Transition in epithelial follicle cells from mitotic cycle to endocycle during Drosophila oogenesis. (A) Signaling from the Notch pathway causes follicle cells surrounding each oocyte to cease mitosis and begin endocycling at stage 6–7. (B) Cyclin A, (C) Cyclin B and (A) PH3 expression through stage 6 indicates the mitotically active follicle cells. (D) Notch protein is also expressed on the apical side of the follicle cells through stage 6 (arrow) and is cleared from the plasma-membrane upon activation. (E) String (stg), as shown by stg-lacZ (6.4 kb) promoter construct and (F) dacapo (dap), as shown by dap-5gm promoter construct, are both expressed in follicle cells prior to the transition and down-regulated in response to Notch signaling. (G) Fizzy-related (fzr), as shown by Fzr-lacZ enhancer trap line fzrG0326, is expressed in follicle cells after the transition. (H and H') Phosphorylated JNK staining (green) is upregulated in the follicle cells prior to the mitotic-to-endocycle transition in WT egg chambers. All cells are labeled by DAPI (red). (I and I') Puc-LacZ (green), a reporter construct for Puckered (pucA251), expression is upregulated in follicle cells during mitosis. All cells are marked with DAPI (red).
Jordan et al. BMC Developmental Biology 2006 6:16 doi:10.1186/1471-213X-6-16