SUMF1 and mucosulfatidosis: To explore whether FGE mediates the response to tazarotene and bexarotene in MSD cells, we used ARPE19 retinal pigment epithelial cells with CRISPR/Cas9 generated SUMF1‐gene knock‐out (ARPE19 SUMF1−/−, Appendix Fig S12) and appropriate controls (ARPE19 wt, MSDi) and treated with increasing concentrations of tazarotene.