|
Display additional annotations [+]
|
| |
Fig. 2. Expression of milk by in situ hybridisation on whole and sectioned embryos. milk-mRNA is first detected by whole-mount in situ hybridisation following the mid-blastula transition in the marginal zone (A-D). (A) Embryo at the late blastula stage (stage 9), vegetal view, dorsal is up; (B) mid-gastrula stage (stage 11), vegetal view, dorsal is up. (C) The same embryo as in A, lateral view, dorsal is to the right. Note that milk seems to be more highly expressed in the dorsal part. (D) The same embryo as in B, lateral view, dorsal is to the right. At this stage, the dorsoventral gradient appears less pronounced. At late stage gastrula and later stages in development, milk mRNA is no longer detectable (not shown). On sectioned embryos (E-I) milk is expressed in mesendoderm at the early gastrula stage and becomes restricted to the endoderm during gastrulation. (E,F,G) Hybridisation with respectively Xbra, milk and Mix.1, on alternate sections of the same embryo at stage 10.25. Note that the expression patterns of milk and Mix.1 largely overlap that of the mesodermal marker Xbra. (H,I) Hybridisation with respectively Xbra and milk on alternate sections of an albino embryo at stage 11.5. Note that milk mRNA is excluded from the involuting mesoderm (chordomesoderm and caudal mesoderm) whereas Xbra mRNA is clearly visible. The sections in H and I were imaged under the same contrast and brightness settings and printed as negative images to reinforce contrast differences between specific and background stainings. In all panels, dorsal is to the right. Arrowhead indicates the dorsal blastoporal lip. |
|
Display additional annotations [+]
|
| |
Fig. 5. Effect of milk injection on Xbra, goosecoid, Xvent-1 and endodermin expression. Overexpression of milk in the dorsal marginal zone results in down-regulation of the early mesodermal markers Xbra and gsc and in the stimulation of edd expression revealed by in situ hybridisation. (A) Xbra expression in an uninjected embryo at stage 11.5. (B) Xbra expression in an embryo injected dorsally with 100 pg of milk plus lacζ mRNA. The cells stained with X-gal do not express Xbra. (C) gsc expression in an uninjected embryo at stage 10.25. (D) gsc expression in an embryo injected dorsally with 100 pg of milk plus lacζ mRNA. The cells stained with X-gal do not express gsc similar to that seen with Xbra. (E) Xvent-1 expression in an uninjected embryo at stage 11.5. (F) Xvent-1 expression in an embryo injected ventrally with 100 pg of milk RNA. Note a repression of Xvent-1 hybridisation signal on the site of milk injection. (G) Embryo coinjected with 100 pg of milk plus lacζ mRNA then stained with X- gal at stage 11.5. (H) The same embryos as in G labelled by an edd- digoxigenin riboprobe. The X-gal-positive cells express edd. edd expression expands outside its normal expression domain (see control J). (I) Embryo injected with 500 pg of milk plus lacζ into one micromere at the 8-cell stage, then stained with X-gal prior to in situ hybridisation for edd at stage 12. Note a patch of edd-expressing cells within the domain of X-gal-positive cells. (J) edd expression in an uninjected embryo at stage 11.5. |
