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Differential expression of the Groucho-related genes 4 and 5 during early development of Xenopus laevis.
Recently, we demonstrated that the Xenopus Wnt effector XTcf-3 interacts with Groucho-related transcriptional repressors (Roose et al., 1998. Nature 395, 608-612). A long form of the Groucho-related genes, XGrg-4, was shown to repress axis formation in the Xenopus embryo, whereas a short form, XGrg-5, acted as a potentiator. In this study, the temporal and spatial expression of XGrg-4 and XGrg-5 is described in Xenopus laevis embryos. Both genes are maternally expressed. In the gastrula, transcripts of both genes are present in the animal as well as the vegetal region. At later stages, XGrg-4 and XGrg-5 show specific patterns of expression in the central nervous system (CNS), cranial ganglia, eyes, otic vesicles, stomodeal-hypophyseal anlage, cement gland, headmesenchyme, branchial arches, neural crest and derivatives, somites, pronephros, pronephric duct, heart and tailbud. Differences in the expression of XGrg-4 and XGrg-5 were found in the CNS, cranial ganglia, olfactory placodes, stomodeal-pharyngeal anlage, cement gland, headmesenchyme and ectoderm.
Fig. 2. Whole mount in situ hybridization of gastrula stage embryos with antisense XGrg-4 and XGrg-5 probes. Dorsal views of stage 12 embryos (A, B). XGrg-5 expression along the midline is indicated by arrows (B).
Fig. 3. XGrg-4 and XGrg-5 expression in neurula stages. (A,B,D,E,F) Antero-dorsal views. (C) Sagittal section of a stage 16 embryo. (F) XEn-1 (Eizema et al., 1994) marks the mid-hindbrain border region. cg, cement gland, (1) stomato-hypophyseal anlage, (2) anterior neural plate, (3) prospective pros-mesencephalic boundary, (4) rim along the neural groove, (5) prospective anterior rhombencephalon.
Fig. 4. Expression of XGrg-4 in the ectoderm. Speckled expression of XGrg-4 in the ectoderm in stage 25 (B) and transverse section of a stage 22 embryo (A).
Fig. 5. Localization of XGrg-4 and XGrg-5 transcripts in early tailbud stage (22). (A–C) High XGrg-4 expression at the pros-mesencephalic boundary (1), at the mes-rhombencephalic boundary (2) and in the rhombencephalon (3). (D–F) High XGrg-5 expression in the prosencephalon (1), in the anterior rhombencephalon (2) and in the posterior rhombencephalon (3). Arrows in A and D: somites. Asterisks in C and F: mesenchyme between the prospective olfactory placodes. ba, branchial arches; opv, optic vesicle; ov, otic vesicle; p, pronephros; pd, pronephric duct; sha, stomodeal-hypophyseal anlage. Embryos are viewed from lateral (A,D), dorsal (B,E) or anterior (C,F).
Fig. 6. Localization of XGrg-4 and XGrg-5 expression at tailbud stage 35. (A,B) XGrg-4. (C,D) XGrg-5. (1) Pros-mesencephalic boundary, (2) mes-rhombencephalic boundary. V-X: cephalic ganglia V-X. Embryos are viewed from lateral (A,C) or anterior (B,D).