A female sterile mutant, unfertilizable (uf), in Xenopus laevis

We describe a female sterile mutant, unfertilizable (uf), in Xenopus laevis whose eggs cannot be fertilized by either natural mating or artificial insemination. The uf eggs were able to be activated by pricking with a fine glass needle. Ultraviolet-solubilized jelly from the uf eggs could permit the fertilization of the dejellied wild-type eggs by artificial insemination, while uv-solubilized jelly from the wild-type eggs did not permit the fertilization of the dejellied uf eggs. The uf eggs, whose jelly coats and vitelline envelopes were removed, could be fertilized by insemination in the uv-solubilized jelly from either wild-type or uf eggs. These results show that the eggs and the jelly coats are intact but the vitelline envelopes are abnormal in uf mutant eggs. One- and two-dimensional gel electrophoretic comparisons of vitelline envelopes from wild-type and uf eggs demonstrated that five protein components, having estimated molecular masses of about 26, 64, 69, 78, and 250 kDa, were present in the vitelline envelopes of uf eggs but were absent in those of wild-type eggs. All of these components were polymorphic in terms of isoelectric points. Thus the cause of unfertilizability of uf eggs resides in the vitelline envelopes whose protein components exceed those of the wild-type eggs.