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Display additional annotations [+]
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Fig. 10. Model of signalling input into the LPM of the neurula stage Xenopus embryo. A high level of RA signalling input is suggested by the expression domain of raldh2 in the anterior and dorsal LPM (A). Conversely, Fgf signalling is proposed in the anterior-ventral and posterior-ventral LPM, suggested by the expression domains of fgf8 in the anterior, and fgf4 and fgf8 in the posterior pole of the embryo. Dark blue and yellow bars represent the expression of raldh2 and fgf ligands respectively, while blue and yellow arrows depict the proposed area which RA (blue) and fgf (yellow) are required for normal patterning. The model depicts a left lateral view of the LPM. Ant: anterior, Dor: dorsal, Lat: lateral view, Pos: posterior, Ven: ventral. (B) Diagrammatical representation of LPM expression domain response to decrease in either RA (left) or Fgf (right) signalling when compared with the DMSO control (centre). The anterior-dorsal and middle LPM domains require RA signalling for their full expression domain. When embryos are treated with the RA antagonist the anterior-dorsal domain is restricted (a) and the middle LPM domain is contracted (b). When Fgf signalling is inhibited the anterior-dorsal domain is expanded ventrally (c) and the posterior domains are severely restricted (d), indicating that the anterior-ventral and posterior LPM domains are dependant on Fgf signalling. Red: nkx2.5, blue: foxf1, yellow: hand1, green: sall3, purple: Xbra. |
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Display additional annotations [+]
| Gene |
Clone |
Species |
Stages |
Anatomy |
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fgf8
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laevis
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NF stage 18
to
NF stage 20
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posterior neural tube
,
neural tube
,
presumptive midbrain-hindbrain boundary
,
preplacodal ectoderm
,
anterior neural ridge
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spry2
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laevis
|
NF stage 18
to
NF stage 20
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neuroectoderm
,
neural tube
,
presumptive midbrain-hindbrain boundary
,
neural fold
,
preplacodal ectoderm
,
[+]
|
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cyp26a1
|
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laevis
|
NF stage 18
to
NF stage 20
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mesoderm
,
axial mesoderm
,
paraxial mesoderm
,
posterior
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aldh1a2
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|
laevis
|
NF stage 18
to
NF stage 20
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optic vesicle
,
lateral plate mesoderm
,
anterior dorsal lateral plate region
,
dorsal lateral plate mesoderm
|
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Fig. 7. The RA and Fgf pathways regulate each other. The levels of RA signalling (AI) were altered by addition of a synthetic RA antagonist (left column) or all-trans RA (right column) and compared to a DMSO control (centre column). Embryos were assayed for fgf4 (AC) and fgf8 (DI) expression. The posterior domain of fgf4 (a) is lost in RA treated embryos (C) when compared to the control (B), but unaffected in embryos treated with RAA. Expression of fgf8 is expanded both anteriorly (E and F) and posteriorly (H and I; compare distance between arrowheads (d) marking the anterior limits of domain, and (e) marking posterior limits of domain) under treatment with RA. Decreasing RA signalling also reduces the anterior domain of fgf8 underlying the heart region (compare ratio of staining intensity between (b) marking the pituitary anlagen to (c)). A similar effect is seen with sprouty2 expression (JO), as its domain is increased with RA in both the anterior heart region (L; arrowhead f) and it extends further anterior (g) in the dorsal neural tube (O) when compared to controls (KN). Conversely, embryos were treated with SU5402 and assayed for expression of aldh1a2 (P and Q) or cyp26 (R and S) to determine the effect of a loss of Fgf signalling on the RA signalling pathway. The expression domain of aldh1a2 was expanded posterior (Q) (arrowhead: h marking posterior limit of expression domain) as compared to control embryos (P). Cyp26, normally present in the posterior LPM tailbud domain (R; arrowhead i) is undetectable when Fgf signalling is inhibited (S). Ant: anterior view with dorsal at top of image. Dor: dorsal view with anterior at top. Llv: left lateral view with anterior toward left, dorsal at top of image. Pos: posterior view with dorsal at top. The total number of embryos examined for each panel is indicated in the lower left hand corner.
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