A novel POZ/zinc finger protein, champignon, interferes with gastrulation movements in Xenopus

We have cloned a novel krüppel-like transcription factor of Xenopus that encodes POZ/zinc finger protein by expression cloning. Overexpression of mRNA resulted in interference with gastrulation. Because the injected embryo looks like a mushroom in appearance at the neurula stage, we have named this gene champignon (cpg). In cpg-injected embryos, the blastopore appeared normally, but regressed thereafter. The injected embryos then elongated along the primary dorsoventral axis during the tailbud stage. Histologic sections and reverse transcription-polymerase chain reaction analysis showed that cpg had no effect on the cell differentiation. The animal pole region of cpg-injected embryos was thick during the gastrula stage, and mesodermal cells remained in the marginal zone. Furthermore, neither Keller-sandwich explants nor activin-treated animal cap explants excised from cpg-injected embryos elongated. These results suggest that cpg acts as a potent inhibitor of cell migration and cell intercalation during gastrulation.