Figure 1.

(A) Expression of anteroposterior neural marker genes in combined animal caps expressing activated Xlim-1/3m and Xbra. An animal cap from a embryo injected with mRNAs (cap 1) in the indicated amounts (ng/embryo) was combined with another cap (cap 2) as indicated. Two experiments of identical design, identified as I and II, are presented in one panel. Six combined caps were collected at equivalent stage 22/23 (blot I) or 27/28 (blot II), and the RNA was assayed by Northern blot analysis. NCAM is a pan-neural marker, and XCG7 identifies the cement gland, an anterior ectodermal derivative; the following neural markers from Otx2 through HoxB9 are arranged in anteroposterior order of their expression. (B) Xbra-induced posteriorization of neural tissue generated by noggin and chordin. The injected RNAs are indicated above the blot; 3mHDm is a homeodomain mutant derivative of Xlim-1/3m that is expected to be inactive and is used as control, as is globin mRNA.