mediolateral subdivision of mesoderm in early embryos is essential for proper tissue patterning.
- The presomitic mesoderm is not fully committed and can be influenced by cues from the lateral plate.
Purpose of the Study:
- To investigate the molecular mechanisms underlying mesodermal lateralization in chicken embryos.
- To determine if Bone Morphogenetic Protein 4 (BMP-4) acts as a lateralizing cue.
Main Methods:
- Transplantation of presomitic mesoderm into the lateral plate.
- Grafting of COS cells producing BMP-4 into the presomitic region.
- Analysis of gene expression markers (cytokeratin, cSim 1) for mesodermal subtypes.
Main Results:
- Transplanted presomitic mesoderm adopted lateral plate characteristics.
- Exogenous BMP-4 in the presomitic region inhibited somite differentiation and induced lateral plate mesoderm.
- The extent of transformation was dose-dependent on BMP-4 levels, with high levels causing complete conversion and lower levels resulting in mixed somite/lateral plate tissues.
Conclusions:
- BMP-4 acts as a key lateralizing factor in early embryonic mesoderm development.
- Differential thresholds of BMP-4 signaling specify distinct mesodermal subtypes, including somites and lateral plate.
- This study elucidates a critical molecular mechanism controlling embryonic tissue patterning.
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