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Dev Dyn
2004 Aug 01;2304:700-7. doi: 10.1002/dvdy.20040.
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Expression patterns of Xenopus FGF receptor-like 1/nou-darake in early Xenopus development resemble those of planarian nou-darake and Xenopus FGF8.
Hayashi S
,
Itoh M
,
Taira S
,
Agata K
,
Taira M
.
???displayArticle.abstract??? Fibroblast growth factors (FGFs) mediate many cell-to-cell signaling events during early development. Nou-darake (ndk), a gene encoding an FGF receptor (FGFR)-like molecule, was found to be highly and specifically expressed in the head region of the planarian Dugesia japonica, and its functional analyses provided strong molecular evidence for the existence of a brain-inducing circuit based on the FGF signaling pathway. To analyze the role of ndk during vertebrate development, we isolated the Xenopus ortholog of ndk, the vertebrate FGFR-like 1 gene (XFGFRL1). Expression of XFGFRL1/Xndk was first detected in the anterior region at the late gastrula stage and dramatically increased at the early neurula stage in an overall anterior mesendodermal region, including the prechordal plate, paraxial mesoderm, anteriorendoderm, and archenteron roof. This anterior expression pattern resembles that of ndk in planarians, suggesting that the expression of FGFRL1/ndk is conserved in evolution between these two distantly diverged organisms. During the tail bud stages, XFGFRL1/Xndk expression was detected in multiple regions, including the forebrain, eyes, midbrain-hindbrain boundary, otic vesicles, visceral arches, and somites. In many of these regions, XFGFRL1/Xndk was coexpressed with XFGF8, indicating that XFGFRL1/Xndk is a member of the XFGF8 synexpression group, which includes sprouty, sef, and isthmin.
Figure 3. Spatiotemporal expression of XFGFRL1/Xndk at late gastrula to neural tube stages visualized by whole-mount in situ hybridization. Hybridization probes used for XFGFRL1 and XFGF8 are as indicated in the pictures (XFGFRL1 in black; XFGF8 in blue). ldquo cleared, rdquo embryos were treated with benzyl benzoate/benzyl alcohol to become transparent. Numbers indicate developmental stages (Nieuwkoop and Faber, [1967]). A: Lateral view of late gastrula. Anterior toward the left; dorsal is upward. B: Lateral view of early neurula. Anterior toward the left; dorsal is upward. C: Sagittal section of early neurula (stage 13/14). D: Transverse section of early neurula (stage 13/14). The section corresponds to the position shown by a line with d in B. E: Anterolateral (left) and lateral view (middle; anterior toward the left; dorsal is upward) of XFGFRL1 and XFGF8 (right) expression at neurula. Arrowhead, ventrolateral expression in a crescent shape. F,G: Horizontal (F) or transverse (G) section of neurula (stage 17/18). The planes of section are indicated by a line with f or g in E. Arrowheads in lower panels indicate that crescent-shaped expression (see E, right panel) is seen in the sensorial layer of epidermis. H: Sagittal section of neurula (stage 17/18). I: Lateral (left and middle panels; anterior toward the left; dorsal is upward) and anterior view (right panels; dorsal is upward) of neural tube stage embryos. Crescent-shaped expression (see E, right panel) is separated into two stripes as indicated by arrowheads (see I, lower panels). C,D,F-H: Sections of stained embryos are shown in brightfield (left) and DAPI (4 prime ,6-diamidine-2-phenylidole) staining (right). XFGFRL1, Xenopus fibroblast growth factor receptor-like 1; XFGF8, Xenopus fibroblast growth factor-8; ae, anteriorendoderm; anr, anterior neural ridge; ar, archenteron roof; bc, blastocoel; ey, eye; fb, forebrain; lp, lateral plate; mhb, midbrain-hindbrain boundary; no, notochord; op, otic placode; pcp, prechordal plate; pm, paraxial mesoderm; sm, somitic mesoderm. Scale bars = 200 mu m in C,D,F-H.
Figure 4. Spatiotemporal expression of XFGFRL1/Xndk and XFGF8 at tail bud stages visualized by whole-mount in situ hybridization. The expression of XFGFRL1 is compared with that of XFGF8 as indicated (XFGFRL1 in black; XFGF8 in blue). ldquo cleared, rdquo embryos were treated with benzyl benzoate/benzyl alcohol to become transparent. A,B: Lateral view. Anterior toward the left; dorsal is upward. Arrowheads (right panels; see also C, right panel) indicate the region that probably corresponds to the boundary of prosomeres 2 and 3 in the diencephalon (see text). C-H: Comparison of XFGFRL1 (left or upper panel) and XFGF8 (right or lower panel) expression by horizontal or transverse (F, upper panel) sections of stage 33/34 (C-G) and stage 26 (H) embryos. C: Expression in the midbrain-hindbrain boundary. Middle panels are enlargement of left panel, showing that XFGFRL1 is expressed in the pineal gland. D: Forebrain expression. XFGF8 is also expressed in anteriorheadmesenchyme (right panel). E: Eye expression in whole embryos (left panels) and in horizontal sections (middle and right panels). Left panels show enlargement of the head region of the embryos in B. The sections correspond to the position shown by a line with e in left panels. White dotted lines show the outline of the eyes (upper left panel) and the ciliary margin and commissural plate (lower middle panel). White arrowheads show XFGF8 expression in the eye and commissural plate (lower left panel). F: Otic vesicle expression. XFGFRL1 (upper panel) is expressed in ventral and XFGF8 (lower panel) is expressed in the anterior part of the otic vesicles. G: Visceral arch expression. Middle and right panels show enlargement of left panels. Both XFGFRL1 and XFGF8 are expressed in the visceral pouches as indicated by arrows. Turquoise staining seen in the expression of XFGFRL1 was due to depletion of nitro blue tetrazolium inside of embryos by strong staining of the ectodermal region. Thus, XFGFRL1 expression (shown in blue and turquoise) is wider than that of XFGF8. H: Somite expression. Staining is localized to nuclear and perinuclear regions as indicated by arrows. XFGFRL1, Xenopus fibroblast growth factor receptor-like 1; XFGF8, Xenopus fibroblast growth factor-8; cm, ciliary margin; cp, commissural plate; ey, eye; fb, forebrain; le, lensepithelium; me, mesenchyme; mhb, midbrain-hindbrain boundary; ov, otic vesicle; pd, pronephric duct; pg, pineal gland; pn, pronephros; so, somite; tz, transitional zone; va, visceral arch; vp, visceral pouch. Scale bar = 100 mu m.
fgf8 (fibroblast growth factor 8 (androgen-induced)) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 26, lateral view, anteriorleft, dorsal up.
