Critical Reviews in Oral Biology & Medicine, Vol 4, 67-72, Copyright © 1992 by International & American Associations for Dental Research
Current concepts in embryonic craniofacial development
G. H. Sperber
Department of Oral Biology, University of Alberta, Edmonton, Canada.
Embryology mirrors phylogeny. The phenotypic expression of the genome is
the result of differential gene transcription, the critically timed turning
on and off of specific genes by transcription factors to produce cyto-,
histo-, and morpho-differentiation that fleetingly reflects evolutionary
stages of development during ontogeny. Hox genes regulate transcription of
other structural genes and are responsible for patterning of the facial
primordia. Cephalic development involves extremely complex morphogenetic
mechanisms built on conserved elements that have undergone enormous
evolutionary changes. Transient expression of phylogenetic origins
characterize ontogeny and are reflected in defective development that may
be due to inappropriate expression of Hox genes or distorted or disrupted
epignetic processes. The mechanisms by which genetic information is
transformed into morphological patterning by the actions of growth factors,
morphogenes, and receptors are currently being identified. Biochemical,
immunological, and allometric analyses of embryos and fetuses in
experimental and descriptive studies are elucidating details of units of
craniofacial morphogenesis--faciogenesis, palatogenesis, gnathogenesis,
odontogenesis. Three-dimensional model computer-assisted reconstruction of
sectioned embryos and fetuses provides a further technique for
understanding the complex configurations of tissue migratory patterns and
growth sites that account for normal and abnormal craniofaciogenesis.
