Figure 1. The interruption of fertilization in Dcst-related gene mutants in different species.

(A) In mammals, sperm mutant for Dcst1 and/or Dcst2 can penetrate the egg coat and contact the egg plasma membrane, but they do not fuse with the egg. (B) In C. elegans, spe-42 or spe-49 mutant sperm can contact the egg plasma membrane, but they do not fuse with the egg. (C) In Drosophila, giant sperm enter the egg through a small opening called a micropyle: however, in snky mutant sperm the plasma membrane of the sperm does not break down, thus blocking nuclear fusion.