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Fig. 2. Tbx2b is required for cells to adopt a neural fate. Deep cells from embryos
co-injected with fluorescein-dextran (70 kDa) and tbx2b MO at 30%
epiboly were transplanted into homochronic wild-type hosts. (A) Cross-section
through the neuroretina and brain shows transplanted control labelled cells in
the CNS. By contrast (B) transplanted Tbx2b-deficient cells were present only
in the epidermis (arrowheads). (C) One central blastomere of 16-cell stage
embryos was injected with fluorescein either with or without tbx2b
MO, and embryos were allowed to develop to 24 hpf. Both control and
tbx2b morphants developed normally and showed a similar distribution
of labelled clones in vivo at 3.25 hours. (D) Dorsal view of 24 hpf control
embryo shows labelled cells in neural plate and epidermis. (E) tbx2b
morphant labelled cells were present only in epidermis. (F,G) Whole-mount in
situ hybridization with the pan-neural marker sox19 shows a delay in
convergence of the neural plate in tbx2b morphant (arrow in G)
compared with control (F). (H-K) Whole-mount in situ hybridization with
bmp2 (H,I) and fz7 (J,K) show similar expression patterns in
control and Tbx2b morphant at 5 hpf. (L-N) Transplanted fluorescein labelled
Tbx2b-deficient cells continue to express sox19 in 5 hpf wild-type
host. (N) The merged photographs were enhanced in Adobe Photoshop such that
only the simultaneous presence of blue (whole-mount in situ hybridization
signal) and green (fluorescence) produced a purple signature. Otherwise, cells
remain grey.
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