3D MALDI Mass Spectrometry Imaging of a Single Cell: Spatial Mapping of Lipids in the Embryonic Development of Zebrafish

Maria Emilia Dueñas,Jeffrey J Essner,Young Jin Lee

doi:10.1038/s41598-017-14949-x

Abstract

The zebrafish (Danio rerio) has been widely used as a model vertebrate system to study lipid metabolism, the roles of lipids in diseases, and lipid dynamics in embryonic development. Here, we applied high-spatial resolution matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry imaging (MSI) to map and visualize the three-dimensional spatial distribution of phospholipid classes, phosphatidylcholine (PC), phosphatidylethanolamines (PE), and phosphatidylinositol (PI), in newly fertilized individual zebrafish embryos. This is the first time MALDI-MSI has been applied for three dimensional chemical imaging of a single cell. PC molecular species are present inside the yolk in addition to the blastodisc, while PE and PI species are mostly absent in the yolk. Two-dimensional MSI was also studied for embryos at different cell stages (1-, 2-, 4-, 8-, and 16-cell stage) to investigate the localization changes of some lipids at various cell developmental stages. Four different normalization approaches were compared to find reliable relative quantification in 2D- and 3D- MALDI MSI data sets.

Highlights

Traditional analytical approaches to study small metabolites and lipids require extensive sample preparation, laborious extractions, derivatizations, and previous knowledge of compounds of interest
Odd number serial sections were analyzed in negative ion mode with DAN as a matrix, and even number serial sections were analyzed in positive ion mode with the binary matrix of DHB/Fe3O4 as a matrix. This will reduce the sample preparation time involved in the selection of the embryo, cryo-sectioning, and microscope inspection, and minimize the sample-to-sample variation
The work described demonstrates, for the first time, that high-resolution matrix-assisted laser desorption/ionization (MALDI)-Mass spectrometry imaging (MSI) can be applied for three dimensional chemical imaging of a single cell

Summary

Introduction

Traditional analytical approaches to study small metabolites and lipids require extensive sample preparation, laborious extractions, derivatizations, and previous knowledge of compounds of interest. TOF-SIMS has been utilized for 3D MSI of single cells[19,20], especially incorporating depth profiling as a way to achieve z-directional information; high mass compounds that can be analyzed by TOF-SIMS have been mostly limited to exogenous drug compounds due to significant fragmentations In this analysis, we performed 3D MALDI-MSI on single zebrafish zygotes by acquiring MS imaging data set in positive and negative ion mode for alternative slides of 62 consecutive cross-sectional tissue sections. We performed 3D MALDI-MSI on single zebrafish zygotes by acquiring MS imaging data set in positive and negative ion mode for alternative slides of 62 consecutive cross-sectional tissue sections This allows for 3D visualization of more comprehensive lipid species from a single cell. Full-scan MSI and MS/MS were acquired for embryos at different cell stages (1-, 2-, 4-, 8-, and 16-cell stage) to investigate the changes in phospholipid distribution during the early stages of zebrafish development

Methods

Results

Conclusion