Hereditary abnormal activation in Pleurodeles waltl oocytes.

A mutation which affects the eggs was detected in a Pleurodeles waltl laboratory strain. About 4 to 5 hours after fertilization, i.e. before the first cleavage, mutant eggs exhibited one or more depigmented patches (DP) on the animal hemisphere. Later on, some eggs failed to cleave, or cleaved abnormally. However, if gastrulation was successful, further development occurred normally. Abnormal eggs showed a disorganization of the vitelline gradient as well as a large lens-like zone of hyaline cytoplasm lying under the DP and a heterogeneous distribution of actin and tubulin in the inner cytoplasm. This mutation was named turbulent egg cytoplasm (tec). The alterations described above seem to be related to modifications of the cytoskeleton. Since artificially activated tec ova also exhibited the mutant pattern, we may conclude that the tec phenotype is expressed as a maternal effect syndrome.