Fig. 3. BECLIN1 is critical for maintaining the specialized functions of secretory intestinal epithelial cells.

FFPE sections of small intestines were stained for the anti-microbial proteins lysozyme (Lyz) and intestinal alkaline phosphatase (IAP) produced by both Paneth and enterocytes, respectively. a Dashed lines delineating the borders of Paneth cells demonstrate the significant morphological abnormalities of lysozyme-containing secretory granules from both Becn1^ΔIEC and Atg7^ΔIEC animals, though the defects in the absence of BECLIN1 are far more pronounced. b Graphical representation of the morphological classifications of abnormal secretory granules in Paneth cells. Villus-associated enterocytes deficient for BECLIN1 demonstrate c almost absent IAP expression or where IAP is present, d diffuse cytoplasmic staining (black arrows) as opposed to well-defined membrane localization. e Representative transmission electron microscopy (TEM) images of Becn1^ΔIEC and Becn1^wtIEC enterocytes reveal distorted mitochondria (m) and electron-lucent tubulated structures characteristic of swollen ER (e) and ER stress in the former. All data represent at least n = 4 biologically independent mice per genotype from n = 3 independent experiments. Graph in b shows the mean ± S.D.