engleski

Chip-Based Nanoelectrospray High Capacity Ion Trap Mass Spectrometry of Gangliosides from Precentral vs. Postcentral Gyrus of Fetal Human Brain

Gangliosides are mono- to polysialoglycosphingolipids. Although found in all vertebrate tissues as cell plasma-membrane and glycocalyx components, their concentration and the pattern complexity are the highest in the mammalian brain tissues. Certain gangliosides have been implicated in key brain developmental processes: neuritogenesis, directional cell motility, apoptosis, and cell-cell recognition1, 2. Our group continuously participates in collecting mass spectrometry (MS)-based evidence confirming and characterizing ganglioside patterns of different neuroanatomically (and functionally) defined human brain regions as the region- and the developmental stage-specific. Here, we characterized compositions of native ganglioside mixtures from two functionally defined regions of fetal human brain in 24 weeks of gestation (wg): the precentral gyrus (the location of primary motor cortex) and the postcentral gyrus (the primary somatosensory cortex). For analysis, our recently developed chip-based nanoelectrospray high capacity ion trap MS methodology3 was employed and complemented with high-performance thin-layer chromatographic detection. The selected regions dissected from 24 wg fetal human brain were stored at -20 °C upon analysis. Gangliosides were extracted and purified from the tissue homogenates. The MS screening (MS1) and sequencing (MS/MS) analyses were performed on a High Capacity Ion Trap Ultra (HCT Ultra, PTM discovery) mass spectrometer (Bruker Daltonics, Bremen, Germany) that was, via an in-laboratory made mounting system, coupled with a NanoMate robot incorporating ESI 400 Chip technology (Advion BioSciences, Ithaca, USA) ; the mass spectra were acquired in the m/z range 100-3000, with a scan speed of 8000 m/z per second. More than 100 individual species was detected in each ganglioside mixture by MS1 screening in the negative ion mode. The precentral and postcentral gyrus ganglioside patterns differed in relative abundance of individual species. Mono- and disialylated structures were present with higher abundance in the postcentral comparing to the precentral gyrus. Tetraose-series gangliosides with 1-3 sialic acid residues (GM1/nLM1/LM1, GD1/nLD1, GT1), as typical brain tissue forms, were major structures of both gyri, followed by simpler mono- and disialylated forms (GM3, GD3, GM4, GM2), while GD2 and GT3 were minor. The abundance of fetal brain markers, tetra- and particularly pentasialylated structures, was, as expected, much higher than previously observed in adult human brain ; the same was noticed for fucosylated, O-acetylated and lactonized gangliosides. Most of ganglioside forms with defined oligosaccharide structure were represented by several species differing by the composition of ceramide portion. In spite of very low intensity of most ions arising at higher m/z values, a few ions corresponding to polysialylated species were sequenced and their structural features were characterized. The chip-based electrospray HCT MS analysis enables highly informative characterisation of regions-specific composition of human brain gangliosides.

gangliosides; fetal human brain; chip-based MS

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