(A–D). Expression patterns of Bcd (A), Kr (B), Run (C), and Cic (D) in early NC14 embryos. Boxes represent regions used for quantification. (E). Average expression profiles of Bcd (n=8), Kr (n=6), Run (n=8) and Cic (n=8). (F). Model of gene expression boundary registration in the anterior half of the embryo. The Cic repression gradient is established via Tor down-regulation of Cic at the anterior tip. Bcd activates slp1 and gt, which encode repressors that set the anterior boundaries of run and Kr transcription. The Cic, Run, and Kr gradients repress Bcd-dependent activation of target genes, including slp1 and gt themselves.