Speaker: Akos Vertes, The George Washington University
Topic: Spatial Metabolomics of Single Cells in their Natural Environment
Date: February 3, 2025
Time: 6:15 pm Dinner, 7:15 pm Presentation
Location: Shimadzu Scientific Instrument, Inc. Training Center 7100 Riverwood Drive, Columbia, MD 21046 (Directions)
Dinner: Please RSVP to Dingyin Tao (owendtao@gmail.com) by Friday, January 31 if you will be attending the dinner.
Abstract: In multicellular organisms, cells assemble into tissues with specific functions. Tissue embedded cells operate a selection of metabolic pathways for the synthesis and degradation of a collection of small molecules that serve growth, signaling, and reproduction. Capturing the spatiotemporal distributions of metabolites, including lipids, with cellular granularity gives new insight into the functioning of tissues. We have developed ambient ionization techniques that can report on the metabolite content of functioning cells with high throughput and targeting capabilities. Image analysis and morphometry of brightfield and fluorescence microscope images is used to target selected cell types, followed by mid-IR laser ablation of individual cells. The ablation plume is ionized by an electrospray (laser ablation electrospray ionization, LAESI). Ion mobility separation (IMS) of the produced ions is followed by time-of-flight or Fourier transform ion cyclotron resonance mass spectrometry (MS) for the determination of cellular metabolite abundances. Cell-type specific small molecule compositions are determined and correlated with active metabolic pathways characteristic to cellular functions. Metabolite abundance distributions reflect population heterogeneity through metabolic noise levels and reveal hidden cellular phenotypes segregated into subpopulations functioning in specific metabolic states. Examples of spatial metabolomics are presented for various cell types including human hepatocytes, Arabidopsis thaliana and Allium cepa epidermal cells, and root nodule cells of Glycine max in nitrogen fixing symbiosis with Bradyrhizobium japonicum. In addition, using MS imaging (MSI) based on MALDI and laser desorption ionization (LDI) from silicon nanopost array (NAPA) nanophotonic platforms, the presence of a wide array of cyclic oligohexoses was discovered in the root nodules with degrees of polymerization in the 2 ≤ n ≤ 14 residue range. The spatial distributions of cyclic oligohexoses in the G. max nodules were established by NAPA-LDI-MSI. They appeared more concentrated at the edge of the infection zone or inner cortex and in the stem. At some locations, possibly in the vascular bundles surrounding the nodule and traversing the stem, the cyclic oligohexoses were especially abundant. At the same time, acyclic oligohexoses with 2 ≤ n ≤ 10 were also detected, and their distributions in the nodule sections were mapped. These linear or branching molecules were abundant in the infection zone, where the cyclic oligohexoses were less concentrated or absent.