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Glycoproteins responsive to the neural-inducing effect of concanavalin A in Cynops presumptive ectoderm
Abstract:
To examine the possible occurrence of receptors in the ectodermal cell surface which apparently mediates the neural-inducing stimulus, a further experiment by using Con A was done in combination with the enzyme treatments. The presumptive ectoderm explants of Cynops gastrula were first treated with neuraminidase to remove sialic acid. Prior to the Con A treatment, the explants were treated with almond glycopeptidase, which cleaves the asparagine linkage between protein and oligosaccharide in glycoprotein and releases the oligosaccharide moiety intact containing mannose residue from the substrate. No neural induction occurred. When the explants were not treated with almond glycopeptidase, the neural induction frequency was found to be the same as that of the explants treated with only Con A. Biochemical analyses showed that when the fixed ectoderm explants were treated with almond glycopeptidase, several oligosaccharides were released and then fractionated by means of Bio-Gel P-4 filtration. Based on the strict specificity of almond glycopeptidase, these oligosaccharides are unmistakably asparagine-linked oligosaccharides with mannose residues. We discuss the hypothesis of involvement of glycoproteins in the first step of molecular events in the neural induction mechanism.
Insights
This study investigated glycoproteins in neural induction. Removing specific oligosaccharides with almond glycopeptidase blocked neural induction, suggesting glycoproteins are crucial for this early developmental process.
Area of Science:
- Developmental Biology
- Molecular Biology
- Cell Biology
Background:
- Neural induction is a critical early developmental process.
- The cell surface receptors mediating neural induction are not fully understood.
- Glycoproteins are implicated in cell-cell interactions and signaling.
Purpose of the Study:
- To investigate the role of cell surface glycoproteins in mediating neural induction.
- To identify specific molecular components involved in the initial steps of neural induction.
Main Methods:
- Presumptive ectoderm explants from Cynops gastrula were used.
- Enzyme treatments, including neuraminidase and almond glycopeptidase, were applied to explants.
- Concanavalin A (Con A) was used in combination with enzyme treatments.
- Biochemical analyses, including Bio-Gel P-4 filtration, were performed on released oligosaccharides.
Main Results:
- Treatment with almond glycopeptidase, which cleaves asparagine-linked oligosaccharides, prevented neural induction.
- Neural induction occurred when explants were not pre-treated with almond glycopeptidase before Con A exposure.
- Biochemical analysis confirmed the release and characterization of mannose-containing asparagine-linked oligosaccharides.
Conclusions:
- Asparagine-linked oligosaccharides on cell surface glycoproteins appear to be involved in the initial molecular events of neural induction.
- These findings support a hypothesis implicating glycoproteins in the early stages of neural induction mechanism.