Sox3 expression is maintained by FGF signaling and restricted to the neural plate by Vent proteins in the Xenopus embryo.
The formation of the nervous system is initiated when ectodermal cells adopt the neural fate. Studies in Xenopus demonstrate that inhibition of BMP results in the formation of neural tissue. However, the molecular mechanism driving the expression of early neural genes in response to this inhibition is unknown. Moreover, controversy remains regarding the sufficiency of BMP inhibition for neural induction. To address these questions, we performed a detailed analysis of the regulation of the soxB1 gene, sox3, one of the earliest genes expressed in the neuroectoderm. Using ectodermal explant assays, we analyzed the role of BMP, Wnt and FGF signaling in the regulation of sox3 and the closely related soxB1 gene, sox2. Our results demonstrate that both sox3 and sox2 are induced in response to BMP antagonism, but by distinct mechanisms and that the activation of both genes is independent of FGF signaling. However, both require FGF for the maintenance of their expression. Finally, sox3 genomic elements were identified and characterized and an element required for BMP-mediated repression via Vent proteins was identified through the use of transgenesis and computational analysis. Interestingly, none of the elements required for sox3 expression were identified in the sox2 locus. Together our data indicate that two closely related genes have unique mechanisms of gene regulation at the onset of neural development.
Rogers
Crystal D
CD
Department of Biology, Georgetown University, Washington, DC 20057, USA.
Archer
Tenley C
TC
Cunningham
Doreen D
DD
Grammer
Timothy C
TC
Casey
Elena M Silva
EM
D000818:Animals; D001483:Base Sequence; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000378:metabolism; D024002:HMGB Proteins / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D054258:Neural Plate / Q000196:embryology* / Q000378:metabolism; D014176:Protein Biosynthesis; D055748:SOXB1 Transcription Factors; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D029867:Xenopus Proteins / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology / Q000378:metabolism; D000099176:Noggin Protein
D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D005346:Fibroblast Growth Factors; D024002:HMGB Proteins; D006609:High Mobility Group Proteins; D018398:Homeodomain Proteins; D055748:SOXB1 Transcription Factors; D014157:Transcription Factors; D029867:Xenopus Proteins; D000099176:Noggin Protein; C527788:Sox3 protein, Xenopus; C527781:sox2 protein, Xenopus; C099992:ventx2.1 protein, Xenopus