Fletcher RB et al. (2004), Expression of Xenopus tropicalis noggin1 and no...

XB-ART-2676

Gene Expr Patterns 2004 Dec 01;52:225-30. doi: 10.1016/j.modgep.2004.08.001.

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Expression of Xenopus tropicalis noggin1 and noggin2 in early development: two noggin genes in a tetrapod.

Fletcher RB , Watson AL , Harland RM .

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We report the identification of two distinct noggin genes in the tetrapod Xenopus tropicalis. Noggin functions to antagonize BMP signaling in many developmental contexts, and much work has explored its role in early vertebrate development. We have identified two noggin genes in the tropical clawed frog, X. tropicalis, a diploid anuran which is being explored for its potential as a genetic model system for early vertebrate development. Here we report the cloning and characterization of the Xenopus tropicalis noggin1 and noggin2 genes, which have distinct expression domains in the early embryo with one overlapping domain in the anterior neural tissue. X. tropicalis noggin1 expression is very similar to that of noggin in Xenopus laevis, with expression beginning in the blastula organizer region and continuing through gastrulation and neurulation in the organizer and notochord. Later, it is also expressed in the anterior neural ridge and subsequent forebrain; noggin1 is also expressed in the pharyngeal arches after neural tube closure. At the tadpole stage expression is maintained in the dorsal neural tube and is present in the otic vesicle. However, the expression of noggin2 is much more similar to the expression of noggin2 in D. rerio with expression in the forebrain, hindbrain, and somites, but unlike D. rerio, X. tropicalis noggin2 is expressed in the heart by stage 28. This work presents the first example of a tetrapod with at least two noggin genes.

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Species referenced: Xenopus tropicalis Xenopus laevis
Genes referenced: nog nog2 odc1

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	Fig. 2. X. tropicalis noggin1 whole-mount in situ hybridization expression profile. All embryos are oriented with anterior to the left at the indicated stages. (A) is photographed uncleared; all other embryos are photographed after clearing in BB/BA. (A,E,G,I,J,L,N) are dorsal views; (B,D,F,H,M,O) are lateral views; (C) is an animal pole view; (K) is an anterior view. b, blastocoel; dm, dorsal marginal zone; o, organizer; nc, notochord; anr, anterior neural ridge; fb, forebrain; pa, pharyngeal arches; nt, neural tube.
	Fig. 3. X. tropicalis noggin2 whole-mount in situ hybridization expression profile. (A,B,J) were photographed uncleared; (C,D,E) were photographed partially cleared in glycerol, and all other embryos were photographed after clearing in BB/BA. (A,E,F) are anterior views, dorsal upward; (B,C,H–K) are lateral views; (D,G) are dorsal views. Embryos are oriented anterior to the left at the indicated stages. anr, anterior neural ridge; fb, forebrain; hb, hindbrain; s, somites.
	Fig. 4. Expression profile of noggin1 and noggin2 at tadpole stages. (A–F) noggin1 expression at the indicated stages. (G–M) noggin2 at the indicated stages. Embryos are oriented anterior to the left. (I) is a dorsal view; all others are lateral views. (A,G) are uncleared; all others are cleared in BB/BA; (F,J,K) are photographed with Nomarsky optics. fb, forebrain; pa, pharyngeal arches; nc, notochord; nt, neural tube; e, eye; ov, otic vesicle; tb, tailbud; hb, hindbrain; s, somites; h, heart; l, liver primordium.
	Fig. 1. Sequence comparison of X. tropicalis noggin1 and noggin2 and temporal expression profile. (A) Amino acid alignment of X. tropicalis noggin1 and noggin2 with M. musculus noggin, and D. rerio noggin1 and noggin2. Colons represent residues conserved between all five noggin sequences. Light shading represents residues conserved only between mouse noggin and zebrafish and X. tropicalis noggin1. Dark shading represents residues conserved only between noggin2 genes. (B) An unrooted dendrogam demonstrating that X. tropicalis noggin1 shares the highest sequence homology with X. laevis noggin and M. mus noggin while X. tropicalis noggin2 shares more sequence similarity with the noggin2 genes of zebrafish (D. rerio) and fugu (f. rugibes); g.g., gallus gallus. (C) RT-PCR temporal expression profile of whole embryos at the indicated stages; ODC was used as a loading control.
	nog (noggin) gene expression n bisected Xenopus tropicalis embryo, mid-sagittal section, assayed via in situ hybridization, NF stage 10.25, dorsal left, animal pole up.
	nog (noggin) gene expression in bisected Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 13/14, lateral view, anterior left, dorsal up.
	nog (noggin) gene expression in bisected Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 19, lateral view, anterior left, dorsal up.
	nog (noggin) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 28, lateral view, anterior left, dorsal up.

	nog2 (noggin 2) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 15, anterior view, dorsal up.
	nog2 (noggin 2) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 17, dorsal view, anterior left.
	nog2 (noggin 2) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 19, anterior view, dorsal up.
	nog2 (noggin 2) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 25, head and trunk region, lateral view, anterior left, dorsal up.
	nog2 (noggin 2) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 28, lateral view, anterior left, dorsal up.
	nog2 (noggin 2) gene expression in Xenopus tropicalis embryo, assayed via in situ hybridization, NF stage 32, head and trunk region only, lateral view, anterior upper left, dorsal up (right).