Fig. 1. Hfp negatively regulates cell cycle progression. (A) A wild-type third instar larva (left) alongside an hfp^EP/hfp^EP late third instar larva (right). (B) A wild-type pharate adult (left) alongside a hfp^EP/hfp^EP pharate adult (terminal phenotype; right). (C) Time line of the developmental delay observed in hfp^EP/hfp^EP animals compared with wild type. The vertical bar indicates the stage at which hfp mutants arrest in development and die. (D) Northern blot of poly(A)+ RNA isolated from the developmental stages shown, and probed with the hfp cDNA, then stripped and re-probed with the ribosomal protein rp49 cDNA as a loading control. (E) Northern blot of poly(A)+ RNA isolated from wild-type and hfp mutant larvae, probed with the hfp cDNA and Actin5c cDNA as a loading control. (F-N) Wing imaginal discs from wandering third instar larvae. Posterior is to the right, and the left margin of the ZNC is marked with a yellow bar. Discs shown are representative samples of at least 30 discs examined for each condition. (F,G) Wild type disc co-stained with anti-Geminin antibody (F) and anti-Hfp antibody (G). Geminin is present in late S-phase and G2 cells, but absent from G1-arrested cells (Quinn et al., 2001). (H) Anti-Hfp antibody staining of a hfp^EP/hfp^EP larval wing disc. (I-N) Wing discs from wild type (I-K) and hfp^EP/hfp^EP (L-N) larvae co-labelled with BrdU (I,L), anti-phosphohistone H3 antibody (PH3) (J,M) or merged (K,N). (O-T) Third instar eye imaginal discs from wild-type (O-Q) and hfp^EP/hfp^EP (R-T) larvae co-labelled with BrdU (O,R), PH3 (P,S) or merged (Q,T). The morphogenetic furrow (MF) is indicated by a yellow bar and arrows indicate the normal position of the S-phase band posterior to the MF. (U,V) Cell size visualized by spectrin staining of wild type (U) and hfp^EP/hfp^EP (V) wing discs. (W,X) TUNEL staining of wild-type (W) and hfp^EP/hfp^EP (X) wing discs, revealing elevated apoptosis in hfp mutant tissue.