Advanced profiling and structural analysis of anencephaly gangliosides by ion mobility tandem mass spectrometry

Anencephaly, the most severe type of neural tube defects (NTDs) in humans, occurs between the third and fourth gestational weeks (GW), involves the cranial part of the NT and results in the absence of the forebrain and skull. Exposed to amniotic fluid toxicity, neural tissue is degraded and prevented from development. Currently, little is known about the molecular bases of the disease and the possible involvement of glycans. In this context, considering the role played by gangliosides (GGs) in fetal brain development and the previous achievements of ion mobility separation (IMS) mass spectrometry (MS) in biomarker discovery, we report here on the introduction of this advanced analytical technique in NTD research, and its optimization for a comprehensive determination of anencephaly gangliosidome. Three native GG extracts from residual brains of anencephalic fetuses in 28, 35 and 37 GW were comparatively profiled by IMS MS, structurally analyzed by IMS MS/MS, and finally assessed against a native GG mixture from normal fetal brain. IMS MS provided data on 343 anencephaly gangliosides vs. only 157 known before and revealed for the first time the incidence of the entire penta-to octasialylated series. The comparative assay disclosed variations in GG expression with fetal age and a correlation of the pattern with the developmental stage. In contrast to the normal fetal brain, the neural tissue in anencephaly was found to contain an elevated number of polysialogangliosides and a lower expression of O-Ac- and GalNAc-modified glycoforms. These species worth further detailed investigation as new potential anencephaly markers.