Fig. 4

MALDI-TOF mass spectra of permethylated transferrin N-glycans in SLC39A8-CDG Patient-1 compared to a reference control, showing the spontaneous amelioration of the glycosylation profile over a four-years period. Transferrin N-glycan analysis in a paediatric representative control (a). Transferrin N-glycan analysis conducted on Patient-1 at 3 years of age (b), reveals a marked increase of the monosialo-biantennary glycoform at m/z 2431.2 (A2G2S1) and the occurrence of the monosialo- monogalacto-biantennary glycan at m/z 2227.1 (A2G1S1). Minor amounts of other truncated glycoforms are also detected. Serum transferrin MALDI-TOF MS analysis of Patient-1 at age of 7 years (c) shows a significant spontaneous improvement, with a drastic reduction of all the defective species. Compared to control, the observed glycan increases are outlined by red marks. Glycan structures were assigned following consortium for functional glycomics guidelines: N-acetylglucosamine, blue square; mannose, green circle; galactose, yellow circle; sialic acid, purple lozenge; fucose, red triangle