出版社：American Society for Biochemistry and Molecular Biology
摘要：Gangliosides are glycan-lipid hybrid metabolites that play both structural and signaling roles within a cell (1). Although they were named after the
cell body where they were first discovered, they are particularly abundant in the central nervous system and account for 10% of lipid mass in the
brain (1). Defects in ganglioside metabolism result in metabolic pathologies in multiple neurological disorders, such as being implicated in Alzheimer’s
disease pathogenesis by binding to b-amyloid and amyloid precursor protein (2). Recently, MALDI-MS has been employed to study gangliosides
with significant improvement in detection and imaging of their spatial distribution (3). Despite recent advancements, a consistent hurdle
has been the inability to uniformly deposit matrix crystals. This obstacle limits both sensitivity and image resolution. Recently, 32 combinations of
temperature-controlled, accelerated-velocity robotic matrix spraying were tested on kidney samples to improve these parameters (4). Based on this
workflow, we optimized parameters for matrix deposition to generate high-resolution MALDI images of gangliosides. Fresh frozen C57BL/6J mouse
brain was sectioned at 10 mm (~ −1 mm Bregma), dehydrated under vacuum, and the MALDI matrix a-Cyano-4-hydroxycinnamic acid (7.0 mg/ml)
was applied by an HTX-M5 robotic dry-sprayer with a heated nozzle (79°C) at a spray velocity of 1,300 m/min (A). Images were acquired at a pixel
size of 50 mm using a Waters Synapt G2Si Mass Spectrometer with a mass range of 1000–2500 m/z (A and B). Our analyses demonstrate that gangliosides
are predominantly localized in the cortex and hippocampus of mouse brain, but with notable differences in abundance and localization between
specific brain regions (B and C). For example, a coronal view of the whole brain reveals differential cortex localization for GM1 18:1/18:0
and 20:1/18:0, two of the most abundant ganglioside subtypes (C). GM1 18:1/18:0 is most abundant in the piriform, amygdala nucleus, and striatum,
while 20:1/18:0 is localized in the anterior region in layer 1 and 2 of primary and supplemental somatosensory and dorsal auditory areas.
Magnified analysis (3×) reveals a unique localization for each subtype in different cell layers of the hippocampus. GM1 18:1/18:0 is most abundant
in the CA1 layer of Ammon’s horn and the polymorph layer of the dentate gyrus, whereas 20:1/18:0 resides in the molecular layer of the dentate
gyrus. These data suggest divergent functional roles for these two gangliosides. The ability to accurately quantitate gangliosides with high spatial
resolution will be crucial to interrogating their functional roles in multiple neurological disorders.
