title: Noggin signaling from Xenopus animal blastomere lineages promotes a neural fate in neighboring vegetal blastomere lineages.
abstract: In Xenopus, localized factors begin to regionalize embryonic fates prior to the inductive interactions that occur during gastrulation. We previously reported that an animal-to-vegetal signal that occurs prior to gastrulation promotes primary spinal neuron fate in vegetal equatorial (C-tier) blastomere lineages. Herein we demonstrate that maternal mRNA encoding noggin is enriched in animal tiers and at low concentrations in the C-tier, suggesting that the neural fates of C-tier blastomeres may be responsive to early signaling from their neighboring cells. In support of this hypothesis, experimental alteration of the levels of Noggin from animal equatorial (B-tier) or BMP4 from vegetal (D-tier) blastomeres significantly affects the numbers of primary spinal neurons derived from their neighboring C-tier blastomeres. These effects are duplicated in blastomere explants isolated at cleavage stages and cultured in the absence of gastrulation interactions. Co-culture with animal blastomeres enhanced the expression of zygotic neural markers in C-tier blastomere explants, whereas co-culture with vegetal blastomeres repressed them. The expression of these markers in C-tier explants was promoted when Noggin was transiently added to the culture during cleavage/morula stages, and repressed with the transient addition of BMP4. Reduction of Noggin translation in B-tier blastomeres by antisense morpholino oligonucleotides significantly reduced the efficacy of neural marker induction in C-tier explants. These experiments indicate that early anti-BMP signaling from the animal hemisphere recruits vegetal equatorial cells into the neural precursor pool prior to interactions that occur during gastrulation.
authors.affiliation: Department of Anatomy and Cell Biology, George Washington University, Washington, DC 20037, USA.
authors.forename: Sen
authors.initials: S
authors.lastname: Huang
authors.forename: Bo
authors.initials: B
authors.lastname: Yan
authors.forename: Steven A
authors.initials: SA
authors.lastname: Sullivan
authors.forename: Sally A
authors.initials: SA
authors.lastname: Moody
mesh_terms: D000818:Animals; D001757:Blastomeres / Q000166:cytology* / Q000378:metabolism*; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D019070:Cell Lineage; D004627:Embryonic Induction; D053595:Embryonic Stem Cells / Q000378:metabolism; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008954:Models, Biological; D009046:Motor Neurons / Q000378:metabolism*; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D000099176:Noggin Protein
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D029867:Xenopus Proteins; D000099176:Noggin Protein; C525812:bmp4 protein, Xenopus