Fig. 3. Colocalization of PTEN2 and Baz in embryonic epithelia and neuroblasts is dependent on the PDZ-binding motif of PTEN2. (A) An embryo expressing PTEN2 ubiquitously under control of a maternal GAL4 driver was stained with antibodies against PTEN and Baz. Both proteins colocalize in the apical cortex of the epidermis (arrows) and in the apical cortex of neuroblasts (asterisks). (B) At later developmental stages, apical colocalization of PTEN2 and Baz in epithelia is even more pronounced. Neurotactin (blue, right panel) was used as a marker for the basolateral membrane. No overlap between PTEN and Neurotactin is visible. (C) The PTEN3 isoform, which lacks the PDZ-binding motif at the C terminus but is otherwise identical to PTEN2 is localized on the whole plasma membrane and in the cytoplasm. PTEN3 staining clearly overlaps with Neurotactin on the basolateral membrane (purple, right panel). Apical localization of Baz is unaffected by overexpression of PTEN3. (D) PtdIns(4,5)P₂ colocalizes with Baz in the embryonic epidermis. We expressed a PLC-PH-GFP fusion protein under control of a ubiquitous maternal promoter and stained these embryos with an antibody against Baz. The PLC-PH-GFP fusion protein is present on the whole plasma membrane except for the free apical surface and is strongly enriched in the most apical region of the lateral plasma membrane where it colocalizes with Baz. The embryos shown are at stage 10 (A) and at stage 13 (B-D) (Campos-Ortega and Hartenstein, 1997). Genotypes are: P{w ^+mC=matalpha4-GAL-VP16}V67;UAS Pten2 (A); P{w ^+mC=Act5C-GAL4}17bF01;UAS Pten2 (B); P{w ^+mC=Act5C-GAL4}17bF01/UAS Pten3 (C); and P{w ^+mC=matalpha4-GAL-VP16}V67/UAS PLC-PH-GFP (D). Scale bar: 20 µm.