Concanavalin A and wheat germ agglutinin binding to sea urchin embryo basal laminae

The basal laminae and inner extracellular matrices of Lytechinus pictus and Arbacia punctulata embryos were characterized on the basis of lectin binding. Developmental stage specific patterns of lectin binding were observed after microinjection of Con A-FITC and WGA-FITC. Lectin-specific patterns differed between control, sulfate free sea water (SFSW) and tunicamycin treated embryos. Con A injection resulted in the rounding-up of cells in the epithelium and was most pronounced in embryos cultured in the presence of tunicamycin. Basal laminae were isolated by Triton X-100 extraction of whole embryos. Proteins were separated by SDS-PAGE, electrophoretically transferred to nitrocellulose and incubated in biotinylated lectins. Lectin-binding glycoproteins were detected with avidin peroxidase. The electrophoretic pattern of Con A-binding proteins in early developmental stages of Arbacia was similar with several low molecular weight species appearing at gastrulation in control and SFSW embryos. WGA-binding in Arbacia and Lytechinus control embryos was limited to a 125,000 Mr glycoprotein (gp125). In addition to gp125, several high molecular weight WGA-binding glycoproteins were also detected in SFSW embryos. The evidence suggests that mesenchyme migration and gastrulation are correlated with changes in the molecular composition of the ECM.