Adhesion between the archenteron tip and blastocoel roof in the NIH designated sea urchin embryo model is a cellular interaction that has interested investigators for over a century, but its molecular basis is not understood. Here we microdissect the two components of this cellular interaction and use alpha methyl mannose to map molecular groups that may be involved in mediating the cellular interaction. Whole 48–54 hour fixed Lytechinus pictus embryos were washed three times and then dissected in pH 8.0 artificial sea water (ASW), 15°C. The roofs of the blastocoel and the tips of the archenteron were put together and observed to stick together. In over 50 separate trials using bound sets of roof and archenterons attached together, either 0.2 M or 1.0 M alpha methyl mannose was added to the pieces. The pieces remained together. However in 100% of the cases, manually separating the pieces in alpha methyl mannose at either molarity resulted in blocking the rebinding of the blastocoel roofs and archenteron tips.Re‐binding occurred in the absence of the sugar. The results suggest that alpha methyl mannose binding receptors are involved in mediating the cellular interaction. These studies offer a novel approach to map glycans and glycan binding partners that may be functionally important. By microdissecting the components of cellular interactions out of the embryo proper, these components can be probed in pristine media away from factors in intact embryos that could confuse results (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).

Past studies have examined the inhibition of binding of mannose‐rich yeast to immobilized concanavalin A (Con A) in the presence and absence of specific saccharides. This is a model system for testing potential drugs that could block pathogen binding to human cells. Here 2.0M, 0.2 M and 0.02 M NaCl and KCl were tested in a much more extensive study than in the past, for their ability to inhibit binding of yeast (Saccharomyces cerevisiae) to immobilized Con A over a 30 min time course. In about 15,000 replicate experiments, both salts inhibited binding in a nearly identical way, in a concentration dependent manner, ranging from about 20% to about 60% reduced binding over controls. The salt effects reached a plateau at 20‐30 minutes, with 2.0 M salt showing the greatest inhibitory effects. These results are similar to those obtained in studies with specific saccharides, suggesting that salt effectively can block lectin‐saccharide binding, with possible implications in pathogen binding to human cells (Supported by NIH NIGMS SCORE (S0648680), MARC, RISE, the Joseph Drown Foundation and Sidney Stern Memorial Trust.

The adhesion between the NIH model sea urchin embryo roof of the blastocoel and tip of the archenteron is a cellular interaction that has interested investigators for over a century, yet its molecular basis is unknown. Here, 102 blastocoel roofs and archenterons were microdissected out of 102, 54 hr Lytechinus pictus embryos that adhered to each other when placed together. 25 mg per ml free mannan was added to the adhered roofs and archenterons. They remained adhered and then were pulled apart and placed together again in the free mannan solution. All 102 roofs and archenterons adhered once again, the mannan possibly bridging mannan‐binding receptors on both components. As reported in Part III of these studies, mannan conjugated agarose beads also adhered to the dissected roofs and archenterons and here this work was extended to 65, 54 hr L.pictus embryos. Part I of these studies indicated that alpha methyl mannose blocked the cellular interaction. Part II of these studies showed that mannose‐binding lectins could block the interaction. Taken together, this set of studies suggests that mannose‐containing glycans and mannose‐binding receptors may be involved in the cellular interaction between the archenteron and blastocoel roof. This microdissection method, that removes the components of adhesive events from intact embryos, is novel and likely to lead to a better understanding of the molecular basis of cellular interactions (supported by NIH NIGMS SCORE S0648680, MARC, RISE, the Joseph Drown Foundation, the Sidney Stern Memorial Trust, and CSU Northridge Biology FIRE course funding).