| |
Fig. 3. BMPpathway overactivation affects cell specification in the developing Xenopus epidermis. Stage 9 Xenopus embryos were injected in the blastocoel
with either BSA (A-M) or 2-7 ng recombinant BMP4 (A′-M′). (A,A′) SEM of the epidermis at stage 37 revealed the severe decrease in the numbers of MCCs
(red arrowhead), ionocytes (yellow arrowhead) and SSCs (green arrowhead). (B,B′) At tailbud (stage 30), BMP4-injected embryos showed normal morphology but
substantially fewer α-tubulin-positive MCCs, as revealed by whole-mount in situ hybridisation (WISH). (C,C′) Both the differentiated MCC marker acetylated tubulin
(white) and the ionocytemarker foxi1e (green)were lost in sectioned tailbud (stage 25)BMP4-injected embryos. (D,D′)WISHrevealed that the differentiated ionocyte
marker v1awas strongly decreased in stage 25BMP4-injectedembryos. (E-F′) The differentiatedSSCsmarkers serotonin (red in E,E′) andtryptophan hydroxylase-1
(tph1, red in F,F′)were lost or strongly decreased in stage 25BMP4-injected embryos. (G,G′) In sections of stage 25BMP4-injected embryos, P63 (white), amarker of
the non-intercalatinginner layercells,was lost,whereasthe goblet cellmarker intelectin-1 (green)wasupregulated. otogelin (redin H,H′,J,J′)andtrim29(red in I,I′), two
other markers of goblet cells, were unaffected. (K-M′) Stage 14 embryos were analysed by WISH in order to stain MCCs for foxj1 (K,K′), ionocytes for foxi1e (L,L′)
and SSCs for foxa1 (M,M′). (B,B′,D-F′,J-M′) Whole-mount embryos; (C,C′,G-I′) cryosectioned embryos. (B-M′) All markers were revealed by chromogenic or
fluorescent in situ hybridisation, except for acetylated tubulin, serotonin and P63, which were revealed by immunofluorescence. (C,C′,E-I′) Nuclei were stained with
DAPI. (B,B′,D-F′,K-M′) The number of embryos showing the phenotype among the total number of embryos examined is indicated. |
| |
Fig. 6. BMP inhibition prevents the intercalation of MCCs, ionocytes and SSCs in the outer layer of the developing Xenopus epidermis. (A-E′) Sectioning
through the epidermis at stage 25 revealed that in the BMP MO-injected embryos the supernumerary α-tubulin-positive MCCs (red in A-C′) and v1a-positive
ionocytes (red in D-E′) fail to intercalate into the epidermis outer layer. (I-J′) Likewise, the supernumerary tph1-positive SSCs failed to intercalate in stage 35 BMP
morphants (red in I-J′). (F-H′,K-M′) Even at later developmental stages, most of the supernumerary MCCs, which expressed the differentiation marker acetylated
tubulin (white), were unable to intercalate properly into the outer layer. |
