Blastocysts don't go it alone. Extrinsic signals fine-tune the intrinsic developmental program of trophoblast cells.
The preimplantation embryo floats freely within the oviduct and is capable of developing into a blastocyst independently of the maternal reproductive tract. While establishment of the trophoblast lineage is dependent on expression of developmental regulatory genes, further differentiation leading to blastocyst implantation in the uterus requires external cues emanating from the microenvironment. Recent studies suggest that trophoblast differentiation requires intracellular signaling initiated by uterine-derived growth factors and integrin-binding components of the extracellular matrix. The progression of trophoblast development from the early blastocyst stage through the onset of implantation appears to be largely independent of new gene expression. Instead, extrinsic signals direct the sequential trafficking of cell surface receptors to orchestrate the developmental program that initiates blastocyst implantation. The dependence on external cues could coordinate embryonic activities with the developing uterine endometrium. Biochemical events that regulate trophoblast adhesion to fibronectin are presented to illustrate a developmental strategy employed by the peri-implantation blastocyst.
Armant
D Randall
DR
Department of Obstetrics and Gynecology, C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, MI 48201-1415, USA. d.armant@wayne.edu
D000818:Animals; D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism; D002448:Cell Adhesion; D002454:Cell Differentiation; D019070:Cell Lineage; D015536:Down-Regulation; D004717:Endometrium / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008954:Models, Biological; D009361:Neoplasm Invasiveness; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction; D013997:Time Factors; D014327:Trophoblasts / Q000166:cytology* / Q000378:metabolism; D014599:Uterus / Q000378:metabolism
D005353:Fibronectins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex