Fig. 4. Pten mutant embryos fail to localize germ plasm determinants and do not form pole cells. (A) In freshly laid wild-type eggs, oskar mRNA is strongly enriched at the posterior pole. (B,C) in eggs derived from Pten germline clones, oskar mRNA is detectable at the posterior pole only at a low level (B) or not at all (C). (D,D') In wild-type embryos at nuclear division cycle 6 (64 nuclei), the nuclei have spread into an ellipsoid cloud in the yolk (dashed ellipse) and the germ plasm component Vasa is enriched at the posterior pole (arrowhead). (E,E') In Pten mutant embryos derived from germ-line clones at nuclear division cycle 6 the nuclei stay together in an almost circular cloud (broken circle) and Vasa is only slightly enriched at the posterior pole. (F,F') Vasa staining is restricted to pole cells (arrowhead) in wild-type embryos at late syncytial blastoderm stage. (G,G') In Pten mutants, pole cells do not form and Vasa staining is absent from the posterior pole (arrowhead). Arrows indicate borders between nuclei in different stages of the cell cycle. (H,H') In a wild-type embryo at the extended germ band stage, Vasa staining is restricted to germ cells (arrowhead). (I,I') In a Pten mutant embryo derived from a germ-line clone, germ cells are absent and no Vasa staining can be detected (arrowheads indicate the position where germ cells are found in wild type). DNA was stained with YOYO-1. In all images, anterior is towards the left. Scale bar: 100 µm.