Direct Reciprocal Repression between Goosecoid and Ventx1.1 Modulates Dorsoventral Patterning in Xenopus

Precise dorsoventral patterning in Xenopus embryos depends on coordinated transcriptional regulation between organizer and ventral genes. Goosecoid (Gsc) promotes dorsal identity, whereas Ventx1.1, a downstream effector of BMP signaling, specifies ventral fate. Although their antagonistic relationship has been described, the cis-regulatory basis underlying their reciprocal repression has not been clearly defined. Here, we demonstrate that Gsc and Ventx1.1 reciprocally repress each other's transcription through specific cis-regulatory elements within their promoters. Serial promoter deletions and site-directed mutagenesis identified a functional Goosecoid response element (GRE) in the ventx1.1 promoter and Ventx1.1 response elements (VREs) in the gsc promoter. Mutation of these elements markedly reduced reciprocal repression in luciferase assays, and Chromatin immunoprecipitation revealed enrichment at the corresponding promoter regions during gastrulation. In addition, the neuroectoderm-specific transcription factor Foxd4l1.1 also repressed gsc, indicating an additional layer of transcriptional control that refines spatial gene expression. Together, these findings identify a promoter-level reciprocal repression circuit between Gsc and Ventx1.1 and suggest that this circuitry contributes to the refinement of dorsoventral patterning in Xenopus gastrulae.