The initiation of Hox gene expression in Xenopus laevis is controlled by Brachyury and BMP-4.
Hox genes encode a family of transcription factors that specify positional identities along the anterior-posterior (AP) axis during the development of vertebrate embryos. The earliest Hox expression in vertebrates is during gastrulation, at a position distant from the organiser or its equivalent. However, the mechanism that initiates this early expression is still not clear. Guided by the expression pattern, we identified upstream regulators in Xenopus laevis. The mesodermal transcription factor brachyury (Xbra) controls the early Hox expression domain in the animal-vegetal direction and the secreted growth factor BMP-4 limits it in the organiser/non-organiser direction. The overlap of these two signals, indicated by a Cartesian coordinate system, defines the initial Hox expression domain. We postulate that this system is a general mechanism for the activation of all Hox genes expressed during gastrulation.
Wacker
S A
SA
Hubrecht Laboratory, Netherlands Institute for Developmental Biology, 3584 CT Utrecht, The Netherlands.
McNulty
C L
CL
Durston
A J
AJ
D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D005326:Fetal Proteins / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D005801:Genes, Homeobox; D017403:In Situ Hybridization; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D020825:T-Box Domain Proteins / Q000502:physiology*; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000235:genetics*; D000098908:Brachyury Protein
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D005326:Fetal Proteins; D012333:RNA, Messenger; D020825:T-Box Domain Proteins; D029867:Xenopus Proteins; D000098908:Brachyury Protein; C116765:TBXT protein, Xenopus; C525812:bmp4 protein, Xenopus