Journal
DEVELOPMENTAL BIOLOGY
Volume 228, Issue 2, Pages 337-349Publisher
ACADEMIC PRESS INC
DOI: 10.1006/dbio.2000.9946
Keywords
craniofacial development; lip morphogenesis; epithelial-mesenchymal transformation; apoptosis of periderm; carboxyfluorescein
Categories
Funding
- NIDCR NIH HHS [R01-DE11142] Funding Source: Medline
Ask authors/readers for more resources
We have previously demonstrated that epithelial-mesenchymal transformation (EMT) brings about TGF beta3-induced confluence of craniofacial primordia that derive from the maxillary processes and give rise to the avian palate. The upper lip of the chick embryo forms by confluence of primordia also derived from the maxillary processes, but in this case, they fuse with the intermaxillary segment of the nasofrontal process. Here, we ask whether the bilateral epithelial seams formed when these primordia contact each other in vivo are removed by apoptosis (as formerly was believed to occur in developing palate) or by EMT. We found that, as is the case in the palate, the periderm of the two-layered embryonic epithelium begins to slough shortly before these primordia fuse, bringing the basal epithelial cells into close contact. We show by TUNEL staining and confirm by TEM that apoptosis occurs only in periderm. TEM reveals that basal epithelial cells contacting each other to form the midline seam produce numerous desmosomes with each other. Then, basement membrane begins to disappear, numerous filopodia extend from the basal surfaces of epithelial cells, the space between them enlarges, and the seam breaks apart, leaving mesenchymal cells in its wake. Transformation of the carboxyfluorescein (CCFSE)-labeled epithelial seam is demonstrated in vivo by detection of CCFSE bodies in mesenchymal cells that replace it. This demonstration of EMT in avian lip development lays important groundwork for understanding the causes of human cleft lip and analyzing the mechanism of action of growth factors, such as SHH and BMPs, that have been shown (J. A. Helms et al., 1997, Dev. Biol. 187, 25-35) to be involved in avian lip confluence. (C) 2000 Academic Press.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available