Cell adhesion to extracellular matrix in normal Rana pipiens gastrulae and in arrested hybrid gastrulae Rana pipiens female X Rana esculenta male.

Rana pipiens eggs fertilized by Rana esculenta sperm (ESC) hybrid embryos develop until gastrulation in control Rana pipiens embryos (PIP) and then show morphogenetic arrest. After arrest, ESC do not gastrulate but live for 5 days as blastula-like embryos. We studied the distribution of fibronectin (FN)-containing fibrils and integrin (INT) in PIP and ESC. There are many FN-fibrils in PIP organized in anastomosing networks radiating away from the center of individual cells and across intercellular boundaries. ESC have fewer fibrils compared to PIP. These fibrils are first located between cells in disorganized arrays. After arrest in ESC, when PIP are Stage 14 neurulae, many more FN-fibrils appear. INT-staining occurs in both embryos in similar patterns. In xenoplastic transplantations, we found that the extracellular matrix on the inner surface of the ESC blastocoel roof serves as a substratum for PIP cell migration. In an in vitro assay, we found more cell adhesion to FN-substrata in PIP than in ESC. Cell locomotion rates on FN-substrata were 1.70 +/- 0.85 microns/min for PIP but only 0.46 +/- 0.56 microns/min for ESC. We also found that the inner surface of the blastocoel roof from ESC can not promote cell adhesion and locomotion when Stage 11 fragments are used for conditioning but that Stage 14 fragments can deposit a FN-fibril-rich extracellular matrix which supports PIP mesodermal cell migration at a rate of 1.26 +/- 0.38 microns/min.