Fig. 3. Analysis of cartilage development in C4st1^gt/gt embryos by staining for lacZ. Part i, wild type; part ii, mutant. (A,D) Identical staining in whole-mount (A) and sectioned (D) forelimb buds of cartilage aggregations (arrows) in +/gt (i) and gt/gt (ii) E11.5 embryos. Asterisk indicates AER. (B,E) Whole-mount staining of cartilage primordia (B) and sectioning of stained tibia primordium (E) at E13.5 in +/gt (i) and gt/gt (ii) hindlimbs shows no differences in size of cartilage elements or cellular patterning. Abbreviations in B: d, digits; t, tibia; fi, fibula; f, femur. Abbreviations in E: d, distal; p, proximal. Arrowhead indicates slight bending of gt/gt tibia primordium. (C) Whole-mount staining of hindlimbs at E15.5, showing impaired segmentation of cartilage in digits (arrowhead) and bending of tibia (arrow) in gt/gt (ii), but not +/gt (i) embryos. d, digits; t, tibia; fi, fibula. (F) Sectioned proximal tibia of stained +/gt (i) and gt/gt (ii) E15.5 hindlimbs. Homozygous mutant growth plates are slightly shortened (double-headed arrow) and show a decrease in the size of the columnar zone (c). p, proliferative zone; h, hypertrophic zone. Scale bar: 100 µm for A,D; 300 µm for B; 100 µm for E; 600 µm for C; 200 µm for F.