Multiple points of interaction between retinoic acid and FGF signaling during embryonic axis formation.
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.
Shiotsugu
Jason
J
Department of Developmental and Cell Biology, University of California, Irvine, CA 92697-2300, USA.
Katsuyama
Yu
Y
Arima
Kayo
K
Baxter
Allison
A
Koide
Tetsuya
T
Song
Jihwan
J
Chandraratna
Roshantha A S
RA
Blumberg
Bruce
B
D000080924:Aldehyde Dehydrogenase 1 Family; D042931:Aldehyde Oxidase; D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001368:Axis, Cervical Vertebra / Q000196:embryology* / Q000378:metabolism; D019521:Body Patterning / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian; D004843:Epistasis, Genetic; D005326:Fetal Proteins / Q000235:genetics / Q000378:metabolism; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051499:Receptor, Fibroblast Growth Factor, Type 4; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism; D050697:Retinal Dehydrogenase; D000072516:Retinoic Acid 4-Hydroxylase; D000072482:Retinoic Acid Receptor alpha; D015398:Signal Transduction; D014212:Tretinoin / Q000378:metabolism*; D014981:Xenopus / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism
C096851:Cdx4 protein, Xenopus; D005326:Fetal Proteins; D018398:Homeodomain Proteins; C491256:Hoxb9 protein, Xenopus; D017468:Receptors, Fibroblast Growth Factor; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D029867:Xenopus Proteins; D051524:Fibroblast Growth Factor 8; D014212:Tretinoin; D005346:Fibroblast Growth Factors; D003577:Cytochrome P-450 Enzyme System; D000072516:Retinoic Acid 4-Hydroxylase; D000445:Aldehyde Oxidoreductases; D000080924:Aldehyde Dehydrogenase 1 Family; D050697:Retinal Dehydrogenase; C493756:aldh1a2 protein, Xenopus; D042931:Aldehyde Oxidase; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051499:Receptor, Fibroblast Growth Factor, Type 4