Biomedical Engineering Reference
In-Depth Information
from maternal genome control to zygomatic genome with cell-cell adhesion and
intercellular communication and adhesion molecules playing an important role
in regulating embryonic cell development. h is is a concept that has been clearly
demonstrated by immunohistochemistry. Figure 6 uses immunohistochemistry
to demonstrate a 4-cell embryo being held together by adhesion molecules. As
the embryo grows, the adhesion molecules disappear, the cells rearrange and
the adhesion molecules return to hold the cells together. h e polarization and
compaction of morula stage blastomeres leading to dif erentiation towards
trophectoderm and inner mass seem to be closely linked with the formation and
maintenance of calcium-dependent adhesion molecules on their surfaces (Reima
1990).
Fig. 6
Cell adhesion in the early embryo. E-cadherin adhesion of 4-cell hamster embryos. As the
embryo grows, the adhesion molecules disappear, the cells rearrange and the adhesion molecules
return to hold the cells together. Reprinted from Trejo
et al.
(2008), with permission.
Later Embryological Development
During tissue-organ system formation, cells undergo an epithelial-to-
mesenchymal transition where the cells lose cell-to-cell contact mediated by
adhesion molecules, reorganization of the cytoskeleton and the acquisition of a
motile character (Taneyhill 2008). Following migration to their ultimate location,
the cells coalesce once again and regain their adhesion molecules. As the neural
tube forms and separates from the overlying ectoderm, it loses E-cadherin
and acquires N-cadherin, but the ectodermal cells that were originally above it
continue to express E-cadherin. As the cells migrate to their adult site, they lose
