Fig. 4. Cell proliferation in the developing eyelid epithelium in wild-type and Fgf10^–/– mice. (A-C) BrdU analysis of the E11.5 eyelid. (A,B) Histological sections for BrdU staining. The red line underlies the epithelium where the number of BrdU-positive cells was counted (see Materials and methods for details). (C) The total number of proliferating cells from three sections was processed for quantitative histomorphometry. Compared to wild-type animals, the proliferation in Fgf10^–/– mutant epithelia was significantly reduced. BrdU incorporation was particularly noticeable in the wild-type eyelid groove, as shown in A. (D-H) BrdU analysis of the E13.5 eyelid. (D-G) Histological sections for BrdU staining. The upper and lower eyelids are at the left and right, respectively. The proliferation rates were significantly reduced in the Fgf10^–/– mutants. BrdU incorporation was particularly noticeable in the apex region of the wild-type eyelid, as shown in F. (I-M) BrdU analysis of the E15 eyelid. (I-L) Histological sections for BrdU staining. At E15, the Fgf10-null upper and lower eyelid epithelia showed no significant decrease in proliferation. In C, H and M the y axes indicate the cell number or mean percentage of BrdU incorporation in each area assayed. The error bars represent the s.e.m.; an asterisk denotes a significant finding (P<0.05), as compared with the wild-type value. In D,E,I,J, the dotted lines indicate the length of epithelium measured. Scale bars: 25 µm (A,B); 100 µm (D,E); 50 µm (F,G); 100 µm (I,J); 50 µm (K,L).