Résumé
The role of proto-oncogenes in embryonic development was investigated using one of the most characterized vertebrates, the amphibian
Xenopus laevis. Genes which belong to the major proto-oncogene families have been detected in
Xenopus genome. The developmental control of the
myc gene was assayed using a characterized
Xenopus myc probe and specific antibodies. The
myc gene is highly expressed as a stable maternal mRNA in oocyte, and an unfertilized egg contains 5 × 10
5-fold the
myc RNA content of a proliferative somatic cell. The
myc RNA store is evenly distributed in the oocyte and the egg. Fertilization triggers a post-transcriptional control of the gene and the RNA store is progressively degraded to a constitutive value of 10 to 30
myc RNA copies registered per gastrula embryonic cell. The 62K
myc protein is accumulated late in oogenesis. This uncoupling of
myc expression and cell proliferation appears as a specific developmental regulation of the
myc gene, adapted to the series of rapid cell cleavages occurring after fertilization.