Tenm4m1cells lack the ability to differentiate. Cell proliferation of the epiblast is affected during gastrulation as evidenced by immunostaining of BrdU in wildtype (A) and Tenm4m1/m1(B) embryos at E6.5. Since sections were counterstained with hematoxylin, BrdU-negative nuclei are blue. TUNEL assay of normal (C) and Tenm4m1(D) embryos at E7.5. Whole-mount immunostaining using an anti-Pou5f1 antibody in wildtype (E) and Tenm4m1/m1(F) embryos at E7.5. Teratomas derived from wildtype and Tenm4m1/m1embryos fail to differentiate in a cell autonomous manner. Histological sections of 7 week old teratoma derived from wildtype embryo (G-I), 7 week old teratoma derived from Tenm4m1/m1(J) and 1 week old teratoma derived from Tenm4m1/m1(K). Keratinized epithelium (ke) in wildtype teratoma (G). Undefined tissue, which may be cartilage (c) in wildtype teratoma (H). Endodermal tissue, which may be gut (g) in wildtype teratoma (I). Degenerated teratoma derived from Tenm4m1/m1(J and K). Inflammation with dead blood cells (*) indicating degradation of teratoma. Blood cells invading into teratoma (#). Bar 50 μm (A-D), 100μm (E-K).