Advanced mass spectrometry imaging to identify the biological mechanisms underlying the functions of surface lipids in Drosophila

The skin of animals, from humans to Drosophila, is coated with a complex layer of lipids that have a range of functions including minimising trans-epithelial water loss and also providing a barrier against microbial infection. It is not yet clear which lipid species are anti-microbial and which prevent dehydration. Recent research in our lab has also identified a novel function of these lipids in Drosophila; certain classes have been shown to be autotoxic, however the biological mechanism underlying this is not yet fully understood. These questions represent a significant metrological challenge, and to answer these we will use the 3D OrbiSIMS. This novel imaging mass spectrometry instrument combines high lateral resolution and mass accuracy to provide detailed spatial information about the chemical composition of the sample which is not possible using existing techniques. The development of ambient and cryogenic methodology for biological samples using this instrument will provide great progress to the field of biological imaging. In particular, the cryo-SIMS methodology developed will be critical for the accurate measurement of biological samples providing a state as close to native as possible to reduce experimental artefacts.

The aims and objectives of this project are to:
Develop 3D OrbiSIMS imaging methodology for lipids and metabolites on the Drosophila cuticle. This involves the development of cryogenic sample preparation methods.
Develop data analysis pipelines for identification of lipids and small molecules using the high mass resolving power and mass accuracy, as well as MS/MS capacity for increased assignment confidence.
Identify the function of different lipid species, and the biological mechanism via which certain species can cause toxicity.

Imaging mass spectrometry methodology will be developed using the 3D OrbiSIMS at the National Physical Laboratory. This instrument integrates the high lateral resolution of ToF-SIMS and the high mass resolving power and mass accuracy of an Orbitrap analyser with MS/MS capabilities, alongside 3D depth-profiling and image reconstruction to create a 3D chemical image of the sample. We will use this technique, combined with the power of Drosophila genetics, to answer key questions on the role of cuticular lipids.

This research aligns with the EPSRC's Healthcare Technologies strategy to develop cross-cutting research capabilities, in particular the development of novel imaging techniques. The development of 3D OrbiSIMS lipid and metabolite imaging will provide unparalleled 3D chemical imaging of biological samples with combined high lateral resolution and mass resolving power. The use of this cutting-edge technique to investigate the distribution and function of Drosophila cuticular lipids fits well into the Analytical Science research area of the EPSRC which is interested in the development of novel techniques to analyse biological matter and systems.

This research is a collaboration between the Francis Crick Institute providing the biological expertise, and the National Physical Laboratory providing the expertise in imaging mass spectrometry.