E. EATR assay in chondrocytes with indicated genotypes (ctrl=wild type) showing % of cells with acidified ER measured by FACS. FGF18 was used at 50 ng/mL overnight. Mean +/- standard error of the mean (sem) of N=4 biological replicates. Analysis of variance one way (ANOVA) p<0.0001: Tukey's post hoc test ***p<0.0005; *p<0.05; NS not significant. 