Endosome dynamics in MEFs stably expressing GFP-SNX1. Representative examples of MEFs stably expressing GFP-SNX1, derived from Spastinwt/wt (left), Spastinwt/N384K (center), or SpastinN384K/N384K (right) animals. Note the development of elongated GFP-SNX1 tubules in the SpastinN384K/N384K MEFs that are slow to break from the parent endosome. Insets show a higher-magnification view of endosomal tubule fission events indicated by boxes in the main videos.