TSC1 and dry eye syndrome: To verify the role of ceramide production in KC death, KCs deficient for protein phosphatase 2 A catalytic subunit α (PP2Acα) were incubated with Tsc1-/- hepatocyte-derived CM for 48 h: PP2A cα ablation in KCs attenuated the cell death induced by Tsc1-/- hepatocyte-derived CM (Supplementary Fig. 4).