Unravelling neuronal and glial differences in ceramide composition, synthesis, and sensitivity to toxicity.

Ceramides are lipids that play vital roles in complex lipid synthesis, membrane function, and cell signaling. Disrupted ceramide homeostasis is implicated in cell-death and several neurologic diseases. Ceramides are often analyzed in tissue, but this approach fails to resolve cell-type differences in ceramide homeostasis that are likely essential to understanding cell and non-cell autonomous contributions to neurodegeneration. We show that human iPSC-derived neurons and glia differ in their rate of ceramide synthesis, ceramide isoform composition, and responses to altered ceramide levels. RNA-sequencing of cells treated to increase or decrease ceramides revealed connections to inflammation, ER stress, and apoptosis. Moreover, introducing labeled sphinganine showed that glia readily synthesize ceramide de novo and that neurons are relatively more sensitive to ceramide toxicity. Our findings provide a framework for understanding neurologic diseases with sphingolipid alternations and insights into designing therapeutics that target ceramide for treating them.