XB-ART-16543Development May 1, 1997; 124 (10): 2075-85.
Expression of Pax-3 is initiated in the early neural plate by posteriorizing signals produced by the organizer and by posterior non-axial mesoderm.
Pax-3 is a paired-type homeobox gene that is specifically expressed in the dorsal and posterior neural tube. We have investigated inductive interactions that initiate Pax-3 transcript expression in the early neural plate. We present several lines of evidence that support a model where Pax-3 expression is initiated by signals that posteriorize the neuraxis, and then secondarily restricted dorsally in response to dorsal-ventral patterning signals. First, in chick and Xenopus gastrulae the onset of Pax-3 expression occurs in regions fated to become posterior CNS. Second, Hensen''s node and posterior non-axial mesoderm which underlies the neural plate induce Pax-3 expression when combined with presumptive anterior neural plate explants. In contrast, presumptive anterior neural plate explants are not competent to express Pax-3 in response to dorsalizing signals from epidermal-ectoderm. Third, in a heterospecies explant recombinant assay with Xenopus animal caps (ectoderm) as a responding tissue, late, but not early, Hensen''s node induces Pax-3 expression. Chick posterior non-axial mesoderm also induces Pax-3, provided that the animal caps are neuralized by treatment with noggin. Finally we show that the putative posteriorizing factors, retinoic acid and bFGF, induce Pax-3 in neuralized animal caps. However, blocking experiments with a dominant-inhibitory FGF receptor and a dominant-inhibitory retinoic acid receptor suggest that Pax-3 inductive activities arising from Hensen''s node and posterior non-axial mesoderm do not strictly depend on FGF or retinoic acid.
PubMed ID: 9169853
Article link: Development
Genes referenced: en2 fgf2 nog pax3
Article Images: [+] show captions
|Fig. 2. Whole-mount in situ hybridization analysis of Pax-3 expression in Xenopus embryos. (A) Dorsovegetal and, (B) lateral view at stage 11.5 showing that Pax-3 is expressed in distinct lateral domains of the presumptive neural plate. (C) Dorsal view at stage 12 showing the refinement of Pax-3 expression to lateral domains of the neural plate during convergence and extension. (D) Transverse paraffin section of a stage 16 embryo, showing that Pax-3 expression is restricted to the lateral neural plate (arrow), overlying somitic and lateral plate mesoderm. (E) Dorsoanterior view of a stage 18 embryo hybridized with Pax-3 (light blue, rostral extent indicated by a white arrow) and en-2 (purple, indicated by a black arrow) showing that Pax-3 expression extends just rostral to the mb-hb boundary. n, notochord; s, somite. Scale bars, (A-C, E) 200 μm; (D) 100 μm.|