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Development 2004 Jun 01;13111:2653-67. doi: 10.1242/dev.01129.
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Multiple points of interaction between retinoic acid and FGF signaling during embryonic axis formation.

Shiotsugu J , Katsuyama Y , Arima K , Baxter A , Koide T , Song J , Chandraratna RA , Blumberg B .

Anteroposterior (AP) patterning of the developing CNS is crucial for both regional specification and the timing of neurogenesis. Several important factors are involved in AP patterning, including members of the WNT and FGF growth factor families, retinoic acid receptors, and HOX genes. We have examined the interactions between FGF and retinoic signaling pathways. Blockade of FGF signaling downregulates the expression of members of the RAR signaling pathway, RARalpha, RALDH2 and CYP26. Overexpression of a constitutively active RARalpha2 rescues the effects of FGF blockade on the expression of XCAD3 and HOXB9. This suggests that RARalpha2 is required as a downstream target of FGF signaling for the posterior expression of XCAD3 and HOXB9. Surprisingly, we found that posterior expression of FGFR1 and FGFR4 was dependent on the expression of RARalpha2. Anterior expression was also altered with FGFR1 expression being lost, whereas FGFR4 expression was expanded beyond its normal expression domain. RARalpha2 is required for the expression of XCAD3 and HOXB9, and for the ability of XCAD3 to induce HOXB9 expression. We conclude that RARalpha2 is required at multiple points in the posteriorization pathway, suggesting that correct AP neural patterning depends on a series of mutually interactive feedback loops among FGFs, RARs and HOX genes.

PubMed ID: 15128657
Article link: Development
Grant support: [+]

Species referenced: Xenopus
Genes referenced: aldh1a2 cdx1 cdx2 cdx4 cyp26a1 fgf8 fgfr1 fgfr4 hoxb9 hoxc9-like rab40b rara rarb tbxt wnt8a
Morpholinos: rara MO2 rara MO4

Article Images: [+] show captions