(C) Transmission electron microscopy (TEM) of crypts of COPS8fl/fl and COPS8ΔIEC mice. The base of the crypt in COPS8ΔIEC mice is occupied by poorly differentiated columnar epithelial cells that lack secretory granules, rudimentary electron-dense granules (black arrows), granules in the lumen (blue arrows) and have a contracted endoplasmic reticulum (ER) (white arrows). Scale bar 5μm, data are from seven biological replicates per genotype. 