Overexpression of wild-type p53 interferes with normal development in Xenopus laevis embryos

We have cloned and sequenced a Xenopus p53 homologue which differs by one amino acid deletion from a previously published Xenopus sequence (Soussi et al., 1987). Transcription analysis revealed that this gene is activated during early oogenesis and that zygotic transcription initiates after midblastula transition. Transcripts are also present in all tested tissues of adult animals. Whole mount in situ hybridization with Xenopus oocytes and embryos revealed, that transcripts are ubiquitously distributed although some accumulation is observed in certain tissues. Microinjection of p53 mRNA into early cleavage stages effectively resulted in overexpression of p53 protein and interfered with normal development. Lethal defects until and during gastrulation and aberrant phenotypes of surviving embryos were probably caused by cleavage arrest or cleavage delay of injected cells with subsequent distortions of cell movements, induction processes and tissue differentiations.