Phylogenic distribution of sFRPs. From an alignment of sFRPs performed with ClustalW (Thompson et al., 1994), a consensus phylogenetic tree was constructed using the Maximum Parsimony method included in the software Phylowin (Galtier et al., 1996). In terms of amino-acid sequence, sFRP members could be subdivided in four subgroups: sFRP1/5 (red box), sFRP2 (green box), Crescent/Sizzled (blue box) and sFRP3/4 (yellow box). Interestingly, Tlc has not been found clustered in one of these subgroups on the basis of sequence similarity. The zebrafish protein Otx2 is used as an outgroup sequence. Species abbreviations: c, chick (G. gallus); ci, C. intestinalis; h, human (H. sapiens); m, mouse (M. musculus); t, pufferfish (T. nigroviridis); x, xenope (X. laevis); z, zebrafish (D. rerio).

Expression profiles of zebrafish sfrp3. Dorsal with animal pole to the top (A and N), animal pole with anterior to the top (C, E and G), lateral with anterior to the top (B, D, F and H) or lateral with anterior to the left (I-M) views of zebrafish embryos hybridized with sfrp3 antisense probe. White asterisks indicate the anterior part of the involuting mesendoderm. White arrows indicate the mesendoderm prechordal plate. Black asterisks show a group of cells which might be the primordium of the pelvic fin. Abbreviations: dt, digestive tracts; fp, floor plate; hy, hypochord; n, notochord; yt, yolk tube.

Expression profiles of zebrafish sfrp2. Dorsal (F, J and M), lateral with anterior to the left (A-E, H, I, K and L) or transversal (G) views of zebrafish embryos hybridized with sfrp2 antisense probe. White asterisks indicate the adaxial cells and white arrows indicate the dorsal spinal cord. Black asterisks indicate the otic placode and black arrow indicates the pectoral fin.

Early expression profiles of zebrafish sfrp1a. Dorsal with animal pole to the top (C, F, I, L and O), dorsal with anterior to the left (Q, T and U), lateral with anterior to the top (B, E, H, K, N, P, R and S) or animal pole with anterior to the top (A, D, G, J, and M) views of zebrafish embryos hybridized with sfrp1a antisense probe. S, T, and U are double in situ showing sfrp1a in blue and pax6 (S and T) or pax2 (U) in red. White asterisk indicates the pre- and somatic mesoderm. Abbreviations: a, anterior neural plate; h, presumptive hindbrain; m, presumptive midbrain; ov, optic vesicle; t, presumptive telencephalon; tb, tail bud.

Later expression profiles of zebrafish sfrp1a. Dorsal (A, D, F and J), lateral (B, C, E and G-I) or transversal (K and L) views of zebrafish embryos hybridized with sfrp1a antisense probe. Abbreviations: di, diencephalon; h, hindbrain; hy, hypothalamus; m, midbrain; o, otic vesicle; t, telencephalon; te, optic tectum; tm, tegmentum.

Expression profiles of zebrafish sfrp1b. Lateral with anterior to the left (A and B) or ventral with anterior to the left (C) views of zebrafish embryos hybridized with sfrp1b antisense probe. sfrp1b is specifically expressed in the cells lining the posterior tip of the yolk extension (A). Later, sfrp1b marks discrete group of cells on the surface of the yolk (B and C).

Expression profiles of zebrafish sfrp5 inside the CNS. Lateral with anterior to the top (B, D, F, H and J) or to the left (K, L, N and O), dorsal with anterior to the top (A, C, E, G and I), transversal (M) or dorsal with anterior to the left (P) views of zebrafish embryos hybridized with sfrp5 antisense probe. Abbreviations: e, eye; h, hindbrain; hy, hypothalamus; o, otic vesicle; t, telencephalon; te, optic tectum; tm, tegmentum.

Expression profiles of zebrafish sfrp5 outside of the CNS. Dorsal with anterior to the left (A), ventral with anterior to the left (B, C and G), lateral with anterior to the left (D and F) or transversal (E) views of zebrafish embryos at pharyngula stage hybridized with sfrp5 antisense probe. Abbreviations: g, gut; o, otic vesicles; dtv, developing trunk vasculature; vhy indicates the posterior ventral hypothalamus corresponding to the area forming the posterior pituitary.

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