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Fig. 2. Developmental RhoV mRNA expression. In situ hybridization of stages 10.5 and 11 (A, B) (vegetal views, dorsal towards the top). At the onset of gastrulation, RhoV is expressed in the dorsal marginal zone. Xbra expression at stage 11 is shown for comparison (C, vegetal view, dorsal towards the top). Shown in panels B′ and C′ are sagittal hemisections across the transverse lines in panels B and C, respectively (dorsal side on the right). At mid-gastrula stages, RhoV and Xbra stainings are detected in the involuting dorsal mesodermal cells (idm). At the end of gastrulation (stages 12 and 12.5, D–G), RhoV mRNA localizes at the dorsal side of the embryo above the blastopore (bl). From stage 12, a second domain of expression is detected at the lateral edges of the neural plate (black arrowheads), as compared with Snail-positive neural crest territory (H, black arrowheads). Shown are vegetal views of stage 12 (D) and stage 12.5 (E), dorsal views of stage 12.5 (F–H). RhoV/Snail (I and J) and RhoV/Sox9 (L and M) double in situ hybridization analyses. Shown in panels J and M are magnified views of the area boxed respectively in panels I and L. (K) Single Sox9 in situ hybridization is shown for comparison. At early neurula stages (13–14) (N, P), RhoV mRNA appears as an arc surrounding the entire neural plate border, covering both the lateral (black arrowheads) and the anterior (white arrowhead) neural plate border as observed for Snail (O). At stage 15, RhoV (Q) like Snail (R) is expressed in the anterior (white arrowhead) neural plate border and in the medial (red arrowhead) and lateral (black arrow) neural crests. Shown in panels Q′ and R′ are sagittal hemisections across the transverse lines in panels Q and R. (S) RhoV/Snail double in situ hybridization analysis. Like Snail, RhoV is expressed in the medial (red arrowhead) and lateral (black arrow) neural crests. (T) Control Sox9 in situ hybridization is shown for comparison. Sox9 is expressed faintly in the medial and highly in the lateral (black arrow) neural crest and in the otic placodes (green arrow). (U) RhoV/Sox9 double in situ hybridization analysis. Note that RhoV is not expressed in the otic placodes stained by Sox9. At the onset of neural tube closure (stage 19, V), expression of RhoV is down-regulated in the neural crest territory. From stage 22 (X, dorsal view, anterior towards the top; Y, lateral view, anterior towards the right), RhoV expression is no longer detected in the neural crest. |
