Figure 4

Induction of G1 arrest by activated Thickvein. The activated receptor Tkv^QD was expressed in clones also expressing GFP (green). Cell cycle activity was monitored through labeling for CycB (red) and phospho-H3 (blue). These two markers gave consistent results. 50 Tkv^QD-expressing pH3-labelled cells in thirteen clones were CycB positive, while 17 pH3-labelled cells in anaphase/telophase were Cyclin B negative, reflecting the metaphase proteolysis of Cyclin B. (A) Near the morphogenetic furrow, close to where wild type cells arrest in G1, Tkv^QD accelerates arrest of all cells; (B) Higher magnification and separate channels; (C) Clones expressing Tkv^QD at more anterior locations continued proliferating before arresting about twice as far from the morphogenetic furrow as wild type cells, so that each clone had an anterior, proliferating segment and a posterior, arrested segment; (D) Higher magnification and separated channels; (E) Clone located more anteriorly than that in panel C; (F) higher magnification and separated channels; (G) In the most anterior parts of the eye disc, Tkv^QDexpression was not sufficient to cause cell cycle arrest; (H) higher magnification and separated channels.