XB-ART-38643Dev Dyn January 1, 2009; 238 (1): 194-203.
Cloning and expression analysis of the anterior parahox genes, Gsh1 and Gsh2 from Xenopus tropicalis.
Gsx class proteins are members of the ParaHox homeodomain transcription factor family with conserved roles in specification and patterning of the nervous system. We report the cloning of two Gsx genes, Gsh1 and Gsh2, from the frog Xenopus tropicalis. We demonstrate the existence of a single, intact Xenopus ParaHox cluster, containing Gsh1, Pdx, and Cdx2, plus three degenerate clusters containing Gsh2, Cdx1, and Cdx4. Anterior expression boundaries of genes from the intact ParaHox cluster are co-linear with respect to their genomic organization. We show that Gsh1 and Gsh2 exhibit complex, overlapping patterns of expression within the anterior nervous system from open neural plate stages. We also find that expression of Gsh2, Nkx6, and Msx1 across the medio-lateral axis of the amphibian neural plate is strikingly similar to that of related genes in the Drosophila neuroectoderm. These findings provide further evidence for a conserved pathway regulating dorso-ventral patterning in the Bilateria.
PubMed ID: 19097192
Article link: Dev Dyn
Species referenced: Xenopus
Genes referenced: cdx1 cdx2 cdx4 dlc dlx5 en2 gsx1 gsx2 irx3 isl1 lbx1 lhx9 lox msx1 nkx6-1 pdx1 pth rpe sox3 tec tubb2b
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|Figure 1. The Xenopus tropicalis ParaHox cluster. A: Diagram of ParaHox clusters from amphioxus, mouse, human, and X. tropicalis (not to scale). Arrows denote the transcription orientation of the genes. The X. tropicalis cluster diagram indicates exon/intron structure. B: One-colour triple WISH on a stage 30 X. tropicalis embryo with probes for Xt Gsh1, Xt Pdx1, and Xt Cdx2. C: The remnants of the four X. tropicalis ParaHox clusters, showing some of the flanking genes and approximate distances. Gsx genes are shown in green, Xlox in blue, Cdx in red, Chic in pink, and tyrosine kinase receptors in brown.|
|Figure 2. Developmental expression of Gsh1 [now called gsx1] . A-J, P-W: Gsh1 WISH. K-O: Double WISH as indicated. L, N, S-V: Cleared embryos. K, M, O-R, S (inset): Microtome sections (14 mu m). A: Dorsal, early neurula stage 14. B: Dorso-anterior, mid-neurula stage 17. C: Dorsal, late neurula stage 19. D: Lateral, stage 19. E: Lateral, early tailbud stage 25. F: Dorsal, stage 25. G: Anterior, stage 25. H-S: Tailbud stage 31. H: Lateral. I: Dorsal. J: Anterior. K: Sagittal section through head. L: Head, lateral. M: Anterior hindbrain, transverse section. N: Head, lateral. O, P: Anterior forebrain, transverse sections. Q: Mid forebrain, transverse section. R: Posterior forebrain, transverse section. S: Head, lateral; inset, anterior forebrain section. T: Head, lateral, tailbud stage 35. U: Anterior spinal cord, lateral, late tailbud stage 40. V: Head, dorsal, larval stage 47. W: Midbrain, transverse section, stage 47. Key: ant, anterior; fmb, forebrain-midbrain boundary; hb, hindbrain; hyp, hypothalamus; lge, lateral ganglionic eminence; mge, medial ganglionic eminence; mhb, midbrain-hindbrain boundary; nc, notochord; ob, olfactory bulb; ov, otic vesicle; post, posterior; pt, pretectum; r1, rhombomere 1; r6, rhombomere 6; se, septum; sc, spinal cord; tec, tectum; tel, telencephalon; th, thalamus; vz, ventricular zone; zli, zona limitans intrathalamica.|
