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Fig. 5. BMP inhibition promotes MCC, ionocyte and SSC fates in the developing Xenopus epidermis. (A-O′) Eight-cell stage Xenopus embryos were
injected in one animal ventral blastomere (fated to become only epidermis) with either 500 pg GFP mRNA alone (Cntl) or with 500 pg GFP mRNA and BMP2,
BMP4 and BMP7 morpholinos (BMP MOs, 10 ng each) and were analysed at stage 14 (A-F′) or 25 (G-O′). GFP immunostaining was used to identify the injected
cells. Injection of BMP MOs resulted in an increase in the numbers of stage 14 inner layer cells expressing markers for committed MCCs ( foxj1 and MCI, red in A,A′
and B,B′, respectively), for committed ionocytes ( foxi1e, red in C,C′) and for committed SSCs ( foxa1, red in D,D′). Conversely, injection of BMP MOs led to a
severe decrease in the expression levels of the goblet cell markers otogelin and trim29 (red in E,E′ and F,F′, respectively). When analysed at stage 25, embryos
injected with BMP MOs showed an increase in the numbers of both α-tubulin-positive MCCs (white in G,G′,I,I′) and foxi1e-positive ionocytes (red in H,H′,I,I′),
together with a decrease in the expression levels of the outer layer goblet cell markers intelectin-1 (red in J,J′.L,L′) and 5G7 (white in K-L′) and of the inner layer
non-intercalating cell markers P63 (white in M,M′,O,O′) and α-dystroglycan (red in N,N′,O,O′). (A-F′,M-O′) Cryosectioned embryos; (G-L′) Whole-mount
embryos. (P-S) Quantification of the different inner layer cellular populations in injected epidermal clones at stage 25. Shown are the percentages of MCCs (P),
ionocytes (Q), SSCs (R) and P63-positive inner non-intercalating cells (S) among injected, GFP-positive cells. The increase in the number of MCCs, ionocytes
and SSCs in BMP morphants was significant (Student’s t-test). No significant variation was observed for P63-positive cells. Error bars indicate s.d. |
