[menzoic]

I’m also surprised that a slight change in C1GalT1 expression has such a big effect on the glycocalyx. That enzyme is notoriously high-capacity, so you’d think it runs at near-saturating levels most of the time. My hunch is that something else in the pathway is hitting a bottleneck, possibly a chaperone like Cosmc that’s needed for proper enzyme folding, or maybe there’s some substrate competition with parallel glycosylation pathways. Once that bottleneck is reached, even a small shift can have an outsized impact on final glycan structures. In mice specifically, there might be unique regulatory quirks that amplify this effect, and you end up with a dramatic change in the mucins even though the enzyme itself seems too powerful to be the limiting step.

[hirenj]

Yes, something along these lines, and maybe the other pathways as the most interesting possibility. I don’t know if there any reports of sTn in older mice, but that would be pretty wild.