N-glycosylation consists in the addition of a glycan precursor onto a nascent protein in the endoplasmic reticulum. This glycan is then trimmed and matured in the Golgi by addition of various sugars motifs, leading to a large heterogeneity of glycans structures, from site to site or on the same glycosylation site. Until now the underlying causes of this micro-heterogeneity have not clearly been id ...