Spatial distribution of abundant proteins in oocytes and fertilized eggs of the Mexican axolotl (Ambystoma mexicanum)

Two-dimensional protein patterns were compared from sections along the longitudinal axis of oocytes and fertilized eggs of the Mexican axolotl (Ambystoma mexicanum). Only a few differences were observed between four different sections through both oocyte and fertilized eggs. A set of proteins (14 out of 120 proteins) were found that reside only in the germinal vesicles (GV) of the fully grown oocyte. Two of these were observed exclusively in the vegetal half, and one in the animal half after GV breakdown, while other proteins were randomly distributed within the fertilized egg. One cytoplasmic protein was present only in the vegetal half of the mature oocyte and became present also in the animal half of the fertilized egg. Additional proteins were observed in all transverse sections of both mature oocyte and fertilized eggs. It is proposed that these proteins are modified rather than newly synthesized proteins.