Mechanisms of Segment Border Sharpening
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Author

David Wilkinson

Additional Author(s): Qiling Xu

Tools & Techniques: Embryo Manipulation
Embryonic Patterning: Segmentation; Compartments/Boundaries
Morphogenesis: Cell Movements
Signaling: Contact-Mediated Signaling; Signaling Pathways
Ectoderm-derived: Nervous System
Organism: Chick, Mouse
Stage of Development: Embryo

Object Description

The developing vertebrate hindbrain is divided into segments called rhombomeres. Segment identity is established through coordinated expression of a network of transcription factors.  This figure depicts the mechanisms that underlie the sharpening of segment borders in the hindbrain.  Initially, the expression domain borders are fuzzy (distinct cell identity indicated with red versus green), but they eventually become sharp (a). Two mechanisms can contribute to this sharpening: switching of the identity of ectopic cells to that of the new neighbors (asterisked cell in b), or segregation of cells into territory that has the same identity (asterisked cell in c). Evidence for switching comes from transplantation experiments in which it is found that at early (but not late) stages, ectopic single cells will switch identity in the new environment (d). However, when a group of cells is transplanted and remains clustered, these cells do not switch identity (e), suggesting that identity can be affected by local cell interactions.
WIREs Dev Biol 2013. DOI: 10.1002/wdev.106

References

Xu,Q., Wilkinson,D.G. Boundary formation in the development of the vertebrate hindbrain. WIREs Dev Biol, 2013, Published Online: Jan 25 2013.

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