Fig. 2

Fig. 2

The zebrafish 2P element drives lacZ reporter expression in the ectodermal cells only of the mouse fore- and hindlimb buds. (A, B, E-J) E11.5, (C, D, K-P) E13.5 Tg(2Pand1::LacZ) transgenic mouse embryos. Fore- (B, E-G, K-M) and hindlimb (D, H-J, N-P) buds are presented for E11.5 and E13.5. Ventral close up of forelimb at E11.5 (B) and E13.5 (D). Limbs were sectioned along the proximal distal axis indicated by the black line (B, D). Note the presence of reporter expression in the ectodermal cells only. Note both limbs show an absence of expression in the AER at E11.5 (indicated by the yellow arrowheads) (E-G, H-J). In contrast, at E13.5, lacZ expression is present in the entire distal ectoderm of the forelimb bud (K-M), visualizing AER regression. Cross sections of fore- (F-G, L-M) and hindlimb (I-J, O-P) bud reveal an absence of reporter expression in the mesenchymal tissues at all stages. Note: Brain expression (A, C) is limited to this transgenic line, and is likely ectopic due to the transgene insertion site. AER, Apical Ectodermal Ridge, Mes, Mesenchyme. Scale bars: 1000 µm in A, D; 320µm in B, D; 200 µm in E, H; 400 µm in K; 500 µm in N; 100 µm in F, I; 30 µm in G, J; 100 µm in L; 60 µm in O; 50 µm in M; 30 µm in P.