Broun M et al. (1999), Cngsc, a homologue of goosecoid, participates i...

XB-ART-12020

Development 1999 Dec 01;12623:5245-54. doi: 10.1242/dev.126.23.5245.

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Cngsc, a homologue of goosecoid, participates in the patterning of the head, and is expressed in the organizer region of Hydra.

Broun M , Sokol S , Bode HR .

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We have isolated Cngsc, a hydra homologue of goosecoid gene. The homeodomain of Cngsc is identical to the vertebrate (65-72%) and Drosophila (70%) orthologues. When injected into the ventral side of an early Xenopus embryo, Cngsc induces a partial secondary axis. During head formation, Cngsc expression appears prior to, and directly above, the zone where the tentacles will emerge, but is not observed nearby when the single apical tentacle is formed. This observation indicates that the expression of the gene is not necessary for the formation of a tentacle per se. Rather, it may be involved in defining the border between the hypostome and the tentacle zone. When Cngsc(+) tip of an early bud is grafted into the body column, it induces a secondary axis, while the adjacent Cngsc(-) region has much weaker inductive capacities. Thus, Cngsc is expressed in a tissue that acts as an organizer. Cngsc is also expressed in the sensory neurons of the tip of the hypostome and in the epithelial endodermal cells of the upper part of the body column. The plausible roles of Cngsc in organizer function, head formation and anterior neuron differentiation are similar to roles goosecoid plays in vertebrates and Drosophila. It suggests widespread evolutionary conservation of the function of the gene.

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Species referenced: Xenopus
Genes referenced: alx4 arx gsc mix1 msx1 otx2 pax3 pax6 pax7 tbx2

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	Fig. 1. Amino acid sequence alignments of (A) the homeodomains of Goosecoid proteins, and (B) GEHdomains of Goosecoid and other proteins. Dashes indicate residues identical with Cngsc in A and with the consensus sequence in B. (A) Homeodomains of hydra (Cngsc), Drosophila (D-gsc) (Goriely et al., 1996), zebrafish (Zgsc) (Stachel et al., 1993), Xenopus (Xgsc) (Blumberg et al., 1991) and chicken (gsc and gsx) (Izpisua-Belmonte et al., 1993; Lemaire et al., 1997) goosecoid proteins, and zebrafish (dharma) (Yamanaka et al., 1998) and mouse (gsclMM) (Galili et al., 1997) goosecoid-like proteins. The diagnostic lysine residue (K50) is in bold. (B) GEH-domains of goosecoid proteins of hydra (Cngsc), Drosophila (Dgsc) and Xenopus (Xgsc); msh proteins of hydra (Cnmsx) (McCord and H. R. B., unpublished data), Drosophila (msh) (Isshiki et al., 1997) and M. musculus (msx-1) (Kuzuoka et al., 1994); engrailed proteins of Drosophila (Poole et al., 1985) and C. elegans (Wilson et al., 1994); and NK-2 proteins of hydra (Grens et al., 1996) and Drosophila (Nirenberg et al., 1995).
	Fig. 2. Phylogenetic analysis of paired-like class proteins using parsimony. See Materials and Methods for details. The Genbank accession numbers for the sequences are as follows: Dgsc DM (U52968); Xgsc XL (M81481); gsc ZF (L03394); gsx Gg (Y09850); gscl MM (U70231); dharma ZF (AB010103); Arx MM (AB006103); Alx4 MM (AF001465); Pax6 MM (X63963), eyeless DM (X79493); Otd DM (X58983); Otx2 XL (Z46972); Mix1 XL (1170320); Otlx MM (U80036); Ptx DM (AJ001519); Pax3 MM (AF014366); Pax7 MM (1352721), Prd DM (M14548).
	Fig. 3. Embryos injected with Cngsc mRNA into a single ventrovegetal blastomere at a 4-8 cell stage. The induced secondary axises are indicated with the arrows. A control embryo is shown at the bottom of the picture.