title: Suppression of head formation by Xmsx-1 through the inhibition of intracellular nodal signaling.
abstract: It is well established that in Xenopus, bone morphogenetic protein (BMP) ventralizes the early embryo through the activation of several target genes encoding homeobox proteins, some of which are known to be necessary and sufficient for ventralization. Here, we used an inhibitory form of Xmsx-1, one of BMP's targets, to examine its role in head formation. Interestingly, ventral overexpression of a dominant Xmsx-1 inhibitor induced an ectopic head with eyes and a cement gland in the ventral side of the embryo, suggesting that Xmsx-1 is normally required to suppress head formation in the ventral side. Supporting this observation, we also found that wild-type Xmsx-1 suppresses head formation through the inhibition of nodal signaling, which is known to induce head organizer genes such as cerberus, Xhex and Xdkk-1. We propose that negative regulation of the BMP/Xmsx-1 signal is involved not only in neural induction but also in head induction and formation. We further suggest that the inhibition of nodal signaling by Xmsx-1 may occur intracellularly, through interaction with Smads, at the level of the transcriptional complex, which activates the activin responsive element.
authors.affiliation: Department of Developmental Biology, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki, 444-8585, Japan.
authors.forename: T S
authors.initials: TS
authors.lastname: Yamamoto
authors.forename: C
authors.initials: C
authors.lastname: Takagi
authors.forename: A C
authors.initials: AC
authors.lastname: Hyodo
authors.forename: N
authors.initials: N
authors.lastname: Ueno
mesh_terms: D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004707:Endoderm / Q000378:metabolism; D051858:Forkhead Transcription Factors; D018507:Gene Expression Regulation, Developmental; D006257:Head / Q000196:embryology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007424:Intracellular Fluid; D051957:MSX1 Transcription Factor; D009414:Nerve Growth Factors; D015398:Signal Transduction; D051785:Smad Proteins; D051899:Smad2 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; C102067:FOXH1 protein, Xenopus; D051858:Forkhead Transcription Factors; C491117:Foxh1 protein, mouse; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; C497996:MSX1 protein, Xenopus; D009414:Nerve Growth Factors; D051785:Smad Proteins; D051899:Smad2 Protein; C497785:Smad2 protein, Xenopus; D051901:Smad4 Protein; D015534:Trans-Activators; D014157:Transcription Factors; D029867:Xenopus Proteins; C490808:smad4.1 protein, Xenopus; C117263:smad4.2 protein, Xenopus