Follicle cell death in ovaries from Ddr2slie/slie mutants. Histological sections of ovaries from wild-type (+/+) and Ddr2slie/slie mutant at 10 wk stained with hematoxylin and eosin (A, C), and TUNEL analyses of ovaries (B, D) after treatment with PMSG + hCG. Higher counts of apoptotic follicles were observed in Ddr2slie/slie mutant mice compared with wild-type per ovarian section (E). HE, hematoxylin and eosin; TUNEL, terminal deoxynucleotidyl-transferase-mediated deoxyuridine triphosphate nick end labeling. *P < 0.01; Scale bar, 200 μm.