Age‐ and region‐dependent redistribution of con A binding sites on chick wing‐bud mesoderm cells

Abstract

AbstractThe distribution of concanavalin A (con A) binding sites on chick wing‐bud mesoderm cells from two different developmental stages and from different regions of the same embyronic limbs was examined. Fluorescein isothiocyanate (FITC)‐labeled con A binding sites on mesoderm cells from whole stage 19–20 and the distal third of stage 25 limbs redistributed from a random array over the cell surface to form clusters or caps of binding sites. In contrast, a significantly smaller percentage of developmentally “older” mesoderm cells from the proximal third of stage 25 limbs underwent redistribution of bound con A from its normal random arrangement. In order to further examine the basis for the decrease in con A redistribution in the stage 25 proximal cells, this segment was subdivided into a core (presumptive chondrogenic) and peripheral (presumptive myogenic) region. The results of con A redistribution studies utilizing these two cell populations indicate that a significantly smaller percentage of the core cells are capable of forming clusters or caps. Likewise, in agglutination studies, core cells proved significantly less susceptible to con A‐induced agglutination. These findings indicates that the differences in agglutination and con A redistribution, seen when comparing the proximal cells with the other cell populations, is attributable to a subpopulation of the proximal cells, specifically, those located in the chondrogenic core region. Since the proximal core and peripheral cells are of the same developmental age, these findings suggest that developmental age is not solely responsible for the differences reported here. Thus, prospective phenotype appears also to be involved in the decreased agglutination and a con A redistribution of the chondrogenic core cells.