Molecular Info® Copy Right © 2001
Institute of Molecular Development LLC
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Noggin and retinoic acid transform the identity of avian
facial prominences
S.-H. LEE, K. K. FU, J. N. HUI & J. M. RICHMAN
The Nature, December 2001, 414: 909 - 912.
The signals that determine body part identity in vertebrate embryos are largely unknown,
with some exceptions such as those for teeth and digits. The vertebrate face is derived
from small buds of tissue, facial prominences, that surround the embryonic oral cavity. In
chicken embryos, the skeleton of the upper beak is derived from the frontonasal mass and
maxillary prominences. Bone morphogenetic proteins (Bmps) and the
vitamin A derivative, retinoic acid (RA), are used to specify the identity of the frontonasal
mass and maxillary prominences. Implanting two beads adjacent to the stage-15
presumptive maxillary field, one soaked in the Bmp antagonist Noggin and one soaked in
RA, induces a duplicate set of frontonasal mass skeletal elements in place of maxillary
bones. The duplicated beak is due to transformation of the maxillary
prominence into a second frontonasal mass and not due to ectopic migration of cells or
splitting of the normal frontonasal mass. Thus the levels of Bmp and RA determine
whether specific regions of the face form maxillary or frontonasal mass derivatives.
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