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Fig. 1. Expression of Mi-2ß mRNA during epidermal development and
conditional inactivation of Mi-2ß in the skin. (A) In
situ hybridization studies reveal Mi-2ß mRNA expression at E10.5, E14.5,
E18.5 and P1. Mi-2ß is uniformly expressed in the embryonic ectoderm
(E10.5). Mi-2ß transcripts are also detected in E14.5 epidermis in the
basal and stratum intermediate layers. In the differentiating hair follicle,
increased levels of Mi-2ß mRNA are first detected in the placode
(arrowhead) and then in the matrix (arrow). Scale bar: 50 µm. (B)
Cre-dependent conversion of the floxed allele (LoxPF) to the mutant allele
(
F) in the P1 dorsal epidermis revealed by PCR of genomic DNA (lanes 2
and 4). (C) Wild-type (WT) and mutant littermates at P1. (D)
Hematoxylin and Eosin-stained cross-sections of WT and mutant skin at P1. The
dotted line demarcates the dorsal region and the unbroken line the ventral
region. The mutant skin exhibits an exacerbation of phenotypes from the dorsal
to the ventral side that includes thinning of the epidermis and reduction in
hair follicles. Scale bar: 100 µm. A further magnification of the mutant
skin is provided beneath to show the absence of the basal layer and the
thinning of the suprabasal and cornified layers in the ventral region (right),
and the more normal epidermal differentiation in the dorsal region (left).
(E) The presence of Mi-2ß protein (green) in WT (left) and in the
dorsal (middle) and ventral (right) mutant skin was evaluated by
immunofluoresence at successive stages of development. DAPI-stained nuclei are
shown in red, and the white dotted line demarcates the dermal-epidermal
junction. Expression of Mi-2ß protein is indicated by the presence of
yellow nuclei, depletion of Mi-2ß by red nuclei. Depletion of Mi-2ß
protein occurs earlier (E10.5) in the ventral skin, and later (E13.5 and
later) in the dorsal skin. Scale bar: 50 µm.
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