ZBiotech’s heparan sulfate glycan array helps researchers identify the sugar-binding sites of BMP4.

Embryonic stem cells (ESC) differentiate into primary germ layers at the blastocyst stage. One of the key regulators of this process is bone morphogenetic protein 4 (BMP4). BMP4 promotes the differentiation of embryonic stem cells into mesodermal cells by interacting with heparan sulfate (HS). In this study, Naticchia and colleagues hoped to harness the power of synthetic HS glycopolymers to drive specific ESC differentiation into embryoid body structures. They first identified the potential heparan sulfate binding epitopes for BMP4. They then synthesized heparan sulfate glycopolymers and introduced them into the glycocalyx of ESCs. They proved the binding of BMP4 with heparan sulfate glycopolymers in living cells, and this interaction activates the signaling pathways necessary for stem cell differentiation. This proof-of-concept study demonstrates the feasibility of employing synthesized HS glycopolymers to drive specific ESC differentiation into embryoid body structures.

The scientists used our heparan sulfate microarrays to identify the fine heparan sulfate structures to which BMP4 binds. The HS microarray contains a variety of chemoenzymatically synthesized heparan sulfate oligosaccharides. The arrays were first blocked with a 3% bovine serum albumin solution, and then the BMP4 dilution was added. BMP4 bindings were detected with antibodies.

The results showed that BMP4 preferentially binds to HS oligosaccharides with multiple sulfated groups. The strongest associations were found for those with N-O, 2-O-, and 6-O-sulfation motifs. Although 3-O-sulfate modifications of HS are usually responsible for its anticoagulant activity, the addition of 3-O-sulfation motifs weakened the binding of BMP4.

The heparan sulfate glycan array helped  Naticchia and colleagues determine the HS binding epitopes of BMP4. These valuable structural insights lay the foundations for the success of the targeted HS glycopolymer synthesis.