Tramtrack, downstream of Notch, is involved in cell cycle regulation but not in cell differentiation. (A, A') Notch is processed and cleared normally from the apical side of follicle cells in ttk-clones. (B, B') Cut down-regulation is normal in ttk-clones (23/23, except in the most posterior region, Supp Fig. 1; Althauser et al., 2005). N mutant clones (C, C') but not ttk mutant clones (D, D') show ectopic expression of FAS3 after the transition, indicating that Ttk does not act in Notch dependent follicle cell differentiation that involves Fas3. (E, E') N mutant clones (stage 9 egg chamber) show reduction of ttk expression (red), indicating that Ttk is downstream of N. However, this result does not rule out the possibility that Ttk acts in a parallel pathway. All cells are marked with DAPI (blue), GFP is green, clones are marked with dashed lines.
Jordan et al. BMC Developmental Biology 2006 6:16 doi:10.1186/1471-213X-6-16