To analyze the effect of DM1 mutation on glial cell physiology, we generated MIO-M1-derivative cell lines expressing a DMPK minigene harboring 0 CTG repeats [MIO-M1-CTG(0)] or an expanded repeat [MIO-M1-CTG(648)], in an inducible manner (Figure S1A). Here, DMPK is linked to myotonic dystrophy type 1.