First published online May 30, 2007
Development 134, 1203e (2007)
© The Company of Biologists Limited
VEGF to the bones
Spicules - mineralised rods that constitute the sea urchin skeleton - form
from a small number of primary mesenchymal cells (PMCs). During gastrulation,
these PMCs locate along the ectodermal wall in a stereotypical pattern that
determines skeletal morphology. As yet unknown guidance cues from the ectoderm
are thought to control PMC positioning. VEGF/VEGFR signalling between the
ectoderm and PMCs is now shown by Christian Gache's lab on
p. 2293 to be the
missing link that directs PMC migration and, thus, skeletal morphology. While
VEGFR is expressed in PMCs, its ligand, VEGF, is expressed in the overlying
ventrolateral ectoderm. Impaired VEGFR signalling perturbs PMC positioning
(and spicules subsequently don't form), whereas VEGF overexpression results in
skeletal abnormalities. Ectopically expressing VEGF in embryos in which
endogenous VEGF expression is blocked restores spicule formation. These and
other findings reveal that localized VEGF acts as both a guidance cue and
differentiation signal, providing a crucial link between the positioning and
differentiation of PMCs and embryonic skeletal morphogenesis.

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Related articles in Development:
- Localized VEGF signaling from ectoderm to mesenchyme cells controls morphogenesis of the sea urchin embryo skeleton
- Louise Duloquin, Guy Lhomond, and Christian Gache
Development 2007 134: 2293-2302.
[Abstract]
[Full Text]