Fig. 4. Abnormal epiblast polarity and disruption of endodermal tight junctions in PINCH1-null EBs. (A,B) In normal EBs the cis-Golgi matrix protein GM130 (red) is localized to the apical region of the epiblast and to the basolateral region of the endoderm. GM130 is also observed in the apical side of the remaining ICM cells facing the cavity. In PINCH1-null EBs, GM130 is peri-nuclear in the endoderm, and sometimes apical in the epiblast although in a non-linear fashion (B). Arrowheads showing a large segment of endoderm detached from the basement membrane. (C,D) E-cadherin is localized to the lateral plasma membrane and concentrated at the apex of the epiblast (C). PINCH1-null EBs show reduced apical E-cadherin signals in the epiblast and often miss segments of endodermal cells (asterisk; D). (E,F) ZO-1 is found in the apex of the cell-cell junctions of normal endoderm (E, arrowheads). In PINCH1-null endoderm, ZO-1 is found at the basal or entire apical and lateral plasma membranes (F, arrowhead).