In order to investigate the potential role of all three S1P-metabolizing enzymes in HD cellular homeostasis, we undertook pharmacological studies (Fig. 9D) in mice striatal-derived knock in cell lines expressing endogenous levels of wild type (STHdh7/7) or mHtt (STHdh111/111) and where levels of S1P have been previously reported to be reduced32. Here, MBTPS1 is linked to Huntington disease.