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Fig. 3. Tissue disintegration due to ECM deficiency in E18.5
Foxf2-/- intestine. (A,B) Hematoxylin and Eosin
stained sections of colon from wild type (A) and Foxf2-/-
(B). The mutant has a distended distal colon and the mesodermal layers
separate from each other and from the epithelium (top in close-up) because of
poor cell adhesion. (C-K) Immunostaining with antisera against a
sheet forming collagen (type IV), a fibrillar collagen (type I) and SMA. Both
collagens are reduced throughout the length of the intestine (from duodenum to
rectum) in Foxf2-/-. The mutant intestinal wall (I) is
flimsy in appearance compared with the wild type (H), owing to lack of
collagen fibers. Both the small intestine (I) and colon (E; here from a
proximal, non-distended part) has a smaller diameter in the mutant than in
wild-type littermates (C,H). Foxf1-/+;
Foxf2-/+ (D; proximal colon) also has reduced amounts of
ECM components, but less extreme than in Foxf2-/-.
(L,M) Immunostaining with anti-SMA in wild type (L) and
Foxf1-/+; Foxf2-/+ (M) E18.5 small
intestine shows ectopic expression of SMA in intravillus mesenchyme of the
mutant. (N-Q) Cell-autonomous requirement for Foxf proteins for
collagen expression in intestinal fibroblasts. Primary fibroblasts were
prepared from E18.5 wild-type intestine and transfected with a plasmid
expressing GFP (N,O) or a dominant-negative Foxf protein fused to GFP (P,Q).
After 24 hours, cells were fixed and stained with an antiserum against
collagen I (red). Collagen staining is seen in cytoplasmic vesicles and fibers
between the cell and the glass substrate. In cells expressing the
dominant-negative Foxf protein, identified by their green nuclear
fluorescence, collagen staining is reduced dramatically. Blue, DAPI nuclear
staining.
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