Fig. 7. Early defects in kidney development in mice constitutively lacking plexin B1 expression (Plxnb1^-/-). (A) When compared with heterozygous control littermates (Plxnb1^+/-), Plxnb1^-/- mice show a loss of plexin B1 mRNA, whereas the expression of plexin-B2 mRNA remains unchanged. (B,C) Typical examples of kidneys dissected out of Plxnb1^-/- (B) and Plxnb1^+/- (C) littermates at E13.5 and stained with an anti-calbindin-28K antibody. (D-G) In comparison with heterozygous littermates, Plxnb1^-/- kidneys are larger in size (D,E) and have increased ureteric branching (F,G) at E13.5. (H,I) At E14.5, Plxnb1^-/- mice show a larger area of kidneys than heterozygous littermates, but at E15.5 no differences can be detected. (J) The number of developed nephrons is not significantly different between Plxnb1^-/- and Plxnb1^+/- littermates at E17.5. ^*P<0.001, Student's t-test. Scale bar: 200 µm.