NON-CELL AUTONOMOUS INDUCTION OF APOPTOSIS AND LOSS OF POSTERIOR STRUCTURES BY ACTIVATION DOMAIN-SPECIFIC INTERACTIONS OF OCT-1 IN THE XENOPUS EMBRYO

Oct-1, a member of the POU family of transcription factors, is express ed at relatively high levels in ectodermal and mesodermal cell lineage s during early Xenopus embryogenesis (Veenstra et al, 1995). Here we s how that overexpression of Oct-1 induces programmed cell death concomi tant with the loss of the posterior part of the body axis. Truncated O ct-1 variants, missing either the C-terminal or N-terminal trans-activ ation domain, exhibit a different capacity to cause such developmental defects. Oct-1-induced cell death is rescued in unilaterally injected embryos by non-injected cells, indicative of the non-cell autonomous character of the developmental effects of Oct-1. This was confirmed by marker gene analysis, which showed a significant decrease in brachyur yexpression, suggesting that Oct-1 interferes with an FGF-type signall ing pathway.