|Figure 3. Developmental expression of Gsh2 [now called gsx2] . A-O, Q-T, V-A2: Gsh2 WISH. P, U: Double WISH as indicated. Q, V, X: Cleared embryos. I-L: Transverse vibratome sections (40-50 mu M). R-U, W, Y-A2: Transverse microtome sections (14 mu m). A: Dorsal, late gastrula stage 13. B: Dorsal, mid-neurula stage 17. C: Anterior, stage 17. D, E: Stage 21. D: Lateral. E: Bisected through hindbrain. F-H: Early tailbud stage 25. F: Dorsal. G: Anterior. H: Lateral. I-L: Sections through: (I) forebrain, early tailbud stage 24, (J) eye, tailbud stage 31, (K) anterior trunk, stage 24, (L) posterior trunk, tailbud stage 27. M-O: Stage 30. M: Lateral. N: Anterior. O: Dorsal. P: Head, lateral stage 31. Q: Head, lateral, tailbud stage 29. R-T: Serial sections through forebrain. U: Section through posterior hindbrain, stage 31. V: Head, dorsal, late tailbud stage 40. W: Frontal section through head, stage 40. X-A2: Larval stage 47. X: Head, dorsal. Y-A2: Sections through: (Y) LGE, (Z) prethalamus, (A2) ventral pharynx. Key: en, lateral endoderm; hb, hindbrain; lge, lateral ganglionic eminence; mge, medial ganglionic eminence; nc, notochord; ob, olfactory bulb; pth, prethalamus; r8, rhombomere 8; r7-8, rhombomeres 7-8; rpe, retinal pigment epithelium; sc, spinal cord; vp, velar plate; vz, ventricular zone; zli, zona limitans intrathalamica.|
|Figure 4. Expression of Gsh2 in primary interneuron territory. All embryos early neurula stage 14-15. A, B, C, K, L: Single WISH, probes as indicated. D-J: Double WISH, probes as indicated. A-D: Dorsal views. E: High-power view of lateral margin of neural plate. F, I, J: Transverse vibratome sections (50 mu M) through the neural plate, midline towards the left. H: Dorso-lateral view with anterior to the left. J: Diagram showing transverse section through Drosophila neuroectoderm and Xenopus neural plate. Expression domains of orthologous genes are colored the same. In both cases, dorsal is to the top.|
|gsx1 (GS homeobox 1) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 28, lateral view, anterior left, dorsal up. (note: triple ISH with cdx2 and pdx1 gene expression also shown).|
|Supp. Fig. 3. Gsh1 and Gsh2 expression in the tailbud stage X. tropicalis brain. Diagram of a stage 31 to 32 X. tropicalis brain, viewed laterally, showing the expression patterns of Gsh1 (magenta) and Gsh2 (blue). Hatching indicates overlap of the expression patterns. di, diencephalon; et, eminentia thalami; hyp, hypothalamus; lge, lateral ganglionic eminence; mes, mesencephalon [midbrain]; mge, medial ganglionic eminence; nc, notochord; ob, olfactory bulb; os, optic stalk; ov, otic vesicle; pa, pallium; pi, pineal gland; pt, pretectum; pth, prethalamus; r1 to r8, rhombomeres 1 to 8; rhomb, rhombencephalon [hindbrain]; tec, tectum; sc, spinal cord; tel, telencephalon; th, thalamus; zli, zona limitans intrathalamica.|
|gsx1 (GS homeobox 1, previously called gsh1) and lhx9 (LIM homeobox 9) gene expression in the brain of a Xenopus laevis embryo, assay as double WISH, at NF stage 31. At this stage lhx9 (turquoise) is expressed in thalamus (th) and forebrain-midbrain boundary (fmb), while gsh1/gsx1 (purple) is expressed in the pituitary gland (pt) and [optic] tectum (tec).|
|gene expression of gsh1/gsx1 and gsh2/gsx2 in the developing brain of a Xenopus embryo at NF stage 31. key: lge: lateral ganglionic eminence; mge: medial ganglionic eminence, pth: prethalamus; th: thalamus.|
|Developmental expression of gsh1, and en2.Sagittal section through head.|
|Developmental expression of gsh1, and dll3. Anterior forebrain, transverse sections.|