Multimodal Characterization of Systems-Level Robustness in the Cellular Organelle Network*

A distinguishing characteristic of eukaryotic cells is their compartmentalization into membrane bound organelles. While each type of organelle has their own individual functions, there are vital cellular processes that come from the interactions between them, such as organelle biogenesis and metabolic regulation. A central question in cellular biophysics is to what degree is cellular function robust or fragile to breaks in the organelle network. Here I aim to address the systems-level role organelle interactions have in regulating organelle composition and metabolic flows. These interactions can be explored by genetically deleting interorganelle protein bridges called organelle contact sites. Using hyperspectral confocal microscopy on a strain of Saccharomyces cerevisiae engineered with fluorescent labels for six types of organelles, we can simultaneously measure organelle size, morphology, and spatial components at a single cell resolution. To investigate metabolic regulation, we take transcriptomic and metabolomic data and infer their fluxes with optimization modeling. The parallel information from microscopy and omics is compared across genetic mutants to highlight altered physiology that stems from perturbations in the network. Our imaging and functional genomics results suggest that mitochondria represent particularly general fragile node in the organelle network, while attendant organelle deficiencies appear in reduced subsets of breaks to the organelle contact network.