A novel microdissection model for probing cellular interactions. II. LCA and PSA binding sites identified

We use two lectins Lens culinaris agglutinin (LCA) and Pisum sativum agglutinin (PSA), both with alpha D‐mannose and alpha D‐glucose preferential binding specificities, to probe the binding of archenterons and blastocoel roofs microdissected out of 52–54 hr Lytechinus pictus sea urchin embryos, a NIH designated model system. The 24 hour embryos were incubated in each of the lectins (0 (control) – 1 microgram/ml artificial sea water, ASW) for 24–30 hrs in pH 8.0 ASW at 15 degrees C, fixed in 3.7% formaldehyde, dissected and the roofs of the blastocoel and the tips of the archenterons were placed together to determine if the components would bind to each other. Results were either 100% binding or no binding in 15–57 trials for each experiment. LCA treated archenterons bound to untreated roofs, while LCA treated roofs did not bind to untreated archenterons. PSA treated archenterons did not bind to untreated roofs, while PS treated roofs did not bind to untreated archenterons. Experiments were also performed on roofs and archenterons that were both treated with the same or different lectins. In 204 total trials it became clear that lectins with the same general sugar specificities produced sometimes the same and sometimes different results. Although factors such as steric hindrance might account for some effects, the results suggest that alpha D‐mannose and/or alpha D‐glucose may be involved in this cellular interaction and that the saccharide structures in vivo may be complex, binding to one of the lectins and not the other (supported by NIH NIGMS SCORE S0648680, MARC, RISE, the Joseph Drown Foundation, the Sidney Stern Memorial Trust, and CSU Northridge Biology Full Immersion Research Experience (FIRE) course funding; JA and JD equal contributions).