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Abstract
The iroquois (iro) genes encode evolutionary conserved homeoproteins that participate in many developmental processes [reviewed in Development 128 (2001) 2847]. In Xenopus, the Iro protein Xiro1 is a repressor, required during gastrulation for neural plate formation, that downregulates Bmp4. During neurulation, Xiro1 participates in the pattering of the neuroectoderm. In this work, we report the cloning and pattern of expression of XCoREST, another gene repressed by Xiro1. During Xenopus development, XCoREST is expressed in territories in which neurogenesis takes place.
Fig. 2. Expression of XCoREST during Xenopus development. (A) At the beginning of neurulation (stage 13), XCoREST mRNA is localized in two stripes of cells at each side of the midline (arrowheads). (B) At stage 14, the expression of XCoREST is detected in three stripes (M, medial; I, intermediate and L, lateral stripes; arrowheads) at each side of the midline and in the trigeminal placode (tg). (C) N-tubulin is expressed in a similar three-stripe pattern (arrowheads). (D) Double in situ hybridization for XCoREST (purple) and N-tubulin (cian) mRNAs. (E) Upper panel shows a higher magnification of the stripe pointed at with an arrowhead in (D). Lower panel shows the same stripe of the same embryo after the first chromogenic reaction for N-tubulin detection (cian) and before the second chromogenic reaction for XCoREST detection (purple). (F–H) XCoREST expression at different neurula stages. (I–K) Lateral views. (I) At stage 21, XCoREST mRNA is also detected in the eye (arrowhead) and brain (arrow). This expression is also seen at later stages (J and K). (L) Double in situ for XCoREST (pink) and Xiro1 (cian) mRNAs. Note that XCoRESTmedial and intermediate stripes (arrowheads) are at the border of Xiro1 expression domains (arrow). (M–P) Hindbrain transverse sections of tailbud embryos showing XCoREST (M), Xngnr-1 (N), XDelta-1 (O) and N-tubulin (P) domains of expression (arrowheads).
