Endogenous matrix or BME rescues the orientation of polarization but not single lumen formation.

<p><b>A–F</b>: Cells expressing CA-Pak1 (A,B) or CA-Pak1ΔPIX (C,D) were grown in BME for four days before staining for PCX (green in A–D), β-catenin (red in A–D) and nuclei (blue in A–D). Scale bars are 10 µm. <b>E–F</b>: Quantification of apical orientation (F) and lumen formation (G) of cysts shown in A–D. Data show means ± SEM. n = 3.