Fig. 5.

Axin mutant proteins with mutated contact residues nevertheless retain significant functional activity in vivo. The mutations in the Armadillo binding site, L501P and H504L resemble in phenotype the loss for the binding site (AxinΔArm). Similarly, L447S and L447Q produce a similar phenotype as AxinΔSgg, whereas AxinK446E resembles wild type. axin^null embryos expressing maternally deposited tub>Axin* mutant protein were scored for their ability to restore the segmentally repeated cuticle pattern of abdominal denticle belts, consisting of six rows of denticles (A,A′, arrow) alternating with smooth cuticle (arrowhead). Cuticle scoring criteria: The abdominal region, consisting of 8 denticle belts and 7 bands of smooth cuticle, was scored on 1–10 scale. Embryos were scored as follows: 1=loss of 7–8 denticle belts (=axin phenotype); 2=loss of 4–7 denticle belts; 3=loss of 1–3 denticle belts; 4=no loss of denticle belts, but minor loss of denticle within the belts; 5=wild type; 6=the presence of some ectopic denticles in smooth cuticle bands; 7=loss of 1–2 smooth cuticle bands; 8=loss of 3–4 smooth cuticle bands; 9=loss of 5–6 smooth bands; 10=no smooth cuticle (wingless phenotype). Bands were scored as missing if more than 50% of the denticle band was deleted. Phenotypic scores are indicated in the lower right corner of the dark field image.

(A) Wild type (wt). (B, B′) Embryos expressing AxinΔArm showed modest loss of denticles, including a frequent loss of row 1 denticles (brackets in panel B′), loss of posterior denticles (arrowhead) and replacement of part of the belt by smooth cuticle. (C) Embryo expressing AxinL501P displays loss of part of a denticle belt (arrows in C′). (H) An AxinH504L expressing embryo is lacking some row1 denticles (bracket in D′). (E) Embryos expressing AxinΔSgg cuticles showed a marked loss of denticles. (E′) A magnified ventral view of another embryo, showing significant portions of the abdominal belts did not form (arrows). (F) An embryo expressing AxinK446E appears nearly wild type except for the occasional loss of row 1 denticles (bracket in F′). (G) AxinL447S expressing embryo, which displays a marked loss of denticles (arrows in G′). (H) Similar to AxinΔSgg and AxinL447S, embryos expressing AxinL447Q also lack significant parts of denticle bands (arrows in H′). Bar=100 μm in panels A H; 25 μm in panels A′–H′.