Fig 2: Sulfatase-specific activity and protein expression and protein stability of wildtype FGE upon treatment GALNS protein amount quantification after treatment of MSD primary fibroblasts (variant FGE Gly247Arg homozygous) with tazarotene, bexarotene, and tazarotene/bexarotene in combination for 6 days referred to ß-actin amounts and calculation of GALNS activity based on GALNS protein amount (specific GALNS activity). Data represent mean ± SD three independent experiments (biological replicates). One-way ANOVA followed by Tukey's test for multiple comparisons.Pulse-chase-experiment in HT 1080 FGE wild-type (wt) cells after pretreatment with tazarotene/bexarotene and DMSO (control) for 3 days. Upper panel: autoradiogram of intracellular (full-length FGE, C) and cleaved and secreted (?72 FGE, M) 35S isotope labeled FGE protein in either condition with a chase time of 4 h. Lower panel: Quantification of the autoradiogram, n = 1 experiment. Source data are available online for this figure.

Fig 3: Drug screen and evaluation of positive hit drugs using immortalized MSD patient-derived cells Indicative plot of one 96-well screening plate of the MSD-ARSA high-throughput screening assay with negative and positive controls included. Individual OD values were given for each well (circles) and indicate ARSA activity (gray area: baseline activity). Three hit drugs exceeded the upper baseline OD range. N = 1 experiment per well and drug treatment, final concentration of each drug 10 µM, treatment time 48 h.ARSA activity quantification (nmol/h/mg) after treatment of MSDi cells with a selection of four positive hit drugs at a final concentration of 10 µM on MSDi cells in 25 cm2 cell culture flasks for 3 days. Data represent mean ± SD of seven independent experiments (biological replicates). One-way ANOVA followed by the Tukey's test for multiple comparisons. Difference against negative control: **P < 0.01, ****P < 0.0001. See details on P-values in Appendix Table S3.ARSA activity quantification (nmol/h/mg) after treatment of MSDi cells with increasing concentrations of tazarotene for 3 days. Data represent mean ± SD of 3–9 independent experiments (biological replicates). One-way ANOVA followed by the Tukey's test for multiple comparisons. Displayed are significance levels for the next significant difference between adjacent concentrations. # P < 0.05, ## P < 0.01. Difference against 0 µM control: **P < 0.01, ****P < 0.0001. See details on P-values in Appendix Table S4.GALNS activity quantification after treatment of MSDi cells with increasing concentrations of tazarotene for 3 days. Data represent mean ± SD of four independent experiments (biological replicates). One-way ANOVA followed by the Tukey's test for multiple comparisons. Difference against 0 µM control: **P < 0.01, ***P < 0.001, ****P < 0.0001. See details on P-values in Appendix Table S5.Analysis of different retinoids' potential to restore ARSA activity in MSDi cells in comparison to tazarotene after treatment for 3 days at a final concentration 10 µM of each drug (Adapalene 1 µM). Data represent mean ± SD of three independent experiments (biological replicates). One-way ANOVA followed by the Tukey's test for multiple comparisons. Difference against DMSO control: **P < 0.01, ***P < 0.001, ****P < 0.0001. See details on P-values in Appendix Table S6.ARSA activity quantification after treatment of MSDi cells with increasing concentrations of bexarotene for 3 days. Data represent mean ± SD of 3–10 independent experiments (biological replicates). One-way ANOVA followed by the Tukey's test for multiple comparisons. Displayed are significance levels for the next significant difference between adjacent concentrations. # P < 0.05. Difference against 0 µM control: *P < 0.05, ***P < 0.001, ****P < 0.0001. See details on P-values in Appendix Table S7.ARSA activity quantification after simultaneous treatment of MSDi cells with increasing concentrations of tazarotene and bexarotene in a fixed combination of 1:2 for 3 days. Data represent mean ± SD of 3–6 independent experiments (biological replicates). One-way ANOVA followed by the Tukey's test for multiple comparisons. Displayed are significance levels for the next significant difference between adjacent concentrations. #### P < 0.0001. Difference against 0/0 µM control: ****P < 0.0001. See details on P-values in Appendix Table S8.Analysis and quantification of a time-dependent increase in ARSA activity in MSDi cells simultaneously treated with 10 and 20 µM tazarotene and bexarotene, respectively. Data represent mean ± SD of 3–10 independent experiments (biological replicates). One-way ANOVA followed by the Tukey's test for multiple comparisons. Displayed are significance levels for the next significant difference between treatment times. # P < 0.05, ### P < 0.001, #### P < 0.0001. Difference against 0 days control: *P < 0.05, ****P < 0.0001. See details on P-values in Appendix Table S9. Source data are available online for this figure.

Fig 4: Hit drug evaluation on immortalized MSD fibroblasts ARSA activity quantification (nmol/h/mg) after treatment of MSDi cells in 25 cm2 cell culture flasks with a selection of four positive hit drugs at a final concentration of 10 µM for 6 days. Data represent mean ± SD of seven independent experiments (biological replicates). One-way ANOVA followed by Tukey's test for multiple comparisons. Difference against negative control: ****P < 0.0001. See details on P-values in Appendix Table S31.GALNS activity quantification (nmol/h/mg) after treatment of MSDi cells with a selection of four positive hit drugs at a final concentration of 10 µM for 3 days. Data represent mean ± SD of five independent experiments (biological replicates). One-way ANOVA followed by Tukey's test for multiple comparisons. Difference against negative control: **P < 0.001. See details on P-values in Appendix Table S32.GALNS activity quantification (nmol/h/mg) after treatment of MSDi cells with a selection of four positive hit drugs at a final concentration of 10 µM for 6 days. Data represent mean ± SD of five independent experiments (biological replicates). One-way ANOVA followed by Tukey's test for multiple comparisons. Difference against negative control: * P < 0.05, ** P < 0.001. See details on P-values in Appendix Table S33.ß-galactosidase (betaGAL) activity quantification (nmol/h/mg) after treatment of MSDi cells with a selection of four positive hit drugs at a final concentration of 10 µM for 3 days. Data represent mean ± SD of five independent experiments (biological replicates). One-way ANOVA followed by Tukey's test for multiple comparisons.ß-hexosaminidase A and B (betaHEXAB) activity quantification (nmol/h/mg) after treatment of MSDi cells with a selection of four positive hit drugs at a final concentration of 10 µM for 3 days. Data represent mean ± SD of five independent experiments (biological replicates). One-way ANOVA followed by Tukey's test for multiple comparisons.Dose-response curve of ARSA activity calculated from data displayed in Fig 1C (MSDi cells, tazarotene treatment) by nonlinear regression analysis. Drug concentrations are displayed after transformation into log10 values and baseline activity (negative control, DMSO-only treatment) was manually referred to log-2. Dots and error bars represent mean ± SD.Dose-response curve of GALNS activity calculated from data displayed in Fig 1D (MSDi cells, tazarotene treatment) by nonlinear regression analysis. Drug concentrations are displayed after transformation into log10 values and baseline activity (negative control, DMSO-only treatment) was manually referred to log-2. Dots and error bars represent mean ± SD.Dose-response curve of ARSA activity calculated from data displayed in Fig 1F (MSDi cells, bexarotene treatment) by nonlinear regression analysis. Drug concentrations are displayed after transformation into log10 values and baseline activity (negative control, DMSO-only treatment) was manually referred to log-2. Dots and error bars represent mean ± SD.Dose-response curve of ARSA activity calculated from data displayed in Fig 1G (MSDi cells, tazarotene/bexarotene treatment) by nonlinear regression analysis. Drug concentrations are displayed after transformation into log10 values and baseline activity (negative control, DMSO-only treatment) was manually referred to log-2. Dots and error bars represent mean ± SD. Source data are available online for this figure.