Microinjection of antifibronectin antibodies in the chicken blastoderm: inhibition of mesoblast cell migration but not of cell ingression at the primitive streak.
The involvement of fibronectin in adhesion and migration of individual mesoblast cells during chicken gastrulation was examined after microinjection of functional and nonfunctional antifibronectin antibodies in the blastoderm during the period of rapid migration of mesoblast cells. The injection of affinity-purified polyclonal antihuman fibronectin antibody (total IgG or Fab fragment) or of monoclonal antichicken cellular fibronectin caused a thickening of the primitive streak, which was composed of loosely connected cells. This effect was most evident at the level of Hensen's node, and very few mesoblast cells were observed migrating in the space between upper layer and deep layer. The obvious explanation of this effect was that the de-epithelialization of upper layer cells persisted in the presence of antibodies, but ingressed cells failed to emigrate from the primitive streak. Immunostaining of microinjected antibodies showed binding to the basement membrane, to the cell surface of mesoblast cells that had migrated before microinjection occurred, and to the cell surface of deep layer cells. Cells that ingressed and detached in the course of reincubation of the embryo possessed little immunolabelling along their cell surface. The results suggest that the failure of ingressed cells to emigrate from the primitive streak and to form mesoblast was due (1) to alterations in adhesion between newly ingressed primitive streak cells, which had the ability to detach but possessed relatively little fibronectin along their cell surfaces and a small number of cell protrusions, and (2) probably to a lack of adhesion of detached cells to the basement membrane, which was blocked by the presence of antifibronectin antibodies. We conclude that the presence of fibronectin in the basement membrane is required for emigration of ingressed cells and migration of mesoblast cells to occur. Once migration has commenced, fibronectin is also deposited along the cell surface of migrating cells, a factor that may increase their mutual adhesion.
Harrisson
F
F
Department of Human Anatomy and Embryology, University Centre of Antwerp, Antwerpen, Belgium.
Van Nassauw
L
L
Van Hoof
J
J
Foidart
J M
JM
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000008:administration & dosage*; D001756:Blastoderm / Q000166:cytology* / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002642:Chick Embryo; D005353:Fibronectins / Q000276:immunology* / Q000502:physiology; D008845:Microinjections
D000888:Antibodies, Anti-Idiotypic; D005353:Fibronectins