MIA3 and keratoconus: HSP47, an obligate collagen chaperone was significantly reduced in KC cells,29 2.33 ± 0.29 vs. 1.43 ± 0.25 (Figs. 3B, 3C; Supplementary Fig. S8) Western blots show that CTAGE5/TANGO1,30 required for loading large (>70 nm) cargo into COPII vesicles for export was increased, 0.62 ± 0.07 vs. 1.62 ± 0.12 in KC cell culture extracts (Fig. 3D).