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Fig. 6. GATA5 respecifies prospective mesoderm towards endoderm. Whole-mount in situ hybridisations of control embryos (A-C top row, D-G,L) or GATA5 injected embryos (A-C bottom row, H-K, M) at stage 11 (A-C) or the stages indicated (D-M) using the indicated probes. Embryos were injected with either 50 pg GATA2a or 50 pg GATA5 RNA per blastomere as indicated in the figure and described in the text. Expression of Xbra (A) and chordin (B) is reduced in GATA5 injected embryos (arrows), while Sox17α is ectopically induced
(C, arrows). Embryos injected at the four-cell stage into two dorsal blastomeres with RNA coding for nuclear β-galactosidase on its own (D-G) or coinjected with 50 pg GATA5 RNA (H-K) were stained for β- galactosidase at the indicated stages. Dorsal injection of GATA5 disrupts convergence and extension movements. The dorsal blastopore is marked by arrowheads, axial mesoderm by arrows and anterior mesendoderm by asterisks. (L,M) Whole mount in situ hybridisations of β-galactosidase stained embryos in E and I, respectively, with a Sox17α specific probe. (N,O) Vibratome cross sections of stage 12 embryos shown in L and M, respectively. In control embryos the majority of lacZ-positive cells (turquoise) do not express Sox17α (purple), while in GATA5-injected embryos lacZ-positive cells also express Sox17α (arrows in O; cytoplasm as well as nuclei now blue). Arrowheads mark the dorsal blastopore lip and the arrows in L,N indicate the Sox17α positive dorsoanterior endoderm. Embryos in A-E,H-J are viewed from the vegetal pole. Anterior is towards the left in the other whole mount panels. |
