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mecom (MDS1 and EVI1 complex locus) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 22, lateral view, anterior right, dorsal up.
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mecom (MDS1 and EVI1 complex locus) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 25, lateral view, anterior right, dorsal up.
Key: cnh = chordoneural hinge, pn= pronephric mesechyme, hb = rhombomere of hindbrain, mb= midbrain, vfb= ventral forebrain, dfb= diencephalon, hm=hyoid and mandibular crest
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mecom (MDS1 and EVI1 complex locus) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 28, lateral view, anterior right, dorsal up.
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Fig. 3. Whole mount RNA in situ localization of Evi-1 transcripts during Xenopus development. Anterior is to the right in all panels. Representative cleared embryos of increasing age are shown (A) stage 22, (B) stage 25, (C) stage 28, (D) stage 37. Transverse section planes, Fig. 4(B)E), are indicated by the vertical labeled lines (C). Note in panel (D) the avoidance of the otic vesicle by Evi-l expressing neural crest cells. Faint Evi-l signal is visible over a localized region of the developing foregut in later tadpoles, tentatively identified as the stomach (D). Comparison of Pax8 and Evi-1 expression patterns at stage 23 indicates staining in the pronephric duct anlage (E). Scale bar: 100 mm. Abbreviations: a, archenteron (developing gut cavity); cg, cement gland; cnh, chordoneural hinge; dfb, dorsal forebrain; e, eye, hb, hindbrain; hm, head mesenchyme; mb, midbrain; op, olfactory placode; ov, otic vesicle; pn, pronephric duct; st, developing stomach; vfb, ventral forebrain.
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Fig. 4. Sections of whole mount stage 28 embryo analyzed for Evi-1 expression by whole mount in situ hybridization. Panel (A): sagittal section, anterior to left. Panels (B): transverse sections through planes indicated in Fig. 1(C). The asterisk indicates an area of yolky endoderm lost during sectioning. Scale bar: 100 mm. Abbreviations: cg, cement gland; e, eye; fb, forebrain; g, gut cavity; hb, hindbrain; hm, head mesenchyme; mb, midbrain; n, notochord; op, olfactory placode; ov, otic vesicle; pfg, pharynx/foregut; pn, pronephric duct; s, stomodeal anlage; sc, spinal cord; so, somite.
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Fig. 5. Single and double label whole mount in situ hybridization of Evi-l with XKrox-20 and En-2. Evi-1 hybridization signal, marked by solid arrows, is detected as a brownish/black reaction product at the midbrain/hindbrain junction. The XKrox-20 signal, marked by open arrows, is seen as a purple reaction product in rhombomeres 3 and 5, and arch 3. Anterior is to the left in all panels except for A, (A) Stage 19 (late neurula) embryos hybridized with Evi-1 or XKrox-20. Evi-1 mRNA is not detected at this stage by in situ hybridization, but a strong XKrox-20 signal is detected in rhombomeres 3 and 5. (B) Stage 23/24 embryos hybridized with Evi-1 or XKrox-20. Evi-1 is expressed in the forebrain and specific regions of the hindbrain. Expression is also seen in the r4-derived neural crest of the hyoid arch, based on the localization of the signal relative to that of XKrox-20 in r3/r5, and arch 3 (bottom embryo). In the top embryo, the embryo is cleared and Evi-1 signal in the second arch on both sides of the embryo is visible, labeled as a2 and (a2). (C) Dorsal view of embryos shown in (B). Evi l expression is detected in the forebrain, r4, and arch 2, as compared to XKrox-20 (bottom embryo). (D) Double label whole mount in situ at stage 25.
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