Figure 3.

Whisker follicles develop by E18.5, but they are aberrant in GATA-3-null embryos. Whisker pads of E18.5 wild-type (WT) and GATA-3nlslacz(z/z) (GATA-3-null) embryos were frozen and sectioned (10 μm). Serial sections (denoted by i, ii, iii) of two wild-type follicles (A,B) and two KO follicles (C,D) are shown. Sections were either subjected to H&E staining (A–D) or triple indirect immunofluorescence microscopy using the antibodies indicated in the lower right of each frame. Color coding reflects the secondary Abs used for detection. Brackets in Ai and Bi denote a gap between the hair cortex (red, AE13) and companion cell layer (green, K6). This gap represents the IRS (red, AE15; Aii and Bii), which is sandwiched between the companion layer and the cortex of wild-type follicles. In KO follicles, AE15 staining is largely absent, and K6 and AE13 staining are adjacent to one another. Additional abnormalities in embryonic KO follicles include nodular thickenings in the vibrissae shafts (marked with an asterisk; C), irregular bulges in the ORS (e.g., double-headed arrow; D), and a shortened, bent follicle of enlarged diameter at the bulb. Images are shown at 20× magnification. Panels are composites of two or three microscopic fields. (E) Barrier function analyses. The ability of whole embryos to exclude blue dye was used to examine the epidermal barrier, normally acquired beginning at E17.5 and complete by E18.5. Note the complete penetration of blue dye in a representative GATA-3-null E17.5 embryo, in contrast to the comparably sized E17.5 wild-type embryo, which has the characteristic dorsal pattern of dye exclusion. By E18.5, both wild-type and null embryos have acquired barrier function based on this assay. Note, however, that whiskers have not protruded from the muzzle of the KO embryo, in contrast to the wild-type littermate.