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Fig. 2. Xrx1 inhibits neurogenesis. The effects of Xrx1 overexpression on (A) X-ngnr-1 (stage 12), (B,D,E) X-Delta-1 (stage 13), (C) N-tubulin (stage 16), (F) Sox2 (stage 13) and (G) XBF-1 (stage 13) are shown. (D,E) Transverse sections at the level of the anterior (D) and posterior (E) neural plate. The black arrowhead indicates the anterior expression domain of X-Delta-1, while the white arrowhead indicates the repression of the corresponding domain in the injected side. (H) Stage 16 embryo injected with 150 pg of XBF-1 RNA showing suppression of endogenous N-tubulin (white arrowheads) as well as ectopic N-tubulin activation at the border of the injected area (arrow). A-C,F,G,H Frontodorsal views. (I,K) Stage 16 embryos co-injected with either X-ngnr-1 and lacZ (I) or X-ngnr-1, Xrx1 and lacZ (K); lateral views, anterior towards the left. (J,L) Animal caps co-injected with either X-ngnr-1 and lacZ (J) or X-ngnr-1 and Xrx1 (L) analyzed at stage 16. Both in whole embryos and in animal caps Xrx1 inhibits N-tubulin expression induced by X-ngnr-1. Red staining represents expression of co-injected lacZ lineage tracer. |
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Fig. 5. Xrx1 regulates the expression of genes that control cell proliferation and differentiation, and does not work through the Notch-Delta pathway at early neurula. (A-C,G,H,M) Comparison of the expression of Xrx1 to that of Zic2 (A,B), Xhairy2 (C), Xhairy1 (G), p27Xic1 (H) and X-Notch-1 (M) in stage 13 embryos. (D-F,I-L,N) Xrx1-injected embryos analyzed at stage 14 (D-F,J,K,N) or stage 18 (I,L). The probes used and the respective staining are indicated, color-coded, on the bottom of each panel. (A-D,F-O) Frontal views, dorsal towards the top; (E,P,Q) dorsoanterior views. The injected side of the embryos (to the right of vertical bars representing the midline) is indicated (inj). Red staining in F,I,J,K,L,N-Q and turquoise staining in D,E represent expression of co-injected lacZ lineage tracer. (F,J,K) Black arrowheads indicate the lateroventral expression domain of Xhairy2 (F), Xhairy1 (J) and p27Xic1 (K) in the uninjected control side of the embryos. White arrowheads indicate the corresponding expression domain in the injected side, which is expanded in the case of Xhairy2 (F) and repressed in the case of Xhairy1 (J) and p27Xic1 (K). Black brackets indicate the anterior expression domains of Zic2 (D,E), cyclinD1 (I) and Xoptx2 (L) in the control uninjected side; white brackets indicate the corresponding enlarged domains in the injected side. (O) Stage 14 embryo injected with Notch-ICD showing no significant change in Xrx1 expression. (P,Q) Stage 16 embryos injected with X-Delta-1stu and lacZ (P) or co-injected with Xrx1, X-Delta-1stu and lacZ (Q). Xrx1 represses N-tubulin expression in the trigeminal ganglion but does not affect N-tubulin posterior expansion. Arrows indicate the increase in density of N-tubulin-positive cells within the posterior neurogenic stripes caused by the block of lateral inhibition. The black arrowhead indicates N-tubulin expression in the trigeminal ganglion of the uninjected side; the white arrowhead indicates the absence of this expression domain in the injected side. |
