δ-EF1 is a negative regulator ofIhhin the developing growth plate

(A-B”) Alizarin Red/Alcian Blue staining of forelimbs of WT and δEF1-/- mice at 14.5 dpc (A,B), 16.5 dpc (A’,B’) and 18.5 dpc (A”,B”). (C-D”) Safranin O staining of humerus of WT and δEF1-/- mice at 14.5 dpc (C-D), 16.5 dpc (C’-D’) and 18.5 dpc (C”-D”). Scale bar, 500µm. The yellow, blue and green rectangles correspond to proliferating, prehypertrophic and hypertrophic zones of the growth plate and are magnified in E-J”. Scale bar, 100µm. The arrowheads in G’-H’ indicate perturbed column formation of prehypertrophic chondrocytes in δEF1 null mice as compared to WT mice. The brackets in G”-H” indicate columnar stacks. The black and yellow lines in I’-J” indicate the size of the hypertrophic zone in WT and δEF1 null mice respectively. Note disturbed columnar organization as well as the reduced size of prehypertrophic and hypertrophic zones in δEF1 null mice. (K-K”) Measurements of the different cartilage zones in WT (black bars) and δEF1 null mice (grey bars) (n= 4 embryos, 5 measurements per embryo in each group, mean ±SD, Student’s T-test *p<0,0001).