NEGATIVE AUTOREGULATION OF THE ORGANIZER-SPECIFIC HOMEOBOX GENE GOOSECOID

The homeobox gene goosecoid has been implicated to play a central role in the Spemann organizer tissue of the vertebrate embryo. Misexpressi on of goosecoid on the ventral side of a Xenopus laevis gastrula embry o was shown to result in a partial duplication of the primary body axi s, reminiscent of the Spemann organizer graft, Normal embryonic develo pment thus requires tight temporal and spatial control of genes instru mental for organizer function. In the present study we investigated th e transcriptional control of goosecoid gene expression, Sequence analy sis of the mouse and human promoter region revealed the presence of tw o palindromic binding elements for homeobox genes of the prd type to w hich goosecoid belongs. We show that Goosecoid protein can bind to the se sites in vitro. By using reporter gene constructs of the human and mouse promoter, we demonstrate that Goosecoid can act as a repressor o f its own promoter activity in transient co-transfection experiments i n mouse P19 cells and in Xenopus embryos. Autorepression depends on th e presence of the homeodomain and is mediated through the prd element more proximal to the transcriptional start site, Our results suggest a role for goosecoid in restricting organizer activity in the vertebrat e gastrula embryo